AD Leave a rating/comment#Painting#SculptureBack to ArticlesSHARE please click the box below to let us know you're not a robot Get the most important global markets news at your fingertips with a Bloomberg.com subscription Leave a rating/comment#PaintingBack to ArticlesSHARE Metrics details An Author Correction to this article was published on 20 April 2020 This article has been updated Microkinetic analyses of aqueous electrochemistry involving gaseous H2 or O2 oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) The Tafel slopes used to evaluate the rate determining steps generally assume extreme coverage of the adsorbed species (θ ≈ 0 or ≈1) We conducted detailed kinetic analyses describing the coverage-dependent Tafel slopes for the aforementioned reactions Our careful analyses provide a general benchmark for experimentally observed Tafel slopes that can be assigned to specific rate determining steps The Tafel analysis is a powerful tool for discussing the rate determining steps involved in electrocatalysis but our study also demonstrated that overly simplified assumptions led to an inaccurate description of the surface electrocatalysis Tafel analyses have been performed in conjunction with the Butler-Volmer equation where its applicability regarding only electron transfer kinetics is often overlooked Based on the derived kinetic description of the HER/HOR as an example the limitation of Butler-Volmer expression in electrocatalysis is also discussed in this report Both technologies play a crucial role in the future of sustainable societies and thus huge research efforts have been dedicated to improving the electrocatalytic activity of these reactions—HER In the field of electrochemistry38 the electric currents are experimentally measured by applying a potential to electrodes The electric currents are proportional to the reaction rate over the electrodes The electrocatalytic reaction rate is potential-dependent indicating that the rate constant is also potential-dependent Electrocatalytic reactions are generally composed of a number of elementary steps and the forward and backward reaction rates of each electrochemical elementary step are potential-dependent The potential-dependent nature of the electrocatalytic reaction rate is associated with the potential-dependent coverage of the intermediate species (θ) which is related to their formation and consumption rates This report addresses the theoretical description of the kinetics of these fundamental reactions (HER ORR and OER) simply based on microkinetic analyses Our aims were (1) to describe the dependence of the Tafel slope on the coverage of the formed surface species where M is the surface site and (2) to address the applicability of the Butler-Volmer equation in describing electrocatalytic kinetics The visualization of the electrocatalytic kinetics provides the fundamental understanding of the potential-dependent shift in the Tafel slopes associated with the reaction mechanism changes relevant to water electrolysis and fuel cells the Tafel analysis leads to two important physical parameters: the Tafel slope and the exchange current density the following Tafel relation has been well confirmed: T: the absolute temperature) and j0 is the exchange current density The equation represents the total currents from both reduction and oxidation reactions (opposite signs) we consider only forward (or backward) rates that are sufficiently larger than the corresponding backward (or forward) reaction rate for analyzing electrochemical performances the Tafel analysis is conjugated with the Butler-Volmer equation in many studies the Tafel slope can be used to address the elementary steps and the rate determining steps the Tafel slope is discussed based purely on theoretical microkinetic analyses for the hydrogen evolution reaction (HER) the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) the fifth section discusses the rate determining steps of the opposite directions in an oxidation-reduction couple Due to the different rate-determining steps for the respective reactions a good HOR or OER catalyst may not be a good HER or ORR catalyst the Butler-Volmer equation is limited to describing chemically reversible electrocatalytic reactions α = 0.5 and the surface area of the electrode The HER is generally described in two ways A theoretical kinetic description for each reaction is discussed in the following sections Each step can determine the overall rate and therefore we developed three different kinetic expressions in this section When the Volmer step determines the rate, the other steps should not be considered. The forward reaction rate in Equation 6 ri and ki are the reaction rate and rate constant for ith Equation and and θ denote the hydronium ion activities and the surface coverage by the hydrogen atom Because this step is an electron transfer step the kinetic rate constant depends on the applied potential the reaction rate can be described by the following equation: An electric current is correlated with the reaction rate according to the following equation: where I is the electric current, n is the number of electrons involved and A denotes the surface area of the electrocatalyst. Equations 11 and 12 lead to the following expression for the electric current: When the Heyrovsky step is the rate determining step, the adsorbed hydrogen, the reactant for the Heyrovsky step, should be taken into consideration in this case. The forward and reverse reactions of Equation 6 are pre-equilibrated in this case is the same as the forward reaction rate (Equation 9) resulting in the following coverage description: where Ki defines the ratio ki/k−i. The forward reaction rate for Equation 7 is calculated by the following equation: Combining Equations 10, 15 and 16 we obtain the following electric current description: resulting in the following electric current description the Tafel step is not an electron transfer so the potential dependence of the currents originates from that of the coverage water reduction is described by the following three steps: and Equation 8 for the Tafel step three cases involving these steps determining the rate are considered When the Volmer step is rate determining step, the forward reaction rate for Equation 20 corresponds to the overall rate. As discussed in the section for hydronium ion reduction, the surface coverage can be close to zero. Therefore, combining Equations 10 and 22 yields the following current expression: In the case of the Heyrovsky step determining the rate, the Volmer step can be pre-equilibrated, so the reverse reaction rate for Equation 20 is the same as Equation 22 The forward reaction rate in the Heyrovsky step is given as follows: Equations 10, 25 and 26 lead to the following description of the electric currents the electric current is described as follows: These examples demonstrate the significance in considering potential-dependent Tafel slopes even the theoretical Tafel slopes at smaller overpotentials do not reach the well-known values of 30 if too small an overpotential region is considered the Tafel analysis leads to a misrepresentation of the rate-determining step and furthermore poorly compares to other reported values These studies support the importance of evaluating in detail the theoretical Tafel slope as potential-dependent which are the reverse expressions of the HER Hydrogen can be oxidized either by a water molecule or a hydroxide anion Each case determining the overall reaction rate is discussed in the following sections When the Heyrovsky step determines the rate the adsorbed hydrogen is consumed via the Volmer step it is assumed that the Tafel