Concurrent Electrolysis under Pressured CO2 for Simultaneous CO2 Reduction and Hazardous SO2 Removal

Abstract

Although elevating CO2 pressure facilitates electrochemical CO2 reduction reaction (CO2RR), the paired anodic oxygen evolution reaction (OER) can hardly gain the benefit due to its sluggish kinetics at near-neutral pH. Here, we replaced the OER with sulfite electrooxidation reaction (SOR) at near-neutral pH to realize a CO2/sulfite concurrent system, which can serve as a promising strategy for the dual treatments of CO2 and SO2 in flue gas. The anodic SOR reaction catalyzed by the non-noble nanoporous NiO supported on the nickel foam electrode exhibited a voltage saving by ∼1 V in contrast to the OER at 50 mA cm–2. On the other hand, BiOI-catalyzed cathodic CO2-to-formate conversion at 20 bar CO2 offered a remarkably broadened potential range and enhanced current density in contrast to the results tested at 1 bar CO2. An overall electricity-to-formate energy conversion efficiency of 65% for the CO2RR + SOR system was successfully obtained at a cell voltage of 1.8 V, which is 20% higher than that of the CO2RR + OER system. Based on these, an efficient and energy-saving full electrolysis system for concurrent electrolysis of CO2RR and SOR at 20 bar CO2 has been successfully constructed.