The lattice-oxygen-mediated mechanism is considered as a reasonable mechanism for the electrochemical catalytic oxygen evolution reaction(OER)of NiFe layered double hydroxides(LDHs).A NiFe LDH with distinct lattice co...The lattice-oxygen-mediated mechanism is considered as a reasonable mechanism for the electrochemical catalytic oxygen evolution reaction(OER)of NiFe layered double hydroxides(LDHs).A NiFe LDH with distinct lattice contraction and microcrystallization was synthesized via a simple one-step method using sodium gluconate.The lattice contraction is attributed to the interaction of carbon in sodium gluconate and iron in NiFe LDH.The NiFe LDH with optimized microcrystallization and lattice contraction shows a low overpotential of 217 mV at a current density of 10 mA cm^(−2) and excellent durability of 20 h at a high current density of 100 mA cm^(−2).The results revealed that a contractive metal–oxygen bond could boost the intrinsic activity of active sites and the microcrystallization promotes an increase in the number of active sites in terms of unit area.The chemical environment of oxygen elemental characterization and resistance at different chronopotentiometry times confirm that the lattice oxygen element is indeed involved in the process of OER,supporting the lattice-oxygen-mediated mechanism of NiFe LDH.Density functional theory calculations reveal that contractive metal–oxygen bonds induced a reduction of the adsorption energy barrier of intermediate products,thus improving the intrinsic catalytic activity.The special characteristics of microcrystallization and lattice contraction of NiFe LDH provide a strategy to improve both the number and the intrinsic activity of active sites in a versatile manner.展开更多
Developing effective and practical electrocatalyst under industrial electrolysis conditions is critical for renewable hydrogen production.Herein,we report the self-supporting NiFe LDH-MoS_(x) integrated electrode for ...Developing effective and practical electrocatalyst under industrial electrolysis conditions is critical for renewable hydrogen production.Herein,we report the self-supporting NiFe LDH-MoS_(x) integrated electrode for water oxidation under normal alkaline test condition(1 M KOH at 25℃)and simulated industrial electrolysis conditions(5 M KOH at 65℃).Such optimized electrode exhibits excellent oxygen evolution reaction(OER)performance with overpotential of 195 and 290 mV at current density of 100 and 400 mA·cm^(-2) under normal alkaline test condition.Notably,only over-potential of 156 and 201 mV were required to achieve the current density of 100 and 400mA·cm^(-2) under simulated industrial electrolysis conditions.No significant degradations were observed after long-term durability tests for both conditions.When using in two-electrode system,the operational voltages of 1.44 and 1.72 V were required to achieve a current density of 10 and 100 mA·cm^(-2) for the overall water splitting test(NiFe LDH-MoS_(x)/INF||20%Pt/C).Additionally,the operational voltage of employing NiFe LDH-MoS_(x)/INF as both cathode and anode merely require 1.52 V at 50mA·cm^(-2) at simulated industrial electrolysis conditions.Notably,a membrane electrode assembly(MEA)for anion exchange membrane water electrolysis(AEMWEs)using NiFe LDH-MoS_(x)/INF as an anode catalyst exhibited an energy conversion efficiency of 71.8%at current density of 400 mA·cm^(-2)in 1 M KOH at 60℃.Further experimental results reveal that sulfurized substrate not only improved the conductivity of NiFe LDH,but also regulated its electronic configurations and atomic composition,leading to the excellent activity.The easy-obtained and cost-effective integrated electrodes are expected to meet the large-scale application of industrial water electrolysis.展开更多
