Proton exchange membrane water electrolyzer(PEMWE)is crucial for the storage and conversion of renewable energy.However,the harsh anode environment and the oxygen evolution reaction(OER),which involves a four-electron...Proton exchange membrane water electrolyzer(PEMWE)is crucial for the storage and conversion of renewable energy.However,the harsh anode environment and the oxygen evolution reaction(OER),which involves a four-electron transfer,result in a significant overpotential that limits the overall efficiency of hydrogen production.Identifying active sites in the OER is crucial for understanding the reaction mechanism and guiding the development of novel electrocatalysts with high activity,cost-effectiveness,and durability.Herein,we summarize the widely accepted OER mechanism in acidic media,in situ characterization and monitoring of active sites during the reaction,and provide a general understanding of the active sites on various catalysts in the OER,including Ir-based metals,Ir-based oxides,carbon/oxide-supported Ir,Ir-based perovskite oxides,and Ir-based pyrochlore oxides.For each type of electrocatalysts,reaction pathways and actual active sites are proposed based on in situ characterization techniques and theoretical calculations.Finally,the challenges and strategic research directions associated with the design of highly efficient Ir-based electrocatalysts are discussed,offering new insights for the further scientific advancement and practical application of acidic OER.展开更多
Hydrogen production from water electrolysis,in particular from proton exchange membrane water electrolyzers(PEMWE),is a key approach to realizing a carbon-free energy cycle.However,the high anodic potential and strong...Hydrogen production from water electrolysis,in particular from proton exchange membrane water electrolyzers(PEMWE),is a key approach to realizing a carbon-free energy cycle.However,the high anodic potential and strong acid in PEMWE systems pose a major challenge to the stability of electrocatalysts,and the development of efficient and corrosion-resistant catalysts is urgently needed.Currently,iridium(Ir)-based catalysts have gained great attention due to their promising activity and stability,while the extremely low reserves of Ir in the earth seriously hinder the commercialization of PEMWE.Therefore,a systematic understanding of the latest advances in Ir-based catalysts is necessary to guide their rational design to meet the industrial requirements.In this review,the general reaction mechanisms and advanced characterization techniques for mechanism recognition are first introduced.Afterwards,the systematic design strategies and performances of Ir-based catalysts,including metallic Ir,Ir oxides,and Ir-based perovskites,are summarized in detail.Finally,the conclusions,challenges,and prospects for Ir-based electrocatalysts are presented.展开更多
Proton exchange membrane water electrolyzer(PEMWE)technology is regarded as one of the most promising methods for green hydrogen generation.The oxygen evolution reaction(OER)at the anode is the primary bottleneck prev...Proton exchange membrane water electrolyzer(PEMWE)technology is regarded as one of the most promising methods for green hydrogen generation.The oxygen evolution reaction(OER)at the anode is the primary bottleneck preventing the industrial-scale application of PEMWEs due to its sluggish kinetics,and it presently relies upon electrocatalysts that use scarce,costly Ru and Ir.In addition,most of the Ru-and Ir-based electrocatalysts developed to date need high noble metal loading and present good activity only at low current density for a short period.In this review,we systematically elaborate upon various effective strategies for modulating Ruand Ir-based catalysts to achieve large current density,high stability,and high atom economy,including singleatom designs,heteroatom doping,defect/vacancy creation,alloying,and heterojunction engineering.The structure–performance relationships of OER catalysts synthesized using different strategies are elucidated,along with the importance of substrate materials.We conclude by discussing the remaining challenges and future prospects for OER electrocatalysts in acid.展开更多
The present work introduces a novelγ’phasestrengthened Ir-W-Al-Th superalloy for ultrahigh-temperature applications.First,the as-cast microstructure and phase transformation of Ir-13 W-6 Al-0.15 Th(at%)alloy during ...The present work introduces a novelγ’phasestrengthened Ir-W-Al-Th superalloy for ultrahigh-temperature applications.First,the as-cast microstructure and phase transformation of Ir-13 W-6 Al-0.15 Th(at%)alloy during solid solution and aging were investigated.Phase transformation was observed during heat treatment.The primaryγ’phase disappeared via the redissolution ofγ’→γat 1800℃.The recrystallization took place at 1450℃and very fine equiaxedγ’/γgrains formed after240 h.The cold-rolled microstructure indicated that the room-temperature c phase was brittle and cracks mainly emerged along grain boundaries.Ir-13 W-6 Al-0.15 Th alloy exhibited a higher nanohardness than other Ir-based superalloys and pure Ir,which can be attributed to the solid solution and precipitation(γ’)strengthening.In addition,the as-cast Ir-13 W-6 Al-0.15 Th alloy shows a medium room-temperature compressive yield strength and good ductility.展开更多
