Subsurface engineering for directional-selective CO₂-to-ethanol electrocatalysis at industrial-level.

Abstract

The challenge in precisely controlling the adsorption configuration of oxygen-binding intermediates in the branching path following C-C coupling constrains the directed selectivity of electroreduction CO₂-to-ethanol. Here, we present a subsurface Co-doped CuS (Co-Sub-CuS) catalyst, which exhibits directed selectivity toward ethanol. We elucidate the role of subsurface doping in enhancing the oxophilicity of surface Cu sites, thereby facilitating the conversion of key intermediates (^*CHCHO^*) via the formation of surface-O bonds, guiding subsequent protonation towards ethanol. Moreover, the surface sulfur vacancies created by subsurface Co-doping help regulate the optimal distance between dual sites, facilitating asymmetric C-C coupling. Theoretical calculations combined with in-situ isotopic spectroscopy validate these views, and the branching pathway for converting ^*CHCO to ^*CHCHO^* is captured. Consequently, in a membrane electrode assembly electrolyzer, the optimized Co-Sub-CuS achieves an ethanol Faradaic efficiency of 78.7% at a partial current density of 550.9 mA cm^-2, with stability over 305 h at industrial-level current density of 700 mA cm^-2. These findings provide a rational design for the development of directionally selective catalysts for CO₂ electroreduction.