Owing to the significant potential of alkalin seawater electrolysis for converting surplus power into eco friendly hydrogen fuel,we developed bifunctional elec trodes that integrate low-crystalline NiFe LDHs and amorp...Owing to the significant potential of alkalin seawater electrolysis for converting surplus power into eco friendly hydrogen fuel,we developed bifunctional elec trodes that integrate low-crystalline NiFe LDHs and amorphous NiFe alloy on a Ni foam(NF)substrate to enhance this process.Driven by the battery-like charac teristics of NiFe LDHs,an anti-corrosive and active oute layer of NiFe^(vac)OOH continuously forms over time in th hybrid on the anode for the oxygen evolution reaction(OER),effectively mitigating powder shedding caused by corrosion induced by multiple anions in seawater.Mean while,the strong bond between the hybrid and the NF substrate maintains intact hybrid coatings to ensure a rel atively high overall conductivity of the electrodes,signif icantly reducing the negative effects of structura degradation during the OER and hydrogen evolution reaction(HER),as well as the accumulation of contami nants on the electrode surfaces.In long-term tests,thes bifunctionalhybridelectrodesmaintained stable performance,even at a high current density o500 mA·cm^(-2).The cell voltage increased by only 88 m V over 1000 h to 1.970 V during saline electrolysis and by103 mV over 500 h to 2.062 V during seawater electroly sis.Hence,this study provides valuable insights into efficient and stable seawater electrolysis using NiFe LDHs–NiFe alloy hybrids.展开更多
Nickel-iron layered double hydroxides(NiFe LDHs)represent a promising candidate for oxygen evolution reaction(OER),however,are still confronted with insufficient activity,due to the slow kinetics of electrooxidation o...Nickel-iron layered double hydroxides(NiFe LDHs)represent a promising candidate for oxygen evolution reaction(OER),however,are still confronted with insufficient activity,due to the slow kinetics of electrooxidation of Ni^(2+)cations for the high-valent active sites.Herein,nanopore-rich NiFe LDH(PR-NiFe LDH)nanosheets were proposed for enhancing the OER activity together with stability.In the designed catalyst,the confined nanopores create abundant unsaturated Ni sites at edges,and decrease the migration distance of protons down to the scale of their mean free path,thus promoting the formation of high-valent Ni^(3+)/^(4+)active sites.The unique configuration further improves the OER stability by releasing the lattice stress and accelerating the neutralization of the local acidity during the phase transformation.Thus,the optimized PR-NiFe LDH catalysts exhibit an ultralow overpotential of 278 mV at 10 mA∙cm^(−2)and a small Tafel slope of 75 mV∙dec^(−1),which are competitive among the advanced LDHs based catalysts.Moreover,the RP-NiFe LDH catalyst was implemented in anion exchange membrane(AEM)water electrolyzer devices and operated steadily at a high catalytic current of 2 A over 80 h.These results demonstrated that PR-NiFe LDH could be a viable candidate for the practical electrolyzer.This concept also provides valuable insights into the design of other catalysts for OER and beyond.展开更多
NiFe layered double hydroxides(NiFe LDHs)have been intensively developed for the oxygen evolution reaction(OER)in alkaline media;however,their unsatisfactory hydrogen evolution reaction(HER)performance limits their pr...NiFe layered double hydroxides(NiFe LDHs)have been intensively developed for the oxygen evolution reaction(OER)in alkaline media;however,their unsatisfactory hydrogen evolution reaction(HER)performance limits their practical application in overall water splitting.Herein,a simple and efficient one-step electrodeposition method is used to accomplish in situ growth of NiFe LDHsNiFe alloy gradient hybrid coatings on a carbon cloth(CC).Within the binder-free electrode,NiFe LDHs nanosheets with a low-crystalline nature