Effect of halogen-modification on Ag catalyst for CO₂ electrochemical reduction to syngas from NH₄HCO₃ electrolyte

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 to −0.7 V), which is beneficial to apply to different industrial production.