Iridium(Ir)-based materials are the only commercializable class of anode electrocatalysts for acidic oxygen evolution reaction(OER)in proton exchange membrane water electrolyzers(PEMWE).Intending to large-scale implem...Iridium(Ir)-based materials are the only commercializable class of anode electrocatalysts for acidic oxygen evolution reaction(OER)in proton exchange membrane water electrolyzers(PEMWE).Intending to large-scale implement of PEMWE,it is urgent to improve their OER performances for reducing the usage of high-cost Ir element.Herein,we report an elaborate synthesis of ultrathin Ir/WO_(x)hybrid nanosheets equipped with abundant 2D-confined heterointerfaces(denoted as Ir/WO_(x)NSs),which are composed of ultrathin Ir nanograins embedded in amorphous WO_(x)matrix,to substantially enhance the acidic OER.The Ir/WO_(x)NSs achieve a notable mass activity of 2.34 A mg Ir^(−1)at an overpotential of 300 mV,which is approximately 11.1 and 9.8 times higher than those of Ir NSs and commercial Ir/C,respectively.The 2D-confined interactions between crystalline Ir nanograins and amorphous WO_(x)matrix establish synergistic bifunctional sites and efficient charge transfer interfaces,which effectively accelerate the initial hydrolysis dissociation step.Moreover,on interfacial Ir atoms,the adsorption of*O and subsequent formation of*OOH intermediates are thermodynamically facilitated,making the OER process more favorable through the adsorbate evolution mechanism.Finally,the Ir/WO_(x)NSs based PEMWE demonstrates a low cell voltage of only 1.71 V to deliver 1.0 A cm^(−2)current density as well as an outstanding long-term durability,realizing efficient and stable green hydrogen production.This work highlights the engineering of 2D-confined metal-oxide interfacial electrocatalysts for efficient energy conversion applications.展开更多
Iridium(Ir)-based catalysts are highly efficient for the anodic oxygen evolution reaction(OER)due to high stability and anti-corrosion ability in the strong acid electrolyte.Recently,intensive attention has been direc...Iridium(Ir)-based catalysts are highly efficient for the anodic oxygen evolution reaction(OER)due to high stability and anti-corrosion ability in the strong acid electrolyte.Recently,intensive attention has been directed to novel,efficient,and low-cost Ir-based catalysts to overcome the challenges of their application in the water electrolysis technique.To make a comprehensive understanding of the recently developed Ir-based catalysts and their catalytic properties,the mechanism and catalytic promotion principles of Ir-based catalysts were discussed for OER in the acid condition aimed for the proton exchange membrane water electrolyzer(PEMWE)in this review.The OER catalytic mechanisms of the adsorbate evolution mechanism and the lattice oxygen mechanism were first presented and discussed for easy understanding of the catalytic mechanism;a brief perspective analysis of promotion principles from the aspects of geometric effect,electronic effect,synergistic effect,defect engineering,support effect was concluded.Then,the latest progress and the practical application of Ir-based catalysts were introduced in detail,which was classified into the varied composition of Ir catalyst in terms of alloys,hetero-element doping,perovskite,pyrochlore,heterostructure,core-shell structure,and supported catalysts.Finally,the problems and challenges faced by the current Ir-based catalyst in the acidic electrolyte were put forward.It is concluded that highly efficient catalysts with low Ir loading should be developed in the future,and attention should be paid to probing the structural and performance correlation,and their application in real PEMWE devices.Hopefully,the current effort can be helpful in the catalysis mechanism understanding of Ir-based catalysts for OER,and instructive to the novel efficient catalysts design and fabrication.展开更多
基金supported by Henan Province Science and Technology Research Project(Grant No.242103810058)Natural Science Foundation of Henan(Grant No.252300421104)+3 种基金National Natural Science Foundation of China(Grant No.52102346)Henan Key Research and Development Project(Grant No.231111230100)Heluo Youth Talent Project(Grant No.2024HLTJ14)Henan Postdoctoral Research Initiation Project(Grant No.HN2022040 and HN2022048).
