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

• BiOCl/g-C 3 N 4 nanocomposties have been prepared using glycine as structural-directing agent. • Nanocomposites are active and selective to HCOOH in the electrochemical reduction of CO 2 . • The material with 52.1 wt% of BiOCl produces 300 mmol/g of HCOOH in 1.5h with a Faradic Efficiency of 77% at -1.06V vs RHE. • The active phase is strongly modified under operative conditions, evolving into Bi 2 O 2 CO 3 and metal Bi. Electrochemical carbon dioxide (CO 2 ) 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 CO 2 reduction reaction (eCO 2 RR) to an important C 1 product, the formate (HCOO – ). However, boosting the performance of such catalysts is a continuous investigation. In this work, enhancing the active sites for eCO 2 RR is investigated by forming nanocomposites with graphitic carbon nitride (g-C 3 N 4 ). 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 N 2 physisorption. Linear Sweep Voltammetry (LSV) in argon and CO 2 -saturated atmosphere showed higher current values in the case of CO 2 . 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-C 3 N 4 formed the highest yields for formate (with also the highest rate of formation of formate) together with a minimal production of H 2 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 Bi 2 O 2 CO 3 as the active phase for eCO 2 RR.