Electrochemical CO2 reduction: Progress and opportunity with alloying copper

Electroreduction of carbon dioxide (CO₂) into value-added chemicals offers an entrancing approach to maintaining the global carbon cycle and eliminating environmental threats. A key obstacle to achieving long-term and large-scale implementation of electrochemical CO₂ reduction technology is the lack of active and selective catalysts. Copper (Cu) is one of the few candidates that can facilitate C–C coupling to obtain high-energy oxygenates and hydrocarbons beyond carbon monoxide (CO), but it suffers from poor selectivity for products of interest and high overpotentials. Alloying is an effective way to break the linear scaling relations and uniquely manipulate the reactivity and selectivity, which is hard to achieve by using monometallic compositions alone. By alloying Cu with other metals, one could change the catalytic properties of the catalyst by tuning the local electronic structure and modulating the adsorption strength of the reaction intermediates, thus improving the catalytic activity and selectivity. In this review, we focus on the recently developed Cu-based alloy catalysts (including conventional alloys, high-entropy alloys and single-atom alloys) that have been applied in electrocatalytic CO₂ reduction (ECR). Theoretical calculations and experimental advances in understanding the key rate-limiting and selectivity-determining steps in those alloys are summarized, with a particular focus on identifying binding energy descriptors and the dynamic product formation mechanisms. In addition, we outline the opportunities and challenges in the fundamental understanding of ECR by recommending advanced in-situ characterization techniques and standardized electrochemical methods and offer atomic-level design principles for steering the reaction pathways to the desired products.