Enrichment Strategies for Efficient CO₂ Electroreduction in Acidic Electrolytes

Abstract

Electrochemical CO2 reduction reaction (CO2RR) has been recognized as an appealing route to remarkably accelerate the carbon‐neutral cycle and reduce carbon emissions. Notwithstanding great catalytic activity that has been acquired in neutral and alkaline conditions, the carbonates generated from the inevitable reaction of the input CO2 with the hydroxide severely lower carbon utilization and energy efficiency. By contrast, CO2RR in an acidic condition can effectively circumvent the carbonate issues; however, the activity and selectivity of CO2RR in acidic electrolytes will be decreased significantly due to the competing hydrogen evolution reaction (HER). Enriching the CO2 and the key intermediates around the catalyst surface can promote the reaction rate and enhance the product selectivity, providing a promising way to boost the performance of CO2RR. In this review, the catalytic mechanism and key technique challenges of CO2RR are first introduced. Then, the critical progress of enrichment strategies for promoting the CO2RR in the acidic electrolyte is summarized with three aspects: catalyst design, electrolyte regulation, and electrolyzer optimization. Finally, some insights and perspectives for further development of enrichment strategies in acidic CO2RR are expounded.

Operando Observation of (Bi)carbonate Precipitation during Electrochemical CO2 Reduction in Strongly Acidic Electrolytes

“…Recently, several studies advocated the use of acidic electrolytes as a potential strategy to mitigate these unwanted CO 2 losses and avoid (bi)­carbonate precipitation. − In parallel, other studies, as well as mass transport and reaction kinetics considerations, suggest that the local environment around the catalyst has to be basic to activate CO 2 RR and to suppress the parasitic hydrogen evolution reaction (HER), , although then (bi)­carbonate precipitation should be expected also in acidic electrolytes. These processes have not been confirmed through experiments, probably due to the complexity of probing the local phenomena in real-time conditions with enough resolution.…”