摘要
Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily accessible active sites for CO_(2) electroreduction remains challenging yet indispensable.In this work,a reliable poly(ethyleneimine)(PEI)-assisted strategy is developed to prepare a hollow carbon nanocomposite comprising a single-site Ni-modified carbon shell and confined Ni nanoparticles(NPs)(denoted as Ni@NHCS),where PEI not only functions as a mediator to induce the highly dispersed growth of Ni NPs within hollow carbon spheres,but also as a nitrogen precursor to construct highly active atomically-dispersed Ni-Nx sites.Benefiting from the unique structural properties of Ni@NHCS,the aggregation and exposure of Ni NPs can be effectively prevented,while the accessibility of abundant catalytically active Ni-Nx sites can be ensured.As a result,Ni@NHCS exhibits a high CO partial current density of 26.9 mA cm^(-2) and a Faradaic efficiency of 93.0% at-1.0 V vs.RHE,outperforming those of its PEI-free analog.Apart from the excellent activity and selectivity,the shell confinement effect of the hollow carbon sphere endows this catalyst with long-term stability.The findings here are anticipated to help understand the structure-activity relationship in Ni-based carbon catalyst systems for electrocatalytic CO_(2) reduction.Furthermore,the PEI-assisted synthetic concept is potentially applicable to the preparation of high-performance metal-based nanoconfined materials tailored for diverse energy conversion applications and beyond.
电化学CO_(2)还原生产高附加值化学品和燃料是能源转换领域的研究热点之一.开发具有高导电性和高暴露活性位点的高效催化剂用于CO_(2)电还原仍然具有挑战性.本文开发了一种可靠的聚乙烯亚胺(PEI)辅助策略用于制备中空碳纳米复合材料,该纳米复合材料包含单位点Ni修饰的碳壳和受限的Ni纳米颗粒(简写为Ni@NHCS),其中PEI不仅可以作为媒介诱导Ni纳米颗粒在空心碳球内高度分散地生长,而且还能提供氮源构建高分散的Ni-N_x活性位点.Ni@NHCS的独特结构,既可以有效防止Ni纳米颗粒的团聚和暴露,同时又可以确保大量Ni-N_x活性位点的可及性.因此,Ni@NHCS在-1.0 V vs.RHE的工作电位下,可实现高CO分电流密度(26.9 mA cm^(-2))和高CO法拉第效率(93.0%),显著优于无PEI的对照样品.除了具有较好的活性和选择性,得益于中空碳球的壳层限域效应,该材料还具有出色的稳定性.本研究有望帮助理解电催化CO_(2)还原中镍基碳催化剂体系的构效关系.此外,本工作报道的PEI辅助合成概念还适用于开发其他高性能、多用途的金属基纳米限域材料.
