Phase Interface Regulating on Amorphous/Crystalline Bismuth Catalyst for Boosted Electrocatalytic CO₂ Reduction to Formate

Electroreduction of carbon dioxide into readily collectable and high-value carbon-based fuels is greatly significant to overcome the energy and environmental crises yet challenging in the development of robust and highly efficient electrocatalysts. Herein, a bismuth (Bi) heterophase electrode with enriched amorphous/crystalline interfaces was fabricated via cathodically in situ transformation of Bi-based metal-phenolic complexes (Bi-tannic acid, Bi-TA). Compared with amorphous or crystalline Bi catalyst, the amorphous/crystalline structure Bi leads to significantly enhanced performance for CO 2 electroreduction. In a liquid-phase H-type cell, the Faraday efficiency (FE) of formate formation is over 90% in a wide potential range from −0.8 to −1.3 V, demonstrating a high selectivity toward formate. Moreover, in a flow cell, a large current density reaching 600 mA cm –2 can further be rendered for formate production. Theoretical calculations indicate that the amorphous/crystalline Bi heterophase interface exhibits a favorable adsorption of CO 2 and lower energy barriers for the rate-determining step compared with the crystalline Bi counterparts, thus accelerating the reaction process. This work paves the way for the rational design of advanced heterointerface catalysts for CO 2 reduction.