Enhancing formate yield through electrochemical CO2 reduction using BiOCl and g-C3N4 hybrid catalyst

Electrochemical carbon dioxide (CO₂) reduction with bismuth-based catalysts has been widely investigated in the recent few years. This is due to bismuth’s ability to perform selective electrochemical CO₂ reduction reaction (eCO₂RR) to an important C₁ product, the formate (HCOO^–). However, boosting the performance of such catalysts is a continuous investigation. In this work, enhancing the active sites for eCO₂RR is investigated by forming nanocomposites with graphitic carbon nitride (g-C₃N₄). BiOCl is synthesized by a simple wet-chemical approach in the presence of glycine as size-controlling agent and formed into nanocomposites, which were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Infrared (IR) Spectroscopy and N₂ physisorption. Linear Sweep Voltammetry (LSV) in argon and CO₂-saturated atmosphere showed higher current values in the case of CO₂. Chronoamperometries (CA) were recorded at −1.06 V vs Reversible Hydrogen Electrode (RHE) for 5400 s obtaining Faradic Efficiencies (FE) varying in the range of 70–77 % depending on the nanocomposites’ composition. In fact, 52.1 wt% BiOCl/g-C₃N₄ formed the highest yields for formate (with also the highest rate of formation of formate) together with a minimal production of H₂ and CO. The effect of nano-structuration induced by glycine, used as a size-controlling agent, to form nanoplates was crucial: microplates of BiOCl produced without glycine showed an FE of 4 %, reaching 85 % in the case of the nanoplates. Post-electrocatalysis characterization revealed the possible role of Bi₂O₂CO₃ as the active phase for eCO₂RR.