High-selectivity electrochemical CO2 reduction to formate at low overpotential over Bi catalyst with hexagonal sheet structure

Abstract

The electrochemical conversion of CO2 to formate still suffers from poor selectivity, low production rate, and high overpotential. In this study, a facile strategy is developed to obtain Bi catalysts with a hexagonal sheet structure on copper foil via the constant potential electrodeposition method. The electrocatalyst shows high activity for formate production from CO2 reduction, with the formate faradaic efficiency (FE) reaching nearly 100% at an overpotential of 0.65 V; a high production rate of 96.37 μmol· h−1·cm−2 is obtained, and the corresponding power consumption is as low as 3.64 kW·h·kg−1. The excellent catalytic ability is derived from the sharp edges and corner sites of the catalyst, as they provide numerous surface-active sites and increase the electrical conductivity and local electric field intensities of the surface electrode; thus, the electrochemically active surface area (ECSA) and the electron-donating ability of the Bi electrode are enhanced, while the competing hydrogen evolution reaction (HER) is significantly inhibited. Moreover, the Bi sheets show excellent stability in 24 h electrolysis, with a formate FE of ≥95.8% in aqueous 0.1 M KHCO3 solution. This work indicates that structural adjustment is a critical factor in enhancing the electrocatalytic performance of metallic Bi.