Acidic Electrocatalytic CO2 Reduction Using Space-Confined Nanoreactors

Electrochemical CO2 reduction reaction (CO2RR) is an attractive strategy for sustainable production of chemicals and has mainly been implemented in alkaline or neutral electrolytes. However, part of input CO2 is consumed by the formation of carbonate under these conditions. Herein, a space-confined strategy is proposed for CO2RR in acidic media, and Ni nanoparticles are encapsulated inside N-doped carbon nanocages as yolk-shell nanoreactors. By confining CO2RR in the cavities of nanoreactors, a Faradaic efficiency (FE) of 93.2% for CO is achieved at pH 7.2 and 84.3% FE for CO at pH 2.5. The inhibited proton diffusion within the Nernst layer of a nanoreactor is responsible for suppression of competing hydrogen evolution in acid. Moreover, CO2RR in an acidic flow electrolysis system offers enhanced current density and sustainable operation, in comparison with the conventional neutral pH system. This work shows that steering of mass transport via a unique structure is a viable avenue toward selective CO2 conversion, and it provides a further understanding of the structure-performance relationship of electrocatalysts.