Mass-transfer-enhanced hydrophobic Bi microsheets for highly efficient electroreduction of CO2 to pure formate in a wide potential window

The industrial application of electrochemical CO2 reduction reaction is challenged by the limited mass transfer and the mixing of products with traditional electrolytes. Here, we propose an in-situ electroreduction strategy to construct hydrophobic Bi microsheets with (012) plane orientation and abundant grain boundaries to solve these problems and maintain high intrinsic activity. The large distance between microsheets and the stable micro-sized hydrophobic structure can trap more air and form smaller solid-liquid interface to stably improve CO2 mass transfer. The obtained Bi microsheets exhibit high activity and selectivity in a wide potential window. In an H-type cell, the selectivity of formate exceeds 90% over a potential range of − 0.8 V to − 1.3 V vs. RHE. The pure formate solution is produced using a CO2 reduction cell with solid-state electrolyte to simplify product separation, and 0.13 M pure formate solution is continuously and stably produced for 110 h at 160 mA cm−2.