Heterophase-structured bismuth nanosheets for solar energy-driven electrocatalytic reduction of CO₂ to formate

Exploring efficient catalysts for the electrochemical CO2 reduction reaction (CO2RR) to formate is highly imperative but challenging. Herein, a bismuth-nanosheet network with abundant crystalline-amorphous boundaries (c-a Bi-NSs) was newly prepared through facile in situ electrochemical reduction of a two-dimensional lamellar bismuth coordination polymer. In a typical H-type cell, the as-reconstructed c-a Bi-NSs electrocatalyst delivered a faradaic efficiency of >90% for formate over a broad potential window ranging from -0.8 to -1.4 V vs. a reversible hydrogen electrode as well as good operating durability. Meanwhile, in a flow cell, a high selectivity of formate generation with a maximum partial current density exceeding 325 mA cm(-2) was achieved, outperforming most reported Bi-based electrocatalysts. When coupling with a photovoltaic device, a full-cell based on the anodic formaldehyde oxidation reaction (FOR) and cathodic CO2RR using Cu foam and c-a Bi-NSs as electrocatalysts was fabricated, and it displayed remarkable dual electrocatalysis performance for formate production, indicating bright application prospects. This study demonstrates a guiding strategy for the design of highly efficient catalysts and advanced electrolytic systems.