High-throughput CO-to-acetate electroconversion using current-dependent reconstructed Cu grain boundaries†

Electrochemical CO reduction (COR) offers a sustainable route for the highly selective production of high-value multi-carbon products at low current densities. However, achieving industrial-scale production remains challenging, as reconciling high current densities (>1 A cm⁻²) with product selectivity has yet to be realized. The realization of COR at ampere-level currents for acetic acid production remains hindered by the insufficient availability of highly active sites needed to facilitate CO coupling under high-flux conditions. Here, we developed a copper oxybromide catalyst that in situ generates a high density of grain boundaries (GBs) during COR, as evidenced by high-resolution TEM. Density functional theory calculations verified the high activities of GB-rich surfaces due to stronger *CO adsorption compared to flat Cu(111). Coupled with pressurized CO (10 atm), these rich GBs can effectively adsorb CO and promote this coupling, further leading to a record acetic acid partial current density of 2 A cm⁻² (67% faradaic efficiency at 3 A cm⁻² total current), outperforming the state-of-the-art Cu-based catalysts. This work introduces an effective catalyst for enabling industrial-scale COR, highlighting the critical role of structural design in achieving high-performance electrochemical conversion.