文摘Proton exchange membrane water electrolyzer(PEMWE)is crucial for the storage and conversion of renewable energy.However,the harsh anode environment and the oxygen evolution reaction(OER),which involves a four-electron transfer,result in a significant overpotential that limits the overall efficiency of hydrogen production.Identifying active sites in the OER is crucial for understanding the reaction mechanism and guiding the development of novel electrocatalysts with high activity,cost-effectiveness,and durability.Herein,we summarize the widely accepted OER mechanism in acidic media,in situ characterization and monitoring of active sites during the reaction,and provide a general understanding of the active sites on various catalysts in the OER,including Ir-based metals,Ir-based oxides,carbon/oxide-supported Ir,Ir-based perovskite oxides,and Ir-based pyrochlore oxides.For each type of electrocatalysts,reaction pathways and actual active sites are proposed based on in situ characterization techniques and theoretical calculations.Finally,the challenges and strategic research directions associated with the design of highly efficient Ir-based electrocatalysts are discussed,offering new insights for the further scientific advancement and practical application of acidic OER.
基金supported by the National Natural Science Foundation of China(22202053,22109035,52362031,and 52274297)the start-up Research Foundation of Hainan University(KYQD(ZR)-20008,20083,20084,23068,and 23169)+4 种基金the Hainan Province Science and Technology Special Fund(ZDYF2024SHFZ074)the Collaborative Innovation Center of Marine Science and Technology,Hainan University(XTCX2022HYC04)the specific research fund of The Innovation Platform for Academicians of Hainan Province(YSPTZX202315)the Research Fund Program of Guangdong Provincial Key Laboratory of Fuel Cell Technology(FC202307)the Open Fund Project of Key Laboratory of Electrochemical Energy Storage and Energy Conversion in Hainan Province of China(KFKT2023002)。
文摘Hydrogen production from water electrolysis,in particular from proton exchange membrane water electrolyzers(PEMWE),is a key approach to realizing a carbon-free energy cycle.However,the high anodic potential and strong acid in PEMWE systems pose a major challenge to the stability of electrocatalysts,and the development of efficient and corrosion-resistant catalysts is urgently needed.Currently,iridium(Ir)-based catalysts have gained great attention due to their promising activity and stability,while the extremely low reserves of Ir in the earth seriously hinder the commercialization of PEMWE.Therefore,a systematic understanding of the latest advances in Ir-based catalysts is necessary to guide their rational design to meet the industrial requirements.In this review,the general reaction mechanisms and advanced characterization techniques for mechanism recognition are first introduced.Afterwards,the systematic design strategies and performances of Ir-based catalysts,including metallic Ir,Ir oxides,and Ir-based perovskites,are summarized in detail.Finally,the conclusions,challenges,and prospects for Ir-based electrocatalysts are presented.
基金supported by the National Natural Science Foundation of China(No.U20A20250,22322104,and 22171074)the Heilongjiang Provincial Natural Science Foundation of China(No.YQ2021B009)the Basic Research Fund of Heilongjiang University in Heilongjiang Province(No.2021-KYYWF-0031).
文摘Proton exchange membrane water electrolyzer(PEMWE)technology is regarded as one of the most promising methods for green hydrogen generation.The oxygen evolution reaction(OER)at the anode is the primary bottleneck preventing the industrial-scale application of PEMWEs due to its sluggish kinetics,and it presently relies upon electrocatalysts that use scarce,costly Ru and Ir.In addition,most of the Ru-and Ir-based electrocatalysts developed to date need high noble metal loading and present good activity only at low current density for a short period.In this review,we systematically elaborate upon various effective strategies for modulating Ruand Ir-based catalysts to achieve large current density,high stability,and high atom economy,including singleatom designs,heteroatom doping,defect/vacancy creation,alloying,and heterojunction engineering.The structure–performance relationships of OER catalysts synthesized using different strategies are elucidated,along with the importance of substrate materials.We conclude by discussing the remaining challenges and future prospects for OER electrocatalysts in acid.
