Unconventional grain fragmentation creates high-density boundaries for efficient CO2-to-C2+ electro-conversion at ampere-level current density

Abstract

Electrocatalytic CO₂ reduction reaction (CO₂RR) to produce multi-carbon products (C₂₊) is one of the most sustainable manners to achieve net-zero carbon emissions. Among many approaches, enriching grain boundaries (GBs) in copper (Cu) catalysts has been demonstrated to enable enhancement for C₂₊ production. However, it still lacks effective strategies to controllably synthesize abundant GBs, rendering efficient C₂₊ production a persistent challenge, especially at ampere-level current density. Herein, we propose a novel strategy, which can achieve unconventional grain fragmentation during thermal annealing and thus create controllable GB densities. The catalyst with the utmost GB density exhibits a peak C₂₊ faradaic efficiency of ca. 70.0 % in H-type cell and 68.2 % in flow cell; even more impressively, it delivers an ultra-high C₂₊ current density of 0.768 A cm⁻², outperforming most recently reported results. A combination of in situ spectroscopies and theoretical calculations reveal that the enrichment of GBs yields more active sites for a higher *CO coverage, leading to promotion of the *CO-*CO coupling process and ultimately high C₂₊ production performance.