CO2 Electroreduction to Formate at a Partial Current Density up to 590 mA mg−1 via Micrometer-Scale Lateral Structuring of Bismuth Nanosheets

Abstract

2D bismuth nanosheets are a promising layered material for formate-producing via electrocatalytic CO2 conversion. However, the commercial interest of bismuth nanosheets in CO2 electroreduction is still rare due to the undesirable current density for formate at moderate operation potentials (about 200 mA mg−1) and harsh synthesis conditions (high temperature and/or high pressure). This work reports the preparation of Bi nanosheets with a lateral size in micrometer-scale via electrochemical cathodic exfoliation in aqueous solution at normal pressure and temperature. As-prepared Bi LNSs (L indicates large lateral size) possess high Faradaic efficiencies over 90% within a broad potential window from −0.44 to −1.10 V versus RHE and a superior partial current density about 590 mA mg−1 for formate in comparison with state-of-the-art results. Structure analysis, electrochemical results, and density functional theory calculations demonstrate that the increasing tensile lattice strain observed in Bi LNSs leads to less overlap of d orbitals and a narrower d-band width, which tuning the intermediate binding energies, and therefore promotes the intrinsic activity.