A robust Ni single-atom catalyst for industrial current and exceptional selectivity in electrochemical CO2 reduction to CO

Abstract

While achieving a faradaic efficiency (FE) over 90% in the electroreduction of CO₂ to CO with a single transition metal atom anchoring nitrogen-doped carbon (M–N–C) catalyst is indeed notable, the challenge remains in elevating the CO current density to a level suitable for industrial application. Here, we present the synthesis of a hydrophobic Ni single-atom catalyst (Ni–N-HCNs-5h) featuring unsaturated Ni–N coordination and abundant micropores, created by immobilizing nickel atoms on hollow carbon nanospheres. In virtue of the increased accumulation of CO₂, inhibited hydrogen evolution reaction (HER), and optimized adsorption strength of intermediates, the Ni–N-HCNs-5h achieves an exceptional CO current density of 577 mA cm⁻² with 96% CO FE at a potential of −1.17 V vs. RHE. Impressively, CO FE over 95% is sustained across a wide range of total current densities, spanning from 100 to 600 mA cm⁻². Density functional theory calculations provide insights into reducing the free energy for generating the *COOH intermediate and the suppression of the HER on unsaturated NiN₃V sites (where V denotes a coordination vacancy) compared to the NiN₄ site. Our work sheds new light on developing M–N–C catalysts with high product selectivity and current densities suitable for industrial-scale CO₂ electroreduction to CO.