exhibit highly active bifunctional OER/HER activities,and the NiFe alloy acts as a stable electron highway and strong skeleton bridge between NiFe LDHs and the CC.When the electrodes are simultaneously employed as the cathode and anode for overall water splitting,they require low cell potentials of 1.441 V at10 mA·cm^(-2)and 1.703 V at 100 mA·cm^(-2),respectively,and they demonstrate outstanding stability at a current density greater than 100 mA·cm^(-2)for more than 100 h.This is one of the best bifunctional OER and HER catalysts for overall water splitting.Both lattice defects and surface reconstructions crucially contribute to the bifunctional OER/HER activities of NiFe LDHs.This simple and scalable synthesis approach presents an intriguing paradigm for industrial production,and the fabricated electrode has potential application in high-current-density water splitting.展开更多
In an electrocatalyst with a heterointerface structure,the different interfaces can efficiently adjust the catalyst’s conductivity and electron arrangement,thereby enhancing the activity of the electrocatalyst.Ultrat...In an electrocatalyst with a heterointerface structure,the different interfaces can efficiently adjust the catalyst’s conductivity and electron arrangement,thereby enhancing the activity of the electrocatalyst.Ultrathin and smaller Ni Fe LDH was successfully constructed on the surface of SnOnanosheet supported NF by layer by layer assembly,and exhibits lower overpotential of 234 mV at a current density of 10 m A cm,which only increases by 6.4%even at a high current density of 100 mA cm.The excellent OER activity of catalyst is attributed to the contribution of the semiconductor SnOelectron transport layer.Through experiments and characterization,3d structure SnOnanosheets control the growth of ultra-thin nickel-iron,the hierarchical interface between SnOand Ni Fe LDH can change the electron arrangement around the iron and nickel active centers at the interface,resulting the valence states of iron slightly increased and Nicontent increased.The result will promote the oxidation of water.Meanwhile,the SnOsemiconductor as electron transport layer is conducive to trapping electrons generated in oxidation reaction,promoting electrons transferring from the Ni Fe LDH active center to the Ni substrate more quickly,and enhance the activity of Ni Fe LDH.It also shows excellent activity in an electrolyte solution containing 0.5 M methanol and 1 M KOH,and only 1.396 V(vs.RHE)is required to drive a current density of 10 mA cm.展开更多
Introduction of vacancies is a promising route to enhance the performance of electrocatalysts by tuning the electronic structure and bonding energy.Here,the influence of ultrasound treatment on the O vacancies formati...Introduction of vacancies is a promising route to enhance the performance of electrocatalysts by tuning the electronic structure and bonding energy.Here,the influence of ultrasound treatment on the O vacancies formation and interlayer spacing in NiFe layered double hydroxide(LDH)was investigated.It is found that the strong ultrasound treatment results in rich O vacancies on the surface of NiFe LDH,which affect the electrocatalysis performance.Besides,the ultrasound treated NiFe LDH electrocatalysts had a reduced thickness with a hexagonal nanosheet morphology and expanded interlayer distance,which could promote the diffusion of reactant and generated gas.When the obtained defect-rich NiFe LDH electrocatalyst prepared by a 10-min ultrasonic treatment was applied to catalyze oxygen evolution reaction(OER),only 194 mV of overpotential was needed to maintain a current density of 10 mA⋅cm^(-2).展开更多