step does not occur or is slow and therefore negligible The forward reaction rate in Equation 7’ is described by the following equation: When the Tafel step is the rate determining step it is assumed that the Heyrovsky step is slow and that the coverage is close to zero Notably, Ki defines the ratio of ki/k−i (not k−i/ki) to be consistent with the HER section. The other coverage expression can be obtained by considering the equilibrium of Equations 18 and 31 we obtain the following electric current expression The elementary steps are given by the following equations: When the Heyrovsky step is rate determining the surface coverage is close to zero and the Volmer step is negligibly slow The forward reaction rate for Equation 21’ is described by the following equation: The assumptions made here and in Equations 10 and 36 give us the following current expression: In the case of the Tafel step determining the rate, the Volmer step description for the HOR with hydroxide anion is equivalent to that for the HOR with water. Therefore, Equation 32 also gives the electric current for this case the electric current for this case is described by the following equation: These examples corroborate the significance of this study: a Tafel slope of around 120 mV dec−1 is frequently reported but is not evidenced in any rate-determining step where M denotes an empty site on the surface. For acidic conditions, the following step is introduced instead of Equations 41 and 42: θ2 and θ3 denote the surface coverage by the empty site When the formation of MOO− is the rate determining step, Equation 40 can be assumed to be at equilibrium. The forward and reverse reaction rates of Equation 40 are the same: where θ0 and θ1 denote the surface coverage by the empty sites and MOO, respectively. Because Equation 41 is rate determining the surface coverage by MOO− is close to zero Equations 45, 46, 47 lead to the following coverage expression: where . The forward reaction rate for Equation 41 is described as The current expression is provided as follows using Equation 10, 48 and 49 respectively, where θ2 denotes the surface coverage by MOO−. Because the forward reaction in Equation 42 determines the overall reaction rate the surface adsorbed species are MOO and MOO− indicating that the following relationship is true: where . The forward reaction rate for Equation 42 is described as Of note, Equation 42 is not an electron transfer reaction and therefore that the reaction rate dependence on the applied potential originates from that of the coverage where θ3 denotes the surface coverage by MO and the following relationship is true: Because the forward reaction rate in Equation 43 is given as This leads to the following equation for the electric current: a variety of Tafel slopes are reported and most are potential-dependent To identify or at least consider the rate determining step deriving the theoretical Tafel slope dependence on each coverage is of particular importance Based on the literature and considering that the OER with hydroxide anion is the backward reaction of the ORR we considered the following mechanism under alkaline conditions θ3 and θ4 denote the surface coverage by the empty site The reaction rate for this case is simply described as follows assuming the coverage of the empty site (θ0) is ≈0 For the electron transfer oxidation reaction, the rate constant is generally described by Equation 10 yielding the following overall kinetic rate equation: In this case, the reaction given by Equation 64 can be assumed to be at equilibrium The kinetic expression of the backward reaction of Equation 64 is: Equations 69 and 72 yield the following relationship: The coverage description is obtained as follows using Equations 73 and 74: The equilibrium of Equation 64 is also applies, indicating that Equation 73 is true. Additionally, Equation 65 is at equilibrium: The backward reaction rate for Equation 65 can be written as: the following relation for the coverage is obtained: Combining Equations 73 gives the following coverage expression: which yields the following kinetic rate equation: This case regarded in a similar manner to the previous case. Considering equilibrium in Equation 66: is true in this case and therefore the following coverage expression is derived by combining Equations 73: Equation 67 at equilibrium corresponds to: Combining with Equation 89 yields the following relation: is true in this case and combining Equations 73 and 93 we obtain the following coverage expression: the kinetic current for this case is given as: (for Equation 77) k67/k68/k−67 = 102/107/1: Fig. 4b (for Equation 84) k67/k68/k69/k−67/k−68 = 104/102/1/109/1: Fig. 4c (for Equation 90) k67/k68/k69/k70/k−67/k−68/k−69 = 3 × 1012/106/104/1/1011/1012/1015: Fig. 4d (for Equation 96) k67/k68/k69/k70/k71/k−67/k−68/k−69/k−70 = 109/1010/108/1011/1/1016/1016/1019/1010: Fig. 4e k67/k68/k69/k70/k71/k−67/k−68/k−69/k−70 = 1011/1014/108/109/1/1014/1014/1019/1010: Fig. 4f To electrochemically elucidate the rate determining step and elementary step not only the smallest Tafel slope but also all measured Tafel slopes should be reported whereby this study can then be used to identify the possible rate determining steps Equation 35 cannot be simplified in this way because the coverage term is potential-dependent Only if we assume a constant coverage can we obtain the combination of Equations 13’ and 35’ leads to the following overall HOR/HER current equation: {(1) if the Volmer step determines both HER and HOR} {(2A) if ε1 is negligibly small compared to ε2 (Tafel-Volmer step) (2B) if K7 is negligibly small compared to (Heyrovsky-Volmer step and θH is close to 0)} {(3) if the surface coverage during hydronium ion reduction remains close to zero at any potential} {(4) if the surface coverage during hydrogen oxidation by water molecules remains close to unity at any potential} then the HOR/HER may be described by the Butler-Volmer equation assuming that the Volmer step determines the rate is difficult in practice A Tafel slope of 120 mV dec−1 for the HER cannot be used as evidence for the Volmer step being the rate-determining step Tafel slopes that differ from 120 mV dec−1 for the HOR can be theoretically obtained only if adsorbed hydrogen species are formed via the Heyrovsky step and if the surface coverage θH is close to 0 These rationales suggest that there are other scenarios in which the Tafel slope can be 120 mV dec−1 an experimentally observed slope of 120 mV dec−1 does not imply that the Volmer step limits the rate there should be a certain potential range where coverage changes with potential the assumption that the Volmer step determines the overall rate at any potential is not true in any case If all of the above criteria are satisfied then the Butler-Volmer equation may be applied to fit the HOR/HER the obtained fitting parameter may result in misleading information Nevertheless, in some studies, the Butler-Volmer equation52: this cannot be always assumed even for the simple electrochemical HER/HOR but can only be assumed for much simpler reactions such as for much more complicated reactions of ORR/OER the applicability of the Butler-Volmer is questionable We conclude that the Butler-Volmer equation cannot be simply applied to any reversible electrocatalytic reaction It can be questioned to what extent evaluating the electrochemical reaction by the exchange current is valid All electrochemical reactions must be evaluated based on the kinetics not in conjunction with the Butler-Volmer equation the kinetics can be evaluated by the Tafel slope but its intercept may not always be equal to the exchange current the rate