Elucidating the activation of BiOX (with X = Br, Cl) electrocatalysts for selective CO2 to formic acid conversion through in situ X-ray abso

Bismuth (Bi)-based catalysts have the potential to produce formic acid through electrochemical CO2 conversion. The inevitable reconstruction of catalysts under working conditions is unfortunately not well understood, resulting in inaccurate understanding of structure-property relationships. Here, we fabricated two-dimensional Bi oxyhalides electrocatalysts, i.e.BiOBr (BOB) and BiOCl (BOC). A selectivity (97%) of CO2 to formic acid was obtained with current density up to 156 mA/cm2 on BOB, whereas BOC displayed a lower selectivity (80%) with current density of 116 mA/cm2. In order to elucidate the real active sites, we propose to perform in situ X-ray Absorption Spectroscopy at the Bi L3 edge. Together with the in situ X-ray diffraction study we have conducted, a link will be built between the different catalytic behavior and the nature of catalytically active sites in the studied catalysts, which would pave the way for the rational design of next-generation electrocatalysts.