将甲烷以低能耗的方式直接转化为甲醇等高附加值的化学品一直是可持续化工产业的重要目标和重大挑战.本文制备了三维(3D)ZnO/CdS/NiFe层状双金属氢氧化物(LDH)核/壳/分层纳米线阵列(NWAs)结构材料并将其用于室温、模拟阳光照射下甲烷的...将甲烷以低能耗的方式直接转化为甲醇等高附加值的化学品一直是可持续化工产业的重要目标和重大挑战.本文制备了三维(3D)ZnO/CdS/NiFe层状双金属氢氧化物(LDH)核/壳/分层纳米线阵列(NWAs)结构材料并将其用于室温、模拟阳光照射下甲烷的光电催化氧化.结果表明3D ZnO/CdS/NiFe-LDH具有优异的光电化学性能及催化活性,甲烷气氛下的光电流密度达到了6.57 mA·cm^(−2)(0.9 V vs RHE),其催化甲烷生成甲醇及甲酸产量分别是纯ZnO的5.0和6.3倍,两种主要产物的总法拉第效率达到54.87%.CdS纳米颗粒(NPs)的沉积显著提升了复合物对可见光的吸收,促进了光生载流子的分离.而具有三维多孔结构的NiFe-LDH纳米片的引入改善了甲烷氧化表面反应动力学,起到了优异的助催化作用;并且有效抑制了O_(2)^(•-)的产生,防止O_(2)^(•-)进一步将甲醇及甲酸氧化为CO_(2),提高了甲醇及甲酸的选择性.最后,提出了三维ZnO/CdS/NiFe-LDH复合材料光电催化甲烷转化为甲醇及甲酸的机理,为甲烷低能耗转化为高价值化学品提供了新思路.展开更多
基金National Natural Science Foundation of China,Grant/Award Numbers:51874357,51872333,U20A20123。
文摘The lattice-oxygen-mediated mechanism is considered as a reasonable mechanism for the electrochemical catalytic oxygen evolution reaction(OER)of NiFe layered double hydroxides(LDHs).A NiFe LDH with distinct lattice contraction and microcrystallization was synthesized via a simple one-step method using sodium gluconate.The lattice contraction is attributed to the interaction of carbon in sodium gluconate and iron in NiFe LDH.The NiFe LDH with optimized microcrystallization and lattice contraction shows a low overpotential of 217 mV at a current density of 10 mA cm^(−2) and excellent durability of 20 h at a high current density of 100 mA cm^(−2).The results revealed that a contractive metal–oxygen bond could boost the intrinsic activity of active sites and the microcrystallization promotes an increase in the number of active sites in terms of unit area.The chemical environment of oxygen elemental characterization and resistance at different chronopotentiometry times confirm that the lattice oxygen element is indeed involved in the process of OER,supporting the lattice-oxygen-mediated mechanism of NiFe LDH.Density functional theory calculations reveal that contractive metal–oxygen bonds induced a reduction of the adsorption energy barrier of intermediate products,thus improving the intrinsic catalytic activity.The special characteristics of microcrystallization and lattice contraction of NiFe LDH provide a strategy to improve both the number and the intrinsic activity of active sites in a versatile manner.
文摘Developing effective and practical electrocatalyst under industrial electrolysis conditions is critical for renewable hydrogen production.Herein,we report the self-supporting NiFe LDH-MoS_(x) integrated electrode for water oxidation under normal alkaline test condition(1 M KOH at 25℃)and simulated industrial electrolysis conditions(5 M KOH at 65℃).Such optimized electrode exhibits excellent oxygen evolution reaction(OER)performance with overpotential of 195 and 290 mV at current density of 100 and 400 mA·cm^(-2) under normal alkaline test condition.Notably,only over-potential of 156 and 201 mV were required to achieve the current density of 100 and 400mA·cm^(-2) under simulated industrial electrolysis conditions.No significant degradations were observed after long-term durability tests for both conditions.When using in two-electrode system,the operational voltages of 1.44 and 1.72 V were required to achieve a current density of 10 and 100 mA·cm^(-2) for the overall water splitting test(NiFe LDH-MoS_(x)/INF||20%Pt/C).Additionally,the operational voltage of employing NiFe LDH-MoS_(x)/INF as both cathode and anode merely require 1.52 V at 50mA·cm^(-2) at simulated industrial electrolysis conditions.Notably,a membrane electrode assembly(MEA)for anion exchange membrane water electrolysis(AEMWEs)using NiFe LDH-MoS_(x)/INF as an anode catalyst exhibited an energy conversion efficiency of 71.8%at current density of 400 mA·cm^(-2)in 1 M KOH at 60℃.Further experimental results reveal that sulfurized substrate not only improved the conductivity of NiFe LDH,but also regulated its electronic configurations and atomic composition,leading to the excellent activity.The easy-obtained and cost-effective integrated electrodes are expected to meet the large-scale application of industrial water electrolysis.