constant for the chemical reaction follows the Arrhenius’s equation: but this increase likely arises from the increased rate constant When the overall electric current is differentiated by potential the detailed theoretical Tafel slope description is obtained Further differentiating it by temperature reveals the dependence of the Tafel slope on temperature This exercise is highly complicated and beyond the scope of this study The effort to experimentally elucidate the transfer coefficient should be made with considerable care especially considering the applicability of the Butler-Volmer equation where iL is the Levich currents (limiting diffusion current) ω denotes the disk electrode rotation speed ν is the kinematic viscosity and δC represents the difference between surface and bulk reactant concentrations The relationship between the overall current i with the Levich current iL and the kinetic current ik is described in the Koutecky-Levich (KL) equation: Fundamental electrocatalytic reactions of hydrogen evolution reaction (HER) oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were revisited considering conventional microkinetics and focusing on Tafel analyses Our kinetic model reproduces the well-known Tafel slopes of 30 a Tafel slope of 120 mV dec−1 for the HER is generally assigned to the Volmer step this slope was also observed when the Heyrovsky step determined the rate with a high coverage of adsorbed hydrogen (>0.6) a Tafel slope of 120 mV dec−1 was also found for the HOR but not only in the first discharge step as the rate-determining step This observation suggests that a Tafel slope of 120 mV dec−1 (often considered as a single-electron transfer rate limiting) does not conclusively identify the rate-determining step the validity of the Butler-Volmer equation to describe electrocatalytic kinetics in redox reactions was addressed in this study Theoretical modeling suggests that only in very limited cases where the electron transfer reaction determines the rate is the Butler-Volmer equation applicable in describing the electrocatalytic kinetics the kinetics should be considered based on a microkinetic model that includes coverage terms rather than a model conjugated with the Butler-Volmer equation Although the Tafel analysis is useful in elucidating the rate-determining steps such as determination of the kinetics based only on the Butler-Volmer assumption fails to accurately describe the surface electrocatalysis This work provides a more accurate and concrete vision of the kinetics of H2 and O2 aqueous electrocatalysis which is essential for the advancement of electrolysis and fuel cells Insight on Tafel slopes from a microkinetic analysis of aqueous electrocatalysis for energy conversion A correction has been published and is appended to both the HTML and PDF versions of this paper electronegativity and electrochemical behavior of metals Computational high-throughput screening of electrocatalytic materials for hydrogen evolution Enhancing hydrogen evolution activity in water splitting by tailoring Li+-Ni(OH)2-Pt interface Improving the hydrogen oxidation reaction rate by promotion of hydroxyl adsorption Existence of two sets of kinetic parameters in the correlation of the hydrogen electrode reaction Hydrogen diffusion effects on the kinetics of the hydrogen electrode reaction Determination of adsorption of OPD H species in the cathodic hydrogen evolution reaction at Pt in relation to electrocatalysis Hydrogen oxidation and evolution reaction kinetics on carbon supported Pt Rh and Pd electrocatalysts in acidic media Chorkendorff Recent development in hydrogen evolution reaction catalysts and their practical implementation Double perovskites as a family of highly active catalysts for oxygen evolution in alkaline solution Three-dimensional NiFe layered double hydroxide film for high-efficiency oxygen evolution reaction An advanced Ni-Fe layered double hydroxide electrocatalysts for water oxidation benchmarking heterogeneous electrocatalysts for the oxygen evolution reaction Benchmarking hydrogen evolving reaction and oxygen evolving reaction electrocatalysts for solar water splitting devices Activity-stability trends for the oxygen evolution reaction on monometallic oxides in acidic environments Functional links between stability and reactivity of strontium ruthenate single crystals during oxygen evolution Trends in activity for the water electrolyser reaction on 3d M(Ni A perovskite oxide optimized for oxygen evolution catalysis from molecular orbital principles Reaction pathways and poisons-2 The rate controlling step for electrochemical oxidation of hydrogen on Pt in acid and poisoning of the reaction by CO Mechanism of hydrogen oxidation on a platinum-loaded gas diffusion electrode Theoretical calculation of activation energies for Pt + H+(aq) + e−(U) ↔ Pt-H: activation energy-based symmetry factors in the Marcus normal and inverted regions Hydrogen oxidation and evolution on platinum electrodes in base: theoretical study The pH-dependence of the hydrogen exchange current density at smooth platinum in alkaline solution (KOH) Oxygen reduction reaction on Pt and Pt bimetallic surfaces: a selective review Oxygen reduction reaction at Pt single crystals: a critical overview Kinetics and mechanism of O2 reduction at Pt in alkaline solutions Origin of the overpotential for oxygen reduction at a fuel-cell cathode Electrocatalysis of oxygen reduction and small alcohol oxidation in alkaline media Elementary mechanism in electrocatalysis: Revisiting the ORR Tafel slope Activity benchmarks and requirements for Pt Pt-alloy and non-Pt oxygen reduction catalysts for PEMFCs Recent development of non-platinum catalysts for oxygen reduction reaction Highly crystalline multimetallic nanoframes with three-dimensional electrocatalytic surfaces Stabilization of platinum oxygen-reduction electrocatalysts using gold clusters Improved oxygen reduction activity on Pt3Ni(111) via increased surface site availability Pd-Pt bimetallic nanodendrites with high activity for oxygen reduction Kinetics of activation controlled consecutive electrochemical reactions: anodic evolution of oxygen A generalized expression for the Tafel slope and the kinetics of oxygen reduction on noble metals and alloys MoS2 nanoparticles grown on graphene: an advanced catalyst for the hydrogen evolution reaction H2 evolution kinetics at high activity Ni-Mo-Cd electrocoated cathodes and its relation to potential dependence of sorption of H* K inetic analysis of hydrogen evolution at Ni-Mo alloy electrodes Electrode kinetics of oxygen reduction on oxide-free platinum electrodes Pt-oxide coverage-dependent oxygen reduction reaction (ORR) kinetics A comparative study of the oxygen evolution reaction on oxidised nickel Kinetic studies of the oxygen-peroxide couple on pyrolytic graphite Effect of sputtered film of platinum on lower platinum loading electrodes on electrode kinetics of oxygen reduction in proton exchange membrane fuel cells Oxygen electroreduction on titanium-supported thin Pt films in alkaline solution Electrochemical reduction of oxygen at platinum electrodes in KOH solutions –temperature and concentration effects Temperature dependence of the Tafel slope for oxygen reduction on platinum in concentrated phosphoric acid ELECTROCHEMICAL METHOD: Fundamentals and Applications Electrocatalytic activity prediction for hydrogen electrode reaction: intuition Relation of energies and coverage of underpotential and overpotential deposited H at Pt and other metals to the ‘volcano curve’ for cathodic H2 evolution kinetics Advancing the electrochemistry of the hydrogen-evolution reaction through combining