化学功能化增强贵金属纳米晶电催化性能

Chemical functionalized noble metal nanocrystals for electrocatalysis

基于电催化过程的可再生和清洁能源的生产、转换和储存技术(如水电解和燃料电池)是缓解全球能源短缺和环境污染问题的有效手段.目前,水电解和燃料电池技术的实际应用缺乏高效、稳定的电催化剂来驱动动力学迟缓的阴极和阳极反应.贵金属纳米晶由于其独特的电子结构和高化学惰性而具有高电催化活性和稳定性.为了提升贵金属纳米晶的本征电催化性能,大量研究聚焦在利用面积效应、晶面效应和不同组分之间的协同效应来调控贵金属的粒径、形貌和化学成分.事实上,贵金属纳米晶的电催化性能也与其表/界面性质密切相关.电催化剂表面的化学功能化可以改变电极/电解质界面结构,从而提高电催化活性和选择性,这对开发新型高效的电催化剂具有重要的理论意义.本文系统介绍了本课题组开发的聚胺(PAM)功能化贵金属纳米电催化剂的合成方法及其在燃料电池和电解池等能源转换装置中的应用,具体包括:通过引入PAM控制反应动力学来调控纳米晶体的结构和形态,构建界面功能化贵金属纳米电催化剂;利用金属表面修饰的PAM分子改变表面催化位点的电子结构、配位环境等物理化学性质来控制反应物和中间体等的吸附行为,从而达到调节催化活性的目的;采用PAM分子来隔离特定活性位点,形成空间位阻,改变金属表面位点的可及性,影响催化反应中反应物的吸附,从而实现对目标反应的选择性.从优化催化性能和通过电催化过程实现高效能量转换的角度,本文列举了PAM功能化催化剂在氧还原反应、析氢反应、甲酸氧化反应和硝酸盐还原反应等重要反应中的最新研究进展;总结了化学功能化贵金属电催化剂的研究进展、当前不足,提出了挑战和未来前景.综上,本文旨在激发对表面/界面功能化及其催化行为的深入研究,从而推进未来与电催化技术相关的可再生能源的生产和环境保护.

Electrocatalysis is an interface-dominated process,in which the activity of the catalyst highly relates to the adsorption/desorption behaviors of the reactants/intermediates/products on the active sites.From the perspective of catalyst design,the chemical functionalization design on noble metal surfaces will inevitably affect the reaction process,which is considered to be one of the effective strategies to tune the electrocatalytic performance of noble metal nanocrystals.Polyamines(PAM)with high stability and good coordination ability have been widely studied as important functional molecules.In this account,we first introduce the PAM-assisted synthesis mechanism of noble metal nanocrystals,which provides a theoretical basis and guidance for their design and optimization with controllable morphology.Then,the effects of adsorbed PAM on the electronic structure,geometric structure,electrode/electrolyte interface structure and catalytic reaction pathway of noble metal-based catalysts are specifically described.The internal mechanism of noble metal-PAM interfacial effect increasing catalyst activity and selectivity is stated,and the latest research progress of PAM functionalized catalysts applied in important reactions is listed,such as hydrogen evolution reaction,oxygen reduction reaction,formic acid oxidation reaction,and nitrate reduction reaction,and so on.These findings open a new avenue for constructing advanced electrocatalysts based on inorganic/organic polymer-mediated interface engineering in various energy-related catalysis/electrocatalysis fields.Finally,the current challenges and future prospects of PAM molecule functionalized noble metal electrocatalysts are proposed.