基金supported by the National Natural Science Foundation of China(No.22209054)the Natural Science Foundation of Hunan Province(Nos.2023JJ30017 and 2023JJ30030)the Natural Science Foundation of Changsha(No.kq2208223)。
文摘Owing to the significant potential of alkalin seawater electrolysis for converting surplus power into eco friendly hydrogen fuel,we developed bifunctional elec trodes that integrate low-crystalline NiFe LDHs and amorphous NiFe alloy on a Ni foam(NF)substrate to enhance this process.Driven by the battery-like charac teristics of NiFe LDHs,an anti-corrosive and active oute layer of NiFe^(vac)OOH continuously forms over time in th hybrid on the anode for the oxygen evolution reaction(OER),effectively mitigating powder shedding caused by corrosion induced by multiple anions in seawater.Mean while,the strong bond between the hybrid and the NF substrate maintains intact hybrid coatings to ensure a rel atively high overall conductivity of the electrodes,signif icantly reducing the negative effects of structura degradation during the OER and hydrogen evolution reaction(HER),as well as the accumulation of contami nants on the electrode surfaces.In long-term tests,thes bifunctionalhybridelectrodesmaintained stable performance,even at a high current density o500 mA·cm^(-2).The cell voltage increased by only 88 m V over 1000 h to 1.970 V during saline electrolysis and by103 mV over 500 h to 2.062 V during seawater electroly sis.Hence,this study provides valuable insights into efficient and stable seawater electrolysis using NiFe LDHs–NiFe alloy hybrids.
基金supported by the National Natural Science Foundation of China(No.22071069).
文摘Nickel-iron layered double hydroxides(NiFe LDHs)represent a promising candidate for oxygen evolution reaction(OER),however,are still confronted with insufficient activity,due to the slow kinetics of electrooxidation of Ni^(2+)cations for the high-valent active sites.Herein,nanopore-rich NiFe LDH(PR-NiFe LDH)nanosheets were proposed for enhancing the OER activity together with stability.In the designed catalyst,the confined nanopores create abundant unsaturated Ni sites at edges,and decrease the migration distance of protons down to the scale of their mean free path,thus promoting the formation of high-valent Ni^(3+)/^(4+)active sites.The unique configuration further improves the OER stability by releasing the lattice stress and accelerating the neutralization of the local acidity during the phase transformation.Thus,the optimized PR-NiFe LDH catalysts exhibit an ultralow overpotential of 278 mV at 10 mA∙cm^(−2)and a small Tafel slope of 75 mV∙dec^(−1),which are competitive among the advanced LDHs based catalysts.Moreover,the RP-NiFe LDH catalyst was implemented in anion exchange membrane(AEM)water electrolyzer devices and operated steadily at a high catalytic current of 2 A over 80 h.These results demonstrated that PR-NiFe LDH could be a viable candidate for the practical electrolyzer.This concept also provides valuable insights into the design of other catalysts for OER and beyond.
基金financially supported by the Fundamental Research Funds for the Central Universities,JLU(No.45122031B004)。
文摘NiFe layered double hydroxides(NiFe LDHs)have been intensively developed for the oxygen evolution reaction(OER)in alkaline media;however,their unsatisfactory hydrogen evolution reaction(HER)performance limits their practical application in overall water splitting.Herein,a simple and efficient one-step electrodeposition method is used to accomplish in situ growth of NiFe LDHsNiFe alloy gradient hybrid coatings on a carbon cloth(CC).Within the binder-free electrode,NiFe LDHs nanosheets with a low-crystalline nature exhibit highly active bifunctional OER/HER activities,and the NiFe alloy acts as a stable electron highway and strong skeleton bridge between NiFe LDHs and the CC.When the electrodes are simultaneously employed as the cathode and anode for overall water splitting,they require low cell potentials of 1.441 V at10 mA·cm^(-2)and 1.703 V at 100 mA·cm^(-2),respectively,and they demonstrate outstanding stability at a current density greater than 100 mA·cm^(-2)for more than 100 h.This is one of the best bifunctional OER and HER catalysts for overall water splitting.Both lattice defects and surface reconstructions crucially contribute to the bifunctional OER/HER activities of NiFe LDHs.This simple and scalable synthesis approach presents an intriguing paradigm for industrial production,and the fabricated electrode has potential application in high-current-density water splitting.
