Maximizing the Formate Formation of CO2 Electroreduction Via Boosting Charge Transfer Ability

The electrochemical reduction reaction of CO2 (CO2RR) is an attractive strategy for achieving carbon-neutral sustainability while the highly active and selective reaction for formate formation remains challenging. In addition, the thermodynamic inertness of CO2 usually leads to a high energy barrier for CO2RR, resulting in a preference for the competitive hydrogen evolution reaction. It is known that CO2RR is a proton-coupled electron transfer (PCET) process and the complicated multi-electron transfer steps occur on the catalyst surface. Therefore, improving the charge transfer ability is considered as an effective approach to maximizing the electrocatalytic activity and selectivity for CO2RR. Interface engineering has been proven as an effective method to prompt charge transfer by constructing interfaces within the catalysts that is widely used in many electrochemical reactions. The introduced interfaces would benefit the electronic interaction at the interface and assist the electron redistribution, thus optimizing the electronic structure and boosting the interfacial charge transfer. Herein, we report the heterostructure of Bi2S3-Bi2O3 nanosheets (BS-BO NSs) with substantial interfaces for the efficient CO2-to-formate conversion. The rapid-interfacial charge transfer induced by the abundant interfaces not only optimizes electronic structure, but also accelerates the kinetics of CO2RR and improves the electrocatalytic activity and selectivity. Compared with the separate Bi2O3 and Bi2S3 electrocatalysts, BS-BO NSs shows desirable selectivity to formate with a maximum Faradaic efficiency of 93.8 % at a moderate potential. The CO2RR performance is further boosted by using a flow cell system. The high selectivity with large current density makes BS-BO NSs a promising candidate for the practical application of CO2RR in the formate formation.