Dual active sites-dependent syngas proportions from aqueous CO2 electroreduction

Abstract

Electroreduction of aqueous CO2 is a sustainable approach to produce tunable syngas, which demands the rational design of dual-active-sites catalysts for individual CO2 reduction reaction (CRR) and hydrogen evolution reaction (HER). Here, the self-supporting nickel@nitrogen-doped carbon nanotubes grown on carbon nanofiber (Ni@NCNTs-CNF) is developed with Ni single atoms (SAs) and nanoparticles (NPs) functioning as CRR and HER sites respectively. Benefiting from the hierarchical nanostructures for effective electron transport and mass diffusion, as well as the high accessibility of dual-active sites, Ni@NCNTs-CNF catalysts can mediate aqueous CO2 into CO/H2 (2:1) with a 100 % Faraday efficiency and a high current density (25 mA cm−2) at low working potential (-0.8 V). By manipulating the Ni SAs/Ni NPs ratio, the CO/H2 proportion is easily modulated in a wide range from 1:4 to 5:1, independence of the working potential (-0.6 to -0.8 V). Our findings provide fresh insights into the design of dual-active-sites catalysts.