Limited by the sluggish kinetics at the cathode of proton exchange membrane fuel cells(PEMFCs),optimizing platinum-based alloy catalysts for oxygen reduction reaction remains a key target toward industrialization.Stra...Limited by the sluggish kinetics at the cathode of proton exchange membrane fuel cells(PEMFCs),optimizing platinum-based alloy catalysts for oxygen reduction reaction remains a key target toward industrialization.Strain engineering is widely employed to tune Pt-M catalysts,but its impact on the structure-property relationship is often interwoven with multiple factors.In this work,we propose a bi-stage strain tuning method and demonstrate it on the most common PtCo catalysts.Macro-strain is introduced by synthesizing single-crystal PtCo nanodendrites,whereas mild acid etching introduces micro-strain to the surface.The half-wave potential of as-treated catalysts reaches 0.959 V,and mass activity is up to 0.69 A mg^(−1)_(Pt).A minimal decrease of 2 mV is observed for half-wave potential after 10,000 cycles.Detailed analysis using advanced transmission electron microscopy,wide-angle X-ray scattering,etc.provides direct evidence that surface disorder at the atomic scale accounts for the enhanced activity and stability.In contrast,the simplicity of this approach allows for scaling up on Pt-M catalysts,as demonstrated on PEMFCs.The bi-stage strain tuning strategy provides a new perspective and reference for improving the activity and durability of Pt-M catalysts.展开更多
The recent report of superconductivity in nitrogen-doped lutetium hydride(Lu-H-N)at 294 K and 1 GPa brought hope for long-sought-after ambient-condition superconductors.However,the failure of scientists worldwide to i...The recent report of superconductivity in nitrogen-doped lutetium hydride(Lu-H-N)at 294 K and 1 GPa brought hope for long-sought-after ambient-condition superconductors.However,the failure of scientists worldwide to independently reproduce these results has cast intense skepticism on this exciting claim.In this work,using a reliable experimental protocol,we synthesized Lu-H-N while minimizing extrinsic influences and reproduced the sudden change in resistance near room temperature.With quantitative comparison of the temperaturedependent resistance between Lu-H-N and the pure lutetium before reaction,we were able to clarify that the drastic resistance change is most likely caused by a metal-to-poor-conductor transition rather than by superconductivity.Herein,we also briefly discuss other issues recently raised in relation to the Lu-H-N system.展开更多
基金the National Natural Science Foundation of China(NO.12274010,12474003)Beijing Nova Program(20240484584)+2 种基金the support from the Shanghai Key Laboratory of Material Frontiers Research in Extreme Environments,China(No.22dz2260800)the Shanghai Science and Technology Committee,China(No.22JC1410300)the National Natural Science Foundation of China(No.52103330)。
文摘Limited by the sluggish kinetics at the cathode of proton exchange membrane fuel cells(PEMFCs),optimizing platinum-based alloy catalysts for oxygen reduction reaction remains a key target toward industrialization.Strain engineering is widely employed to tune Pt-M catalysts,but its impact on the structure-property relationship is often interwoven with multiple factors.In this work,we propose a bi-stage strain tuning method and demonstrate it on the most common PtCo catalysts.Macro-strain is introduced by synthesizing single-crystal PtCo nanodendrites,whereas mild acid etching introduces micro-strain to the surface.The half-wave potential of as-treated catalysts reaches 0.959 V,and mass activity is up to 0.69 A mg^(−1)_(Pt).A minimal decrease of 2 mV is observed for half-wave potential after 10,000 cycles.Detailed analysis using advanced transmission electron microscopy,wide-angle X-ray scattering,etc.provides direct evidence that surface disorder at the atomic scale accounts for the enhanced activity and stability.In contrast,the simplicity of this approach allows for scaling up on Pt-M catalysts,as demonstrated on PEMFCs.The bi-stage strain tuning strategy provides a new perspective and reference for improving the activity and durability of Pt-M catalysts.
文摘The recent report of superconductivity in nitrogen-doped lutetium hydride(Lu-H-N)at 294 K and 1 GPa brought hope for long-sought-after ambient-condition superconductors.However,the failure of scientists worldwide to independently reproduce these results has cast intense skepticism on this exciting claim.In this work,using a reliable experimental protocol,we synthesized Lu-H-N while minimizing extrinsic influences and reproduced the sudden change in resistance near room temperature.With quantitative comparison of the temperaturedependent resistance between Lu-H-N and the pure lutetium before reaction,we were able to clarify that the drastic resistance change is most likely caused by a metal-to-poor-conductor transition rather than by superconductivity.Herein,we also briefly discuss other issues recently raised in relation to the Lu-H-N system.