experiment and theory Behavior and characterization of kinetically involved chemisorbed intermediates in electrocatalysis of gas evolution reactions Highly active electrocatalysis of the hydrogen evolution reaction by cobalt phosphide nanoparticles The nature of active sites of Ni2P electrocatalysts for hydrogen evolution reaction Hydrogen electrochemistry on platinum lower-index single-crystal surfaces in alkaline solution Temperature-dependent hydrogen electrochemistry on platinum low-index single-crystal surfaces in acid solutions Platinum-rare earth electrodes for hydrogen evolution in alkaline water electrolysis Toward design of synergistically active carbon-based catalysts for electrocatalytic hydrogen evolution Surface polarization matters: enhancing the hydrogen-evolution reaction by shrinking Pt shells in Pt-Pd-Graphene stack structures Enhanced hydrogen evolution catalysis from chemically exfoliated metallic MoS2 nanosheets Identification of active edge sites for electrochemical H2 evolution from MoS2 nanocatalysts earth-abundant catalyst for the hydrogen evolution reaction Widely available active sites on Ni2P for electrochemical hydrogen evolution – insights from first principles calculations Mixed close-packed cobalt molybdenum nitrides as non-noble metal electrocatalysts for the hydrogen evolution reaction Electrocatalysis of the hydrogen oxidation and of the oxygen reduction reaction on Pt and some alloys in alkaline medium Temperature-dependent hydrogen electrochemistry on platinum low-index single-crystal surfaces in acidic solutions Reaction intermediates as a controlling factor in the kinetics and mechanism of oxygen reduction at platinum electrodes Different views regarding the kinetics and mechanism of oxygen reduction at Pt and Pd electrodes Superoxide anion is the intermediate in the oxygen reduction reaction on platinum electrodes Design of oxygen reduction bimetallic catalysts: ab-initio-derived thermodynamic guidelines The mechanism of oxygen reduction at platinum in alkaline solutions with special reference to H2O2 Theory of multiple proton-electron transfer reactions and its implications for electrocatalysis Oxygen electrocatalysis on thin porous coating rotating platinum electrodes Oxygen reduction on a high-surface area Pt/Vulcan carbon catalyst: a thin-film rotating-disk electrode study Oxygen reduction reaction kinetics and mechanism on platinum nanoparticles inside Nafion The oxygen reduction reaction on a Pt/carbon fuel cell catalyst in the presence of chloride anion Study of the kinetics of oxygen reduction on platinum with potential programming of the tip Size effects of platinum particles on the electroreduction of oxygen Electrochemical reduction of oxygen on platinum nanoparticles in alkaline media Mesostructured thin films as electrocatalysts with tunable composition and surface morphology The effect of pH on oxygen and hydrogen peroxide reduction on polycrystalline Pt electrode Sputtered Pt loading of membrane electrode assemblies in proton exchange membrane fuel cells Kinetics and mechanism of the electrochemical reduction of molecular oxygen on platinum in KOH: influence of preferred crystallographic orientation Oxygen reduction reaction on Pt(111): effects of bromide Kinetics of oxygen reduction on Pt(hkl) electrodes: implications for the crystallite size effect with supported Pt electrocatalysts On the kinetics of oxygen reduction on platinum stepped surfaces in acidic media Oxygen reduction on platinum low-index single-crystal surfaces in sulfuric acid solution: rotating ring-Pt(hkl) disk studies Oxygen reduction on platinum low-index single-crysal surfaces in alkaline solution: rotating ring diskPt(hkl) studies Oxygen reduction at Pt and Pt70Ni30 in H2SO4/CH3OH solution Enhancement of the electroreduction of oxygen on Pt alloys with Fe Alloys of platinum and early transition metals as oxygen reduction electrocatalysts PdPt alloy nanocubes as electrocatalysts for oxygen reduction reaction in acid media Kinetics of oxygen reduction at iridium electrodes in aqueous solutions Carbon-supported manganese oxide nanoparticles as electrocatalysts for the oxygen reduction reaction (ORR) in alkaline medium: physical characterizations and ORR mechanism Photochemical route for accessing amorphous metal oxide materials for water oxidation catalysis Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis Oxygen evolution at oxidised iron electrodes: a tale of two slopes Water oxidation on spinel NiCo2O4 nanoneedles anode: microstructures specific surface character and the enhanced electrocatalytic performance ruthenium and their alloys at 80 °C in acid solutions Kinetics of oxygen evolution and dissolution on platinum electrodes Temperature-dependent surface electrochemistry on Pt single crystals in alkaline electrolyte: part 1: CO oxidation Temperature dependent surface electrochemistry on Pt single crystals in alkaline electrolytes Temperature dependent surface electrochemistry on Pt single crystals in alkaline electrolyte Koutecky-Levich analysis applied to nanoparticle modified rotating disk electrodes: electrocatalysis or misinterpretation Study of hydrogen evolution reaction in acid medium on Pt microelectrodes Hydrogen electro reaction: a complete kinetic description Kinetic analysis of the hydrogen electrode reaction in unbuffered media Double-trap kinetic equation for the oxygen reduction reaction on Pt(111) in acidic media Electronic structure of the oxygen-evolving complex in photosystem 2 prior to O-O bond formation Enhancing the alkaline hydrogen evolution reaction activity through the bifunctionality of Ni(OH)2/Metal catalysts Trends in activity for the water electrolkyser reaction on 3d M (Ni Beyond the volcano lilmitations in electrocatalysis - oxygen evolution reaction Enhancing activity for the oxygen evolution reaction: the beneficial interaction of gold with manganese and cobalt oxides Heterogeneous water oxidation: surface activity versus amorphization activation in cobalt phosphate catalysts Water oxidation by amorphous cobalt-based oxides: volume activity and proton transfer to electrolyte bases Download references The research reported in this work was supported by the King Abdullah University of Science and Technology Division of Physical Sciences and Engineering King Abdullah University of Science and Technology (KAUST) performed the derivations and calculation; T.S The authors declare no competing financial interests Download citation Anyone you share the following link with will be able to read this content: a shareable link is not currently available for this article Sign up for the Nature Briefing newsletter — what matters in science An earthquake with a magnitude of 6.6 struck southwestern Japan on Monday with no immediate reports of injury or damage and small tsunami were observed in parts of Miyazaki and Kochi prefectures The agency opened an investigation into potential further seismic activity in the region temblor will not immediately raise the risk of a megaquake a government panel has said could occur in or near the Nankai Trough near the country's Pacific coast The Japan Meteorological Agency launched the examination after issuing its second-ever Nankai Trough Extra Information The latest quake "is not considered to have raised the risk of a Nankai Trough quake" to a relatively high level compared with normal conditions While the jolting occurred beneath the western edge of the hypothesized epicenter of a Nankai Trough quake it was not powerful enough to lead the agency to issue a special alert with the initial estimate of 6.4 adjusted to 6.9 The quake measured a lower 5 on the Japanese seismic