Design of reaction-driven active configuration for enhanced CO2 electroreduction

Abstract

Metal-nitrogen-carbon single-atom catalysts (SACs) have emerged as promising candidates for electrocatalytic CO₂ reduction reaction. However, the perpendicular $d_{z^2}$ orbital within planar metal site mainly interacts with *COOH, resulting in inferior CO₂ activation. Inspired by reaction-driven active configuration, here we propose to upshift nickel single-atom away from nitrogen-carbon substrate, prominently promoting the interaction between CO₂ and other d orbitals besides $d_{z^2}$. Theoretical and experimental analyses reveal that upshifting nickel site away substrate induces $d_{\mathrm{xz}}$, $d_{\mathrm{yz}}$, and $d_{z^2}$ to hybridize with CO₂, expediting CO₂ conversion to *COOH. The planar and out-of-plane Ni-N sites are formed on carbon nanosheet (Ni₁-N/C_NS) and curved nanoparticle (Ni₁-N/C_NP), respectively, which is verified by X-ray absorption fine structure spectroscopy. Impressively, the Ni₁-N/C_NP presents CO Faradaic efficiency of 96.4 % at 500 mA cm⁻² and energy conversion efficiency of 79.8 % in flow cell, outperforming Ni₁-N/C_NS and most SACs. This work highlights the simulation of reaction-driven active sites for efficient electrocatalysis.