In Situ Dissociated Chalcogenide Anions Regulate the Bi-Catalyst/Electrolyte Interface with Accelerated Surface Reconstruction toward Efficient CO2 Reduction

Understanding the structure change of the electrocatalysts during the electrochemical CO2 reduction reaction (CO2RR) is of crucial importance to illustrate the structure–performance relationship. Here, the reconstruction of Bi–O–M (M = S, Se, or Cl) nanosheets induced by the in situ dissociated chalcogenide anions toward efficient CO2RR to formate is reported. The surface work function and potential of zero charge (PZC) of metallic Bi are reduced upon anions' adsorption, facilitating the regeneration of active Bi–O structures during reduction. Moreover, a correlation between the pKb values of the anions and the local pH of the catalyst/electrolyte interface can be established. The anion with a smaller pKb (S2– < Se2– < Cl–) would induce a more alkaline environment and further promote the formation of Bi–O structures. Among them, Bi2O2S with in situ released S2– during reconstruction exhibits the best CO2RR-to-formate performance with a large current density of 32.7 mA cm–2 at −0.9 VRHE in H-cells, which is 3 times higher than metallic Bi and Bi2O3 without trace S2– and outperforming most of the reported Bi-based catalysts. In the flow cell, the current density can reach more than 280 mA cm–2 at −0.56 VRHE and a 96% average FEformate is achieved at a current density of 150 mA cm–2 in the long-term test. This work provides an approach to regulate the catalyst/electrolyte interface and electrocatalytic performance of metal electrocatalysts through the in situ released anions.