intensity scale of 7 in Miyazaki Shintomi and Takanabe in Miyazaki Prefecture many people are frightened by the shaking and seek to hold onto something stable while it lasts A tsunami around 20 centimeters in height was observed in parts of Miyazaki Prefecture while another of about 10 cm was seen in areas of Kochi Prefecture The agency has since lifted all tsunami advisories Service on some parts of the Kyushu Shinkansen bullet train line was temporarily suspended due to the temblor No abnormalities were detected at the Ikata nuclear power plant in Ehime Prefecture or the Sendai nuclear power plant in Kagoshima Prefecture The quake was also felt across wide areas of western Japan Megaquakes in the Nankai Trough that runs along the Pacific coast occur every 100 to 150 years the last being the 1944 Tonankai and 1946 Nankai quakes that together struck a wide area from central to southwestern Japan A magnitude 8 to 9 earthquake has a 70 to 80 percent chance of occurring within 30 years the Japanese government issued a Nankai Trough quake advisory following an M7.1 quake that occurred in the Hyuga Nada Sea the first since the system's implementation in 2017 the government called for caution over the increased risk of strong shaking across a large area following a panel deliberation similar to Monday's While the government urged increased disaster preparedness as opposed to evacuating in anticipation of a megaquake some municipalities in the region have set up evacuation centers and advised elderly residents Japan braces for heavy snow, possible traffic disruption M6.8 quake rocks China's Tibet region, nearly 130 dead To have the latest news and stories delivered to your inbox Simply enter your email address below and an email will be sent through which to complete your subscription Please check your inbox for a confirmation email Thank you for reaching out to us.We will get back to you as soon as possible This website is using a security service to protect itself from online attacks The action you just performed triggered the security solution There are several actions that could trigger this block including submitting a certain word or phrase You can email the site owner to let them know you were blocked Please include what you were doing when this page came up and the Cloudflare Ray ID found at the bottom of this page Metrics details Apart from the discussion about whether fossil fuels will be depleted sooner or later or the tremendous impact of the increase in atmospheric CO2 on the environment solar energy conversion and utilization is intrinsic to meeting energy demands that have been increasing and will continue to increase in coming years efficient devices and systems have been investigated to achieve artificial photosynthesis the use of solar (photon) energy to fuel energetically uphill reactions a consortium involving some Japanese universities and several companies sponsored by METI has been working on a long-term plan to establish strategic novel processes including the chemical process of H2 production from solar energy The water-splitting project is led by Prof Domen at the University of Tokyo whose team has achieved the leading solar energy conversion efficiency values by using novel and creative ideas Photograph of a water-splitting reactor containing a photocatalytic sheet (bottom) under illumination continuous efforts are necessary to achieve a benchmark STH efficiency of 10% The absorption of more photons from the solar spectrum by choosing improved photocatalysts is one potential way to increase the overall efficiency but the strength of the method reported here is that this method can be applied to other photocatalyst powders Scalable water splitting on particulate photocatalyst sheets with a solar-to-hydrogen energy conversion efficiency exceeding 1% Noble-metal/Cr2O3 core/shell nanoparticles as a cocatalyst for photocatalytic overall water splitting Fabrication of a core-shell-type photocatalyst via photodeposition of group IV and V transition metal oxyhydroxides: an effective surface modification method for overall water splitting Photoelectrochemical properties of LaTiO2N electrodes prepared by particle transfer for sunlight-driven water splitting Z-scheme water splitting using particulate semiconductors immobilized onto metal layers for e-cient electron relay Download references KAUST Catalysis Center (KCC) and Physical Sciences and Engineering Division (PSE) The author declares no conflict of interest Reprints and permissions Download citation Metrics details Efficient water vapor splitting opens a new strategy to develop scalable and corrosion-free solar-energy-harvesting systems This study demonstrates highly efficient overall water splitting under vapor feeding using Al-doped SrTiO3 (SrTiO3:Al)-based photocatalyst decorated homogeneously with nano-membrane TiOx or TaOx thin layers (<3 nm) we show the hygroscopic nature of the metal (hydr)oxide layer provides liquid water reaction environment under vapor CoOOH/Rh loaded SrTiO3:Al photocatalyst works for over 100 h and with no problems using simulated seawater as the water vapor supply source This vapor feeding concept is innovative as a high-pressure-tolerant photoreactor and may have value for large-scale applications It allows uniform distribution of the water reactant into the reactor system without the potential risk of removing photocatalyst powders and eluting some dissolved ions from the reactor but they all suffered from the low gas diffusion through the layer or strong corrosion toward the photocatalyst materials a Photographic images of a photocatalyst sheet (1 × 1 cm2) which consists of SrTiO3:Al-based particulate photocatalysts immobilized on a frosted glass substrate b Time course measurement of H2 and O2 gas evolution rate using CoOOH/Rh loaded SrTiO3:Al coated with TiOx under various light intensity The fed gas was Ar with saturated water vapor at 24 °C (10 mL min−1 c H2 evolution rate of various cocatalysts loaded SrTiO3:Al irradiated with 370 nm LED (5.1 mW cm−2) under saturated water vapor balanced with Ar at 24 °C (10 mL min−1 Error bars are standard error from other samples (n = 3–11) d Dependence of H2 evolution rate of CoOOH/Rh loaded SrTiO3:Al coated with TiOx (blue circle) and without TiOx (green square) under various O2 partial pressure ranged from 0 to 33 kPa under 370 nm LED (5.1 mW cm−2) The feed gas was Ar with saturated water vapor at 24 °C the ratio of H2 and O2 evolution was maintained at nearly 1:2 thus showing that the electrons and holes were consumed by the water splitting reaction; no other side reaction occurred When the light intensity was lower than 25 mW cm−2 the gas evolution rate was stable with the time on stream the rate gradually decreased under higher intensity light irradiation (>59 mW cm−2) The cause of decrease in AQY as the function of light intensity as well as decrease in formation rate with time will be discussed in the characterization of oxide thin-layer section The experiments described hereafter were performed under a light intensity of approximately 5 mW cm−2 which corresponds to the actual intensity of UV light in AM 1.5G solar light Figure 2b also shows that the H2 evolution rate reached to ~150 μmol h−1 per 1 cm2 photocatalyst sheet demonstrating the applicability of the TiOx coating for improved photocatalysts where solar-to-hydrogen (STH) efficiency of 10% (corresponding to a hydrogen production rate of 150 μmol h−1 per 1 cm2) is achievable This demonstration suggested that this H2 production system is not limited by water vapor supply even if the H2 evolution rate is corresponding to the rate of 10% STH The partial