A vapor-deposited nanotwinned copper thin film enhances C₂ production in CO₂ electroreduction

This work reports vapor-deposited copper thin-film electrocatalysts with tunable twin boundary densities. A prolonged annealing process can promote grain growth and the formation of high-density twin structures. These Cu catalysts with a high twin boundary density exhibit largely enhanced selectivity toward C₂ products, while suppressing the competing hydrogen evolution reaction. Notably, the Cu catalyst annealed for 90 minutes shows a markedly increased C₂/CO ratio compared to less annealed counterparts. In situ TEM investigation captures this dynamic formation of twin boundaries during annealing. These results establish twin boundary engineering as an effective strategy for regulating local reaction environments to promote C-C coupling during CO₂ electroreduction.