Regulating surface In–O in In@InO_(x) core‐shell nanoparticles for boosting electrocatalytic CO_(2) reduction to formate

调节In@InO_(x)核壳纳米颗粒中的表面In‒O提升电催化还原CO_(2)为甲酸盐性能

To solve the excessive emission of CO_(2) caused by the excessive use of fossil fuels and the corre‐sponding environmental problems,such as the greenhouse effect and climate warming,electrocat‐alytic CO_(2) reduction to liquid fuel with high selectivity is of huge significance for energy conversion and storge.Indium has been considered as a promising and attractive metal for the reduction of CO_(2) to formate.However,the current issues,such as low selectivity and current activity,largely limit the industrial application for electrocatalytic CO_(2) reduction,the design optimization of the catalyst structure and composition is extremely important.Herein,we develop a facile strategy to regulate surface In–O of In@InO_(x) core‐shell nanoparticles and explore the structure‐performance relation‐ship for efficient CO_(2)‐to‐formate conversion though air calcination and subsequent in situ electro‐chemical reconstruction,discovering that the surface In–O is beneficial to stabilize the CO_(2) interme‐diate and generate formate.The optimized AC‐In@InO_(x)‐CNT catalyst exhibits a C1 selectivity up to 98%and a formate selectivity of 94%as well as a high partial formate current density of 32.6 mA cm^(-2).Furthermore,the catalyst presents an excellent stability for over 25 h with a limited activity decay,outperforming the previously reported In‐based catalysts.These insights may open up op‐portunities for exploiting new efficient catalysts by manipulating their surface.

通过可再生能源驱动的电催化二氧化碳还原反应可以将温室气体转化为燃料或有价值的化学品,从而缓解因化石燃料过度消耗而导致的能源短缺和温室效应.在电化学CO_(2)还原(CO_(2)RR)反应获得的产物中,甲酸盐因出色的载氢能力和可在化学工业中用作有机合成原料而被认为是一种具有经济价值和吸引力的产物.然而,CO_(2)RR的高动力学势垒和严重的析氢反应限制了其有效生成,这使构建高效的催化生成甲酸盐的催化剂成为一个巨大挑战.近期,研究者设计了基于过渡金属(如In,Bi和Sn)的催化剂,其对甲酸盐具有较高的选择性.通过金属氧化物(M–O)结构形成的氧化态p-block金属中心可以加快*OCO^(•−)的生成,这通常被认为是生成甲酸盐的关键中间体.此外,很多研究已经报道了M–O结构在催化过程中的重要作用,表面M–O结构可以稳定CO_(2)中间体并促进反应动力学.当通过刻蚀或其他特殊预处理破坏M–O结构时,甲酸盐的形成受到极大阻碍.In具有低毒、高耐腐蚀性和导电性的特点,在开发用于CO_(2)RR生成甲酸的催化剂方面具有巨大潜力.Bocarsly课题组曾经报道,In电极上的甲酸盐选择性很大程度上取决于不同的预处理方法.去除氧化层后的蚀刻电极表现出较低的甲酸盐选择性,而含有氧化层的阳极氧化电极显著提高了甲酸盐的选择性.尽管很多研究报道了In–O物种在催化过程中的重要作用,但关于如何在In基催化剂表面上富集In–O物种的研究很少.本文采用简便的空气煅烧法调节CNT负载的In_(2)O_(3)纳米粒子(NPs)上的In–O含量,以形成AC-In_(2)O_(3)-CNT结构.在经过原位电化学重构过程后,形成了表面富集In–O的核壳结构AC-In@InO_(x)-CNT催化剂,所得的未经煅烧In@InO_(x)-CNT与经过煅烧AC-In@InO_(x)-CNT具有相似的核壳结构.高分辨透射电子显微镜和X射线能谱(EDS)分析结果表明,In为核,非晶InO_(x)为壳.X射线光电子能谱和EDS结果表明,与未经煅烧的In@InO_(x)-CNT相比,AC-In@InO_(x)-CNT中In–O含量更丰富.与In@InO_(x)-CNT催化剂相比,富含In–O的AC-In@InO_(x)-CNT催化剂表现出显著提高的CO_(2)RR活性,其催化生成对甲酸盐的最高法拉第效率(FE)可达到94±1%,在–1.00 V(相比于RHE)时,甲酸盐的部分电流密度可达到32.6 mA cm^(-2),而竞争性的析氢反应几乎可以忽略不计(FE小于2%).经过25 h的稳定性实验,未观察到反应性能下降及催化剂形貌变化,表明AC-In@InO_(x)-CNT催化剂具有较好的稳定性.综上,本文通过构建丰富且稳定的表面M–O结构,为设计高效电催化剂提供新思路.