Current strategies to enhance Zn reversibility in aqueous Zn batteries(AZBs)primarily focus on inducing planar deposition.However,electrodissolution,as the initial operational step in AZBs,significantly affects deposi...Current strategies to enhance Zn reversibility in aqueous Zn batteries(AZBs)primarily focus on inducing planar deposition.However,electrodissolution,as the initial operational step in AZBs,significantly affects deposition behavior and reversibility,yet it is surprisingly overlooked.Herein,the crucial electrodissolution behavior of Zn electrodes and its impact on irreversibility are comprehensively elucidated.First,the dissolution pathways at different current densities are investigated at the microscopic level.As the current density increases,the electrodissolution behavior evolves from“point dissolution”to“line dissolution”and ultimately to“surface dissolution”.Meanwhile,the proportion of dissolution area and depth changes at different operating protocols are quantitatively analyzed.Then,Combining theoretical calculations and experimental tests,dissolution differences among various crystal planes are unveiled with the sequence from weakest to toughest being(110),(101),(103),(102),(100),and(002).Additionally,morphological characterization and electrochemical-mass transport coupling models demonstrate that dissolution reshapes the surface morphology and interfacial microenvironment for deposition,which in turn determines nucleation and growth sites.More importantly,the mechanism of“dead Zn”formation is clarified by considering the internal structural heterogeneity of the dendrites and the external concentration distribution.As a proof of concept,Zn electrodes with preferred orientations constructed via epitaxial growth demonstrated uniform dissolution and achieved over a 46%improvement in cycling lifespan compared to Zn electrodes with random orientations.This work provides a profound comprehension of the largely overlooked electrodissolution,opening a novel avenue for improving the reversibility of metal electrodes.展开更多
Carbon-supported platinum nanoparticles(Pt/C)are widely used electrocatalysts in proton exchange membrane fuel cell and electrolyzer applications and represent a substantial part of the capital expenditure of these de...Carbon-supported platinum nanoparticles(Pt/C)are widely used electrocatalysts in proton exchange membrane fuel cell and electrolyzer applications and represent a substantial part of the capital expenditure of these devices.Platinum being a critical raw material,its recovery is critical for the deployment of these technologies.In this contribution,the first step of a recycling protocol,i.e.the leaching of Pt/C,is studied.To avoid the use of concentrated acids and oxidants,the focus of the present study is on the design of an efficient electrochemical protocol.In particular,the values of the upper and lower potential limits have an impact on Pt dissolution efficiency.The upper potential limit should avoid(or at least limit)Pt particles'detachment from the carbon support and the lower potential limit should take into account the competition between the platinum dissolution and the unwanted platinum redeposition.The evolution of the particle morphology and dissolution rate were monitored by coupling a statistical analysis of TEM images and ICP-MS concentration measurements.The cycling potential window was first optimized for a model commercial Pt/C catalyst in a low-chloride concentration electrolyte,leading to a full Pt leaching efficiency(99%).A similar protocol was transferred to more technological objects:MEA aged under realistic conditions.The MEAs were electrochemically treated without any prior GDL separation and the efficiency of the process was demonstrated.展开更多
基金support from the National Natural Science Foundation of China(523B2061)National Innovative Talents Program(GG2090007001)University of Science and Technology of China Startup Program(KY2090000044).
文摘Current strategies to enhance Zn reversibility in aqueous Zn batteries(AZBs)primarily focus on inducing planar deposition.However,electrodissolution,as the initial operational step in AZBs,significantly affects deposition behavior and reversibility,yet it is surprisingly overlooked.Herein,the crucial electrodissolution behavior of Zn electrodes and its impact on irreversibility are comprehensively elucidated.First,the dissolution pathways at different current densities are investigated at the microscopic level.As the current density increases,the electrodissolution behavior evolves from“point dissolution”to“line dissolution”and ultimately to“surface dissolution”.Meanwhile,the proportion of dissolution area and depth changes at different operating protocols are quantitatively analyzed.Then,Combining theoretical calculations and experimental tests,dissolution differences among various crystal planes are unveiled with the sequence from weakest to toughest being(110),(101),(103),(102),(100),and(002).Additionally,morphological characterization and electrochemical-mass transport coupling models demonstrate that dissolution reshapes the surface morphology and interfacial microenvironment for deposition,which in turn determines nucleation and growth sites.More importantly,the mechanism of“dead Zn”formation is clarified by considering the internal structural heterogeneity of the dendrites and the external concentration distribution.As a proof of concept,Zn electrodes with preferred orientations constructed via epitaxial growth demonstrated uniform dissolution and achieved over a 46%improvement in cycling lifespan compared to Zn electrodes with random orientations.This work provides a profound comprehension of the largely overlooked electrodissolution,opening a novel avenue for improving the reversibility of metal electrodes.
文摘Carbon-supported platinum nanoparticles(Pt/C)are widely used electrocatalysts in proton exchange membrane fuel cell and electrolyzer applications and represent a substantial part of the capital expenditure of these devices.Platinum being a critical raw material,its recovery is critical for the deployment of these technologies.In this contribution,the first step of a recycling protocol,i.e.the leaching of Pt/C,is studied.To avoid the use of concentrated acids and oxidants,the focus of the present study is on the design of an efficient electrochemical protocol.In particular,the values of the upper and lower potential limits have an impact on Pt dissolution efficiency.The upper potential limit should avoid(or at least limit)Pt particles'detachment from the carbon support and the lower potential limit should take into account the competition between the platinum dissolution and the unwanted platinum redeposition.The evolution of the particle morphology and dissolution rate were monitored by coupling a statistical analysis of TEM images and ICP-MS concentration measurements.The cycling potential window was first optimized for a model commercial Pt/C catalyst in a low-chloride concentration electrolyte,leading to a full Pt leaching efficiency(99%).A similar protocol was transferred to more technological objects:MEA aged under realistic conditions.The MEAs were electrochemically treated without any prior GDL separation and the efficiency of the process was demonstrated.
