Cu vacancies in in-situ reconstructed CuxSe catalysts enhancing C2+ production in CO2 electroreduction

Copper (Cu)-based catalysts have demonstrated promising selectivity and activity in electroreducing CO 2 to multi-carbon (C 2+ ) products. Among them, oxide-derived Cu catalysts exhibit high selectivity for C 2+ products in the CO 2 electroreduction reaction (CO 2 RR). Cu chalcogenide-derived catalysts offer a promising approach to tune the electronic structure of Cu sites via surface reconstruction, thereby affecting the product distribution. However, the effect of in-situ anion dissolution, especially Se ions, on the electronic structure of Cu selenides at negative potentials remains overlooked, despite its potential to significantly affect catalytic activity. In this study, we developed a series of Cu selenide catalysts with varying Cu/Se ratios to optimize electronic structures and enhance CO 2 RR performance. Among them, Cu 1.8 Se, featuring Cu vacancies, exhibited the highest activity for C 2+ products formation and the highest C 2+ /C 1 products ratio, nearly 2–3 times greater than the others. This catalyst also demonstrated good stability over 38 h of electrolysis under −450 mA cm −2 , with a maximum C 2+ products Faradaic efficiency (FE) of up to 70 %. In-situ surface reconstruction analysis revealed Se loss and Cu + /Cu 2+ reduction of the initial Cu 1.8 Se catalyst, forming Cu/Cu x Se structures with Cu vacancies, identified as the real active sites. Density functional theory (DFT) calculations and in-situ infrared absorption spectroscopy confirmed that Cu vacancies play a critical role in stabilizing *CHOCO intermediates for C–C coupling while suppressing hydrogen evolution reaction and C 1 products formation. These findings highlight Cu vacancy engineering as an effective strategy for enhancing C 2+ selectivity in CO 2 RR.