基金financially supported by the fund of the National Key R&D Program of China(No.2017YFB0305500)the State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals(No.SKL-SPM-2018010)。
文摘The present work introduces a novelγ’phasestrengthened Ir-W-Al-Th superalloy for ultrahigh-temperature applications.First,the as-cast microstructure and phase transformation of Ir-13 W-6 Al-0.15 Th(at%)alloy during solid solution and aging were investigated.Phase transformation was observed during heat treatment.The primaryγ’phase disappeared via the redissolution ofγ’→γat 1800℃.The recrystallization took place at 1450℃and very fine equiaxedγ’/γgrains formed after240 h.The cold-rolled microstructure indicated that the room-temperature c phase was brittle and cracks mainly emerged along grain boundaries.Ir-13 W-6 Al-0.15 Th alloy exhibited a higher nanohardness than other Ir-based superalloys and pure Ir,which can be attributed to the solid solution and precipitation(γ’)strengthening.In addition,the as-cast Ir-13 W-6 Al-0.15 Th alloy shows a medium room-temperature compressive yield strength and good ductility.
基金supported by the National Natural Science Foundation of China(U24A20563,22171093,22201085)the Natural Science Foundation of Fujian Province(2022J02008)the Scientific Research Funds of Huaqiao University.
文摘Iridium(Ir)-based materials are the only commercializable class of anode electrocatalysts for acidic oxygen evolution reaction(OER)in proton exchange membrane water electrolyzers(PEMWE).Intending to large-scale implement of PEMWE,it is urgent to improve their OER performances for reducing the usage of high-cost Ir element.Herein,we report an elaborate synthesis of ultrathin Ir/WO_(x)hybrid nanosheets equipped with abundant 2D-confined heterointerfaces(denoted as Ir/WO_(x)NSs),which are composed of ultrathin Ir nanograins embedded in amorphous WO_(x)matrix,to substantially enhance the acidic OER.The Ir/WO_(x)NSs achieve a notable mass activity of 2.34 A mg Ir^(−1)at an overpotential of 300 mV,which is approximately 11.1 and 9.8 times higher than those of Ir NSs and commercial Ir/C,respectively.The 2D-confined interactions between crystalline Ir nanograins and amorphous WO_(x)matrix establish synergistic bifunctional sites and efficient charge transfer interfaces,which effectively accelerate the initial hydrolysis dissociation step.Moreover,on interfacial Ir atoms,the adsorption of*O and subsequent formation of*OOH intermediates are thermodynamically facilitated,making the OER process more favorable through the adsorbate evolution mechanism.Finally,the Ir/WO_(x)NSs based PEMWE demonstrates a low cell voltage of only 1.71 V to deliver 1.0 A cm^(−2)current density as well as an outstanding long-term durability,realizing efficient and stable green hydrogen production.This work highlights the engineering of 2D-confined metal-oxide interfacial electrocatalysts for efficient energy conversion applications.
基金This work is supported by the National Natural Science Foundation of China(Nos.21972124 and 22272148),a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institution was also appreciated by the authors.
文摘Iridium(Ir)-based catalysts are highly efficient for the anodic oxygen evolution reaction(OER)due to high stability and anti-corrosion ability in the strong acid electrolyte.Recently,intensive attention has been directed to novel,efficient,and low-cost Ir-based catalysts to overcome the challenges of their application in the water electrolysis technique.To make a comprehensive understanding of the recently developed Ir-based catalysts and their catalytic properties,the mechanism and catalytic promotion principles of Ir-based catalysts were discussed for OER in the acid condition aimed for the proton exchange membrane water electrolyzer(PEMWE)in this review.The OER catalytic mechanisms of the adsorbate evolution mechanism and the lattice oxygen mechanism were first presented and discussed for easy understanding of the catalytic mechanism;a brief perspective analysis of promotion principles from the aspects of geometric effect,electronic effect,synergistic effect,defect engineering,support effect was concluded.Then,the latest progress and the practical application of Ir-based catalysts were introduced in detail,which was classified into the varied composition of Ir catalyst in terms of alloys,hetero-element doping,perovskite,pyrochlore,heterostructure,core-shell structure,and supported catalysts.Finally,the problems and challenges faced by the current Ir-based catalyst in the acidic electrolyte were put forward.It is concluded that highly efficient catalysts with low Ir loading should be developed in the future,and attention should be paid to probing the structural and performance correlation,and their application in real PEMWE devices.Hopefully,the current effort can be helpful in the catalysis mechanism understanding of Ir-based catalysts for OER,and instructive to the novel efficient catalysts design and fabrication.
