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

Abstract

Although elevating CO 2 pressure facilitates electrochemical CO 2 reduction reaction (CO 2 RR), 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 CO 2 /sulfite concurrent system, which can serve as a promising strategy for the dual treatments of CO 2 and SO 2 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 CO 2 -to-formate conversion at 20 bar CO 2 offered a remarkably broadened potential range and enhanced current density in contrast to the results tested at 1 bar CO 2 . An overall electricity-to-formate energy conversion efficiency of 65% for the CO 2 RR + SOR system was successfully obtained at a cell voltage of 1.8 V, which is 20% higher than that of the CO 2 RR + OER system. Based on these, an efficient and energy-saving full electrolysis system for concurrent electrolysis of CO 2 RR and SOR at 20 bar CO 2 has been successfully constructed.

Influence of Environmental Conditions on Electrocatalytic CO2 Reduction

“…However, for the sensitive electrocatalytic CO 2 RR, environmental conditions also play an important role in the reaction process. Many researchers have recognized the effects of changing conditions such as temperature, [43] pressure, [44] type of reactor, [45] and type of inlet gas on the electrocatalytic CO 2 RR. [46] For example, properly adjusting the temperature and pressure can increase the reaction rate, but also result in increased side reactions or decreased product selectivity.…”