pressure of H2 in the outlet gas was estimated to be 0.56 kPa Enhanced AQY was not observed in the case of a physical mixture of CoOOH/Rh loaded SrTiO3:Al and TiO2 nanoparticles (P25) The apparent H2 evolution rate immediately reached zero in the presence of 4% O2 using CoOOH/Rh loaded SrTiO3:Al photocatalyst without TiOx layer in the case of CoOOH/Rh loaded SrTiO3:Al photocatalyst with TiOx layer the AQY was maintained above 40% even in the presence of 20% O2 TiOx layer has the role of preventing the reverse water-forming reaction even under O2 presence a Bright field STEM image of CoOOH/Rh loaded SrTiO3:Al coated with TiOx and b its corresponding overlayed EDS mapping of Ti and Sr c Water adsorption isotherm of CoOOH/Rh loaded SrTiO3:Al coated with or without TiOx d Dependence of H2 evolution rate of CoOOH/Rh loaded SrTiO3:Al coated with TiOx on relative humidity at 24 °C (blue circle) Error bars are standard error from other samples (n = 3) The isotherm of TiOx coated CoOOH/Rh loaded SrTiO3:Al showed type-II isotherm and the liquid-like water should exist on the photocatalyst surface under relative humidity values higher than 0.6 the photocatalyst can exhibit water splitting performance under vapor feeding similar to when the photocatalyst is immersed in liquid water the role of the coated TiOx is mitigation of the loss in the elementary reaction step (6) as well as mass transfer of reactants during the overall photocatalytic reaction the reaction rate at 80 °C did not recover even when the humidity returned from 0.1 to 1 thus suggesting that the TiOx covering layer was irreversibly restructured a Dark field TEM image of CoOOH/Rh loaded SrTiO3:Al coated with TaOx and b its corresponding EDS mapping of Ta c H2 evolution rate of TaOx coated SrTiO3:Al type photocatalysts before and after thermal treatment and regeneration process These demonstrations were under saturated water vapor balanced with Ar at 24 °C (10 mL min−1 d Dependence of H2 evolution rate of CoOOH/Rh loaded SrTiO3:Al coated with TaOx on relative humidity at 24 °C e Fourier transformed Ta LIII EXAFS patterns of CoOOH/Rh loaded SrTiO3:Al coated with TaOx recorded at 24 °C under dried condition (dashed) and (solid) after thermal treatment and f corresponding XANES region of Ta LIII XAFS spectra of TaOx coated a Durability test of CoOOH/Rh loaded SrTiO3:Al coated with TiOx under saturated water vapor feeding balanced with Ar at 24 °C (10 mL min−1 The light source was a simulated sunlight (AM 1.5G) b The overall water splitting rate of CoOOH/Rh loaded SrTiO3:Al coated with TiOx under water vapor feeding supplied from ultrapure water or brine (3 wt% NaClaq) balanced with Ar at 24 °C c Photographic images of a vaper feeding photocatalytic overall water splitting system under pressurized condition d H2 evolution rate of CoOOH/Rh loaded SrTiO3:Al coated with TiOx under pressurized condition at total pressure (Ptot) of 0.1 or 0.3 MPa using the system shown in panel c The light source was simulated sunlight (AM 1.5G) There was no significant decrease in the rate of water splitting under vapor feeding at 0.3 MPa versus that at 0.1 MPa An apparent quantum yield of 54 ± 4% with 370 nm LED light for water splitting reaction under vapor feeding was achieved using Cr-free CoOOH and Rh co-deposited SrTiO3:Al with uniformly coated metal (Ti or Ta) (hydr)oxide thin layers This surface nano-membrane coating captures sufficient amount of water vapor thus generating the liquid environment at the surface of SrTiO3:Al The relative humidity pins the photocatalytic performance at each reaction temperature a comparable AQY in water can be achieved under vapor feeding The solar-to-hydrogen efficiency was maintained at around 0.4% for 100 h of long operation and seawater as the water vapor source did not affect the performance These data suggest a new design for efficient and scalable solar H2 production systems using the ambient humidity in a seawater feedstock The SrTiO3 doped with Al (SrTiO3:Al) was synthesized via a previously reported method25 SrTiO3 (FUJIFILM Wako Pure Chemical Corporation) was mixed with SrCl2 (Kanto Chemical Co. Inc.) and Al2O3 (MilliporeSigma) by grinding in an agate mortar at a molar ratio of 10:0.02:1 The resulting mixture was moved into an alumina crucible and then allowed to cool to room temperature The product was separated from unreacted SrCl2 and the resulting powder was then washed with massive amounts of distilled water using ultrasonication until the Cl− ions were not detected in the supernatant The powder was obtained by suction filtration and dried in an oven at 60 °C overnight to obtain a white powder (SrTiO3:Al) The SrTiO3:Al (0.3 g) was dispersed in ultrapure water (3.34 mL) and then 0.1 M Na3RhCl6 (Mitsuwa Chemicals Co. Ltd.) aqueous solution (50 μL) and 0.05 M Cr(NO3)3 (MilliporeSigma) aqueous solution (22.5 μL) were added to the suspension After mixing with ultrasonication for 5 min the suspension was stirred at elevated temperature (~100 °C) using a glass rod until the solution was completely evaporated RhCrOx (imp) loaded SrTiO3:Al was obtained after calcining at 350 °C for 1 h with a ramping rate of 10 °C min−1 Ltd.) aqueous solution (50 μL) was added and then irradiated with LED light as above for 5 min followed by the addition of 85 mM Co(NO3)2 aqueous solution (10 μL) and another 5-min irradiation The solvent was not exchanged during this multistep photodeposition titanium tetraisopropoxide (FUJIFILM Wako Pure Chemical Corporation 37 μmol) with 30 vol% H2O2 (FUJIFILM Wako Pure Chemical Corporation 3.2 mmol) was added into the suspension containing SrTiO3:Al loaded with Rh This was then mixed via ultrasonication for 5 min 1 M NaOH aqueous solution (74.6 μL) was added to the solution where the ratio between the added Na+ versus Ti contained in titanium tetraisopropoxide was 2:1 22 μmol) with 30 vol% H2O2 (FUJIFILM Wako Pure Chemical Corporation 8.0 μmol) was added to the suspension containing the SrTiO3:Al loaded with Rh This was then mixed with ultrasonication for 5 min 1 M NaOH aqueous solution (113 μL) was added to the solution where the ratio between the added Na+ versus Ta contained in tantalum(V) chloride was 5:1 The resulting suspension was irradiated with 370 nm LED (730 mW) for 12 h and then the precipitates were separated by filtration and washed with ethanol three times The collected slurry was not dried further X-ray diffraction (XRD) patterns were collected using RINT-UltimaIII (Rigaku Corporation) with a Cu Kα X-ray radiation source (λ =  0.154056 nm) at a scan rate of 30° min–1 The X-ray photoelectron spectroscopy (XPS) measurements were performed on PHI5000 VersaProbe (ULVAC Inc.) with an Al–Kα source operating at 5 kV STEM images were collected using JEM-2800 transmission electron microscopes (JEOL Ltd.) or Talos 200kV-FE-(S)TEM with super X XDS (Thermo Fisher Scientific Inc.) operating at 200 kV in conjunction with EDS using an X-MAX 100TLE SDD detector (Oxford Instruments) Water adsorption tests and N2 adsorption tests were performed on a 3Flex gas adsorption measurement device (Micromeritics Instrument Corp.) The samples were pretreated at 60 °C for 12 h under vacuum The adsorbed gas amount was measured at the equilibrium point where the pressure change becomes less than 0.01% within 30 s Diffuse reflectance infrared Fourier transform spectra (DRIFTS) were recorded on an FT/IR-6600 (JASCO Corporation) equipped with a heat-vacuum diffuse reflection cell (S.T Pelletized powder samples were placed at the focal point of an integrating sphere After drying at 60 °C for 1 h under vacuum conditions the samples were cooled to room temperature under dry Ar (20 mL min–1) and