New insights into the electrochemical conversion of CO2 to oxalate at stainless steel 304L cathode

Electrochemical conversion of CO2 to value added chemicals is a promising route for its utilization and mitigation from atmosphere. Nevertheless, an industrial process involving CO2 electroreduction is yet to be a reality and requires further studies on improving the existing processes. In the present work, we report new insights into the electrochemical conversion of CO2 to zinc oxalate at SS 304 L cathode in acetonitrile in the presence of a sacrificial Zn anode. The influence of current density, water content in the electrolyte solution and pressure on product selectivity were evaluated. In addition, oxalic acid synthesis from zinc oxalate was studied using ester hydrolysis process. Our results showed that the product yield is affected due to CO2 reduction to carbonate, decomposition of acetonitrile to cyanide and glycolate formed due to partial reduction of oxalate. Experiments performed in a batch reactor at 2 bar pressure showed that an average Faradaic efficiency of 73.9% can be obtained for zinc oxalate. A yield of 58.1% was obtained for the extraction of oxalic acid. Both zinc oxalate and oxalic acid obtained from this process were compared with commercially available products to confirm its purity.