Effect of Halogen-modification on Ag Catalyst for CO2 Electrochemical Reduction to Syngas from NH4HCO3 Electrolyte

Abstract The crucial technology of combining the excess capacity from power plants and the electrocatalytic reduction method to realize the direct conversion of products from ammonia-based CO2 capture to syngas of CO and H2 is to research and develop catalysts for direct electrochemical NH4HCO3 reduction. The electrochemical performance of halogen (Cl, Br, and I)-modified Ag electrodes by cyclic voltammetry (CV) oxidation and reduction treatment carried out in supersaturated NH4HCO3 electrolyte without CO2 bubbling. All of the halogen-modified catalysts realized the direct reduction of NH4HCO3 to syngas of CO and H2. Among them, the Br-modified Ag catalysts have CO Faradaic efficiency of 74.0% at −0.5 V versus reversible hydrogen electrode much higher than that of Cl- (38%) and I- (39.8%) modified Ag catalysts. The H2/CO ratio on the Br-modified Ag catalyst is approximately 0–3, which is conducive to the reserve of multi-carbon raw materials and the process of Fischer Tropsch synthesis. Furthermore, the Cl-modified Ag catalyst could control the H2/CO ratio of syngas in a wide range of 0.6–6.0 under low potential (from −0.3 V to −0.7 V), which is beneficial to apply to different industrial production.