Regulation of electrical double layers promotes electrochemical reduction of carbon dioxide

Abstract

The electrochemical CO2 reduction reaction is an effective approach to alleviate global energy shortage and environmental problems by converting CO2 to high value-added products. The rational design of nanostructured electrocatalysts requires an understanding of the interplay between mass transfer and reaction in a confined environment. Here, local pH and CO2 concentration are considered as the typical descriptors of reaction environment, