摘要
迟缓的水解离动力学严重限制了碱性电催化析氢反应的速率.寻找高活性电催化剂,并阐明水的解离机制具有挑战性和必要性.本文通过对Ni_(45)Zr_(35)Ti_(20)金属玻璃前驱体进行表面脱合金处理,制备了一体式纳米多孔镍(nanoporous nickel,np-Ni)电极.在1 mol L^(-1)KOH溶液中,该np-Ni电极在10 mA cm^(-2)电流密度下显示出20 mV的析氢过电位和快速的水解离动力学.优异的性能不仅源于三维互连的导电网络提供的大表面积,还源于其独特的表面性质带来的本征催化活性的增强.进一步研究表明,镍表面天然形成的氧组分类型对水分子的解离有重要影响.特别是,当晶格氧原子几乎消失时,镍表面以吸附氧原子终止,并表现出最快的水离解动力学.密度泛函理论计算表明,吸附氧原子作为镍金属的表面终止时,附近的极性H_(2)O分子的取向和构型会受到吸附氧的强烈影响.最终,界面水分子的H-OH键可以以类似于氢键的方式被有效激活.这项工作不仅提供了一种高性能/低成本的电催化剂,而且深入研究了水解离的化学过程,有利于电催化剂的合理设计.
Sluggish water dissociation kinetics severely limits the rate of alkaline electrocatalytic hydrogen evolution reaction(HER).Therefore,finding highly active electrocatalysts and clarifying the mechanism of water dissociation are challenging but important.In this study,we report an integrated nanoporous nickel(np-Ni)catalyst with high alkaline HER performance and the origin of the corresponding enhanced catalytic activity.In 1 mol L^(-1) KOH solution,this np-Ni electrode shows an HER overpotential of 20 mV at 10 mA cm^(-2),along with fast water dissociation kinetics.The excellent performance is not only attributed to the large surface area provided by the three-dimensional interconnected conductive network but also from the enhanced intrinsic activity induced by the unique surface properties.Further studies reveal that the types of oxygen species that naturally form on the Ni surface play a key role in water dissociation.Remarkably,when the lattice oxygen almost disappears,the Ni surface terminates with_(ads)orbed oxygen(O_(ads)),exhibiting the fastest water dissociation kinetics.Density functional theory calculation suggests that when O_(ads)acts as the surface termination of Ni metal,the orientation and configuration of polar water molecules are strongly affected by O_(ads).Finally,the H–OH bond of interfacial water molecules is effectively activated in a manner similar to hydrogen bonding.This work not only identifies a high-performance and low-cost electrocatalyst but also provides new insights into the chemical processes underlying water dissociation,thus benefiting the rational design of electrocatalysts.
作者
胡庆丰
陈泽霖
王嘉骏
郑学荣
韩晓鹏
邓意达
胡文彬
Qingfeng Hu;Zelin Chen;Jiajun Wang;Xuerong Zheng;Xiaopeng Han;Yida Deng;Wenbin Hu(School of Materials Science and Engineering,Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education,Tianjin University,Tianjin 300072,China;State Key Laboratory of Marine Resource Utilization in South China Sea,School of Materials Science and Engineering,Hainan University,Haikou 570228,China;Joint School of National University of Singapore and Tianjin University,International Campus of Tianjin University,Binhai New City,Fuzhou 350207,China)
基金
supported by the National Natural Science Foundation of China(51571151,51701139,51671143,52177220,and 51804216)。