基金the National Natural Science Foundation of China(No.51778296)。
文摘In an electrocatalyst with a heterointerface structure,the different interfaces can efficiently adjust the catalyst’s conductivity and electron arrangement,thereby enhancing the activity of the electrocatalyst.Ultrathin and smaller Ni Fe LDH was successfully constructed on the surface of SnOnanosheet supported NF by layer by layer assembly,and exhibits lower overpotential of 234 mV at a current density of 10 m A cm,which only increases by 6.4%even at a high current density of 100 mA cm.The excellent OER activity of catalyst is attributed to the contribution of the semiconductor SnOelectron transport layer.Through experiments and characterization,3d structure SnOnanosheets control the growth of ultra-thin nickel-iron,the hierarchical interface between SnOand Ni Fe LDH can change the electron arrangement around the iron and nickel active centers at the interface,resulting the valence states of iron slightly increased and Nicontent increased.The result will promote the oxidation of water.Meanwhile,the SnOsemiconductor as electron transport layer is conducive to trapping electrons generated in oxidation reaction,promoting electrons transferring from the Ni Fe LDH active center to the Ni substrate more quickly,and enhance the activity of Ni Fe LDH.It also shows excellent activity in an electrolyte solution containing 0.5 M methanol and 1 M KOH,and only 1.396 V(vs.RHE)is required to drive a current density of 10 mA cm.
基金financial supports from the Natural Science Foundation of Henan Province(NO.202300410433)the Scientific Research Foundation of Zhengzhou University(32210862,32211241).
文摘Introduction of vacancies is a promising route to enhance the performance of electrocatalysts by tuning the electronic structure and bonding energy.Here,the influence of ultrasound treatment on the O vacancies formation and interlayer spacing in NiFe layered double hydroxide(LDH)was investigated.It is found that the strong ultrasound treatment results in rich O vacancies on the surface of NiFe LDH,which affect the electrocatalysis performance.Besides,the ultrasound treated NiFe LDH electrocatalysts had a reduced thickness with a hexagonal nanosheet morphology and expanded interlayer distance,which could promote the diffusion of reactant and generated gas.When the obtained defect-rich NiFe LDH electrocatalyst prepared by a 10-min ultrasonic treatment was applied to catalyze oxygen evolution reaction(OER),only 194 mV of overpotential was needed to maintain a current density of 10 mA⋅cm^(-2).
文摘将甲烷以低能耗的方式直接转化为甲醇等高附加值的化学品一直是可持续化工产业的重要目标和重大挑战.本文制备了三维(3D)ZnO/CdS/NiFe层状双金属氢氧化物(LDH)核/壳/分层纳米线阵列(NWAs)结构材料并将其用于室温、模拟阳光照射下甲烷的光电催化氧化.结果表明3D ZnO/CdS/NiFe-LDH具有优异的光电化学性能及催化活性,甲烷气氛下的光电流密度达到了6.57 mA·cm^(−2)(0.9 V vs RHE),其催化甲烷生成甲醇及甲酸产量分别是纯ZnO的5.0和6.3倍,两种主要产物的总法拉第效率达到54.87%.CdS纳米颗粒(NPs)的沉积显著提升了复合物对可见光的吸收,促进了光生载流子的分离.而具有三维多孔结构的NiFe-LDH纳米片的引入改善了甲烷氧化表面反应动力学,起到了优异的助催化作用;并且有效抑制了O_(2)^(•-)的产生,防止O_(2)^(•-)进一步将甲醇及甲酸氧化为CO_(2),提高了甲醇及甲酸的选择性.最后,提出了三维ZnO/CdS/NiFe-LDH复合材料光电催化甲烷转化为甲醇及甲酸的机理,为甲烷低能耗转化为高价值化学品提供了新思路.
