Integrated "Two-in-One" Strategy for High-Rate Electrocatalytic CO₂ Reduction to Formate

The electrochemical CO₂ reduction reaction (ECR) is a promising pathway to producing valuable chemicals and fuels. Despite extensive studies reported, improving CO₂ adsorption for local CO₂ enrichment or water dissociation to generate sufficient H* is still not enough to achieve industrial-relevant current densities. Herein, we report a "two-in-one" catalyst, defective Bi nanosheets modified by CrO_x (Bi-CrO_x), to simultaneously promote CO₂ adsorption and water dissociation, thereby enhancing the activity and selectivity of ECR to formate. The Bi-CrO_x exhibits an excellent Faradaic efficiency (≈100 %) in a wide potential range from -0.4 to -0.9 V. In addition, it achieves a remarkable formate partial current density of 687 mA cm^-2 at a moderate potential of -0.9 V without iR compensation, the highest value at -0.9 V reported so far. Control experiments and theoretical simulations revealed that the defective Bi facilitates CO₂ adsorption/activation while the CrO_x accounts for enhancing the protonation process via accelerating H₂O dissociation. This work presents a pathway to boosting formate production through tuning CO₂ and H₂O species at the same time.