baseline collection was then performed Ar with saturated H2O or D2O vapor (20 mL min–1) was fed into the cell for 30 min UV–Vis diffuse reflectance spectrum of samples was recorded using a V-770 UV-Vis spectrometer (JASCO Corporation) equipped with an integrating sphere (JASCO Corporation ISN-923) and a spectralon block as a reference to adjust the 100% reflectance level and set the reflectance of the sample holder to 0% Photocatalytic reactions were carried out in the continuous gas flow reactor (Supplementary Fig. 1a) Each synthesized catalyst powder was dispersed in a tiny amount of ultrapure water dropped onto a frosted glass plate (SCHOTT Corp and then dried at 60 °C for 10 min using a hotplate The loaded amount of the photocatalyst was 5 mg per 1 cm2 of the glass plate The prepared photocatalyst sheet was placed at the bottom of a cylindrical reactor made of stainless steel with an internal volume of 38 cm3 Water vapor was supplied to the reactor with Ar gas through a water bubbler which was filled with ultrapure water or brine (3 wt% NaCl aqueous solution) In the pipeline between the water bubbler and the reactor a hygrothermograph (Bosch BME280) was inserted For the activity test under controlled temperature and relative humidity and the water bubbler were placed in a heating oven and the relative humidity of the supplied water vapor was controlled by changing the ratio of the flow rate of the dry Ar and the wet Ar To estimate the effect of O2 addition in inlet gas a O2/Ar mixture with a defined ratio was introduced into the water bubbler and then supplied to the reactor The photocatalyst sheet was irradiated with a 370-nm LED (Asahi Spectra Co. Ltd.; CL-1501) equipped with rod lens (RLQL80-05) to provide a square-shaped light with uniform intensity or simulated sunlight (Asahi Spectra Co.; AM1.5 G solar simulator HAL-320) through a window on top of the reactor The amount of generated H2 and O2 gases were measured using gas chromatography (GC-8A; Shimadzu Co.) equipped with a 5 Å molecular sieve column and a thermal conductivity detector The apparent quantum yield (AQY) for overall water splitting under LED excitation with a center wavelength of 370 nm was calculated according to the following equation: The solar to hydrogen (STH) efficiency for overall water splitting under simulated sunlight was determined according to the following equation and S denote the reaction Gibbs energy of the water splitting reaction H2O(l)→ H2(g) + 1/2O2(g) (237 kJ mol−1 at 288 K) the energy intensity of AM 1.5G solar irradiation (100 mW cm−2) X-ray absorption fine structure (XAFS) of Ta LIII edge in TaOx coated SrTiO3:Al loaded with CoOOH/Rh was measured at BL01B1 beamline at SPring-8 synchrotron facility (Hyogo Japan) using a ring energy of 8 GeV (proposal No The incident X-ray was monochromated using Si(111) double crystal and the energy was calibrated using a Ta foil A pelletized sample (φ7mm) of TaOx coated SrTiO3:Al loaded with CoOOH/Rh was placed in a quartz cell with polyimide windows connected to a N2 gas cylinder After pretreating under dry N2 flow (100 mL min–1) for 30 min N2 containing saturated water vapor was then introduced Spectral measurements were then performed after 30 min The sample was then further treated at 250 °C under dry N2 flow followed by spectral measurements under dry and wet N2 flow at room temperature a Fourier transformation of the EXAFS oscillation was performed between 3 and 14 Å−1 with k-weight of 2 Peak fittings of the EXAFS results were performed using FEFF code Debye–Waller factor (σ2) and the interatomic distance of Ta and O (R) were calculated from the fitting A Taylor-made acrylic reactor with an internal volume of 200 cm3 (Fig. 5c) was used to demonstrate the overall water splitting under water vapor feeding at pressurized conditions The reactor was filled with ultrapure water and the glass pedestal floated in the water The photocatalyst sheet (4 × 4 cm2) immobilized a TiOx coating on the SrTiO3:Al loaded with Rh and CoOOH; this was placed on the pedestal the photocatalyst sheet was placed above the water level The inlet N2 gas flow (50 mL min1) was introduced into the gas phase inside the acrylic(reactor through the filled liquid water the relative humidity in the gas phase inside the acrylic reactor was almost unity The total pressure in the gas phase inside the acrylic reactor was controlled from 0.1 to 0.3 MPa using a back pressure regulator placed downstream of the reactor The photocatalyst sheet was irradiated with simulated sunlight (AM 1.5G) from the top The amount of generated H2 was measured by gas chromatography (Agilent 490 Micro GC) All data supporting the findings of this study are available within this article and its Supplementary Information Source data that support the findings of this study are available from the corresponding author upon reasonable request Correspondence and requests for materials should be addressed to Takanabe Earth-abundant cocatalysts for semiconductor-based photocatalytic water splitting Recent advances in semiconductors for photocatalytic and photoelectrochemical water splitting Technical and economic feasibility of centralized facilities for solar hydrogen production via photocatalysis and photoelectrochemistry Particulate photocatalysts for overall water splitting Photocatalytic solar hydrogen production from water on a 100-m2 scale Scalable water splitting on particulate photocatalyst sheets with a solar-to-hydrogen energy conversion efficiency exceeding 1 Maximizing oxygen evolution performance on a transparent NiFeOx/Ta3N5 photoelectrode fabricated on an insulator Fundamental problems of water splitting at cadmium sulfide Photocorrosion inhibition of CdS-based catalysts for photocatalytic overall water splitting Photocatalytic water splitting using modified GaN:ZnO solid solution under visible light: long-time operation and regeneration of activity A particulate photocatalyst water-splitting panel for large-scale solar hydrogen generation Photocatalytic hydrogen production under water vapor feeding—a minireview Photolysis of water and photoreduction of nitrogen on titanium dioxide Study of the photocatalytic decomposition of water vapor over a nickel(II) oxide-strontium titanate (SrTiO3) catalyst Gas phase photocatalytic water splitting with Rh2-yCryO3/GaN:ZnO in μ-reactors Gas phase photocatalytic water splitting of moisture in ambient air: Toward reagent-free hydrogen production Contribution of electrolyte in nanoscale electrolysis of pure and buffered water by particulate photocatalysis Surface water dependent properties of sulfur-rich molybdenum sulfides: electrolyteless gas phase water splitting A hybrid artificial photocatalysis system splits atmospheric water for simultaneous dehumidification and power generation Photocatalytic water decomposition and water-gas shift reactions over NaOH-coated Fabrication of a core–shell-type photocatalyst via photodeposition of group IV and V transition metal oxyhydroxides: an effective surface modification method for overall water splitting The influence of acceptor and donor doping on the protonic surface conduction of TiO2 SPEEK-TiO2 nanocomposite hybrid proton conductive membranes via in situ mixed sol–gel process Photocatalytic water splitting with a quantum efficiency of almost unity An Al-doped SrTiO3 photocatalyst maintaining sunlight-driven overall water splitting activity for over 1000 h of constant illumination Suppression of the water splitting back reaction on GaN:ZnO photocatalysts loaded with core/shell cocatalysts and Raman scattering analysis of amorphous tantalum oxide with a large extent of oxygen nonstoichiometry Metal-free efficient photocatalyst for stable visible water splitting via a two-electron pathway Solar hydrogen production from seawater vapor electrolysis Download references This work is financially supported by the Artificial Photosynthesis Project (ARPChem) of the New Energy and Industrial Technology Development Organization (NEDO) and the Mohammed bin Salman Center for Future Science and Technology for Saudi-Japan Vision 2030 at The University of Tokyo (MbSC2030) We would like to thank Advanced Characterization Nanotechnology Platform in the Nanotechnology Platform Project sponsored By the Ministry of Education (JPMXP09-A-21-UT-0046) for TEM observations Research Initiative for Supra-Materials (RISM) carried out the materials synthesis and all the experiments except for TEM measurements and a vaper feeding photocatalytic overall water splitting test under pressurized condition conducted a vaper feeding photocatalytic overall water splitting test under pressurized condition and provided the TEM image of CoOOH/Rh loaded SrTiO3:Al coated with TaOx contributed the TEM measurement for CoOOH/Rh loaded SrTiO3:Al coated with TiOx contributed to the synthesis of the materials and validity of experimental results All authors contributed to the discussion of results and commented on the manuscript The authors declare no competing interests Nature Communications thanks Paul Maggard and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Download citation DOI: https://doi.org/10.1038/s41467-022-33439-x Sorry, a shareable link is not currently available for this article. Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily. Malakas made landfall in Kyushu in the early hours of 20 September bringing winds of up to 180 km per hour as well as torrential rain According to figures from Japan Meteorological Agency (JMA) in a 24 hour period between 19 and 20 September Almost 80 mm of rain fell in 1 hour from around 23:00 on 19 September The town of Takanabe saw 123 mm fall in two hours between 19:00 and 21:00 on 19 September Takanabe recorded 310 mm in 24 hours to 09:00 on 20 September The city of Miyazaki recorded 370 mm in 24 hours and prompted local authorities to issue evacuation advisories for more than 600,000 residents in 6 prefectures It is not clear how many people followed the advisories Power outages affected more than 30,000 buildings Six people had to be rescued from flooded buildings Streets and farmland were flooded and roads washed out No deaths or serious injuries have been reported Malakas has since been downgraded to a tropical storm although some further heavy rain is expected and red level weather warnings from JMA remain in place for parts of central Japan Malakas is expected to head northeast along Japan’s Pacific coast before going out into the Pacific Ocean by early Wednesday morning when it will likely be downgraded to a depression Malakas is the sixth to make landfall this year in Japan. At least 11 people died in Japan earlier this month amid disruptions brought by Typhoon Lionrock Lionrock was also thought to have caused the torrential rain and flooding currently affecting northern areas of North Korea Breaking NewsJapan Richard Davies is the founder of floodlist.com and reports on flooding news Europe’s Cities Must Step Up Adaptation Efforts, Says EEA Floods in Florida Led to Increase in Respiratory Problems, Study Says Cookies | Privacy | Contacts © Copyright 2025 FloodList King Abdullah University of Science & Technology (KAUST) A novel molybdenum-coated catalyst that can efficiently split water in acidic electrolytes is developed by researchers at KAUST and could help with efficient production of hydrogen hydrogen is converted into water and heat to make an entirely clean power source there is an urgent need for a sustainable and efficient means of producing it One way is to split water using a process known as photocatalytic hydrogen evolution: water molecules are split into hydrogen and oxygen using only sunlight to provide the necessary energy hydrogen acts as a means of storing solar energy Scientists are searching for ways of improving this water-splitting reaction by developing an optimal catalyst While many different materials have been tried they are usually adversely affected by the oxygen that is also created alongside the hydrogen during the process The two gaseous products can easily recombine back to water due to reverse water-forming reactions Angel Garcia-Esparza and Tatsuya Shinagawa--two former KAUST Ph.D students as leading researchers supervised by Associate Professor of Chemical Science Kazuhiro Takanabe--collaborated with other colleagues from the Catalysis Center and other specialists in the University to create a hydrogen-evolution reaction catalyst that is both acid-tolerant and selectively prevents the water-reforming reaction1 "The development of acid-tolerant catalysts is an important challenge because most materials are not stable and quickly degrade in the acidic conditions that are favorable for hydrogen generation," says Garcia-Esparza Because the acidity of the solution was crucial for the stability of the material the team took the time to establish the optimal pH level between 1.1 and 4.9 They then electro-coated molybdenum onto a standard platinum electrode catalyst in a mildly acidic solution Comparing the performance of the photocatalyst with and without the molybdenum coating the team showed that without molybdenum the rate of hydrogen production eventually plateaued after 10 hours of operation under illumination by ultraviolet light the introduction of molybdenum prevented this fall in performance The researchers believe that this is because the molybdenum acts as a gas membrane preventing oxygen from reaching the platinum and disrupting its catalytic performance "The main challenge for most catalysts is the long-term stability of the materials" explained Garcia-Esparza "So it is an important step to have an acid-tolerant material capable of preventing the water-forming back reaction that slows down water splitting." 10.1002/anie.201701861 are not responsible for the accuracy of news releases posted to EurekAlert by contributing institutions or for the use of any information through the EurekAlert system Copyright © 2025 by the American Association for the Advancement of Science (AAAS) An earthquake measuring an intensity of lower 5 on the Japanese seismic scale of 7 occurred in Miyazaki Prefecture at around 9:19 p.m according to the Japan Meteorological Agency please disable the ad blocking feature and reload the page This website uses cookies to collect information about your visit for purposes such as showing you personalized ads and content By clicking “Accept all,” you will allow the use of these cookies Users accessing this site from EEA countries and UK are unable to view this site without your consent Takanabe and Shintomi in the prefecture saw an intensity of lower 5 The magnitude was 6.9 and the focus was at a depth of about 30 kilometers off the prefecture Tsunami advisories were issued for Miyazaki and Kochi prefectures at 9:29 p.m. A 20 centimeters tsunami was observed at Miyazaki Port at 9:48 pm and a 20 centimeters tsunami in Nichinan at 10:04 p.m Nankai Trough Earthquake Extra Information Issued After Major Quake in Miyazaki Pref.; JMA Concludes Risk of Megaquake Low Magnitude 6.9 Earthquake Rattles Southwestern Japan, Followed by Tsunami Warnings Our weekly ePaper presents the most noteworthy recent topics in an exciting © 2025 The Japan News - by The Yomiuri Shimbun Please view the main text area of the page by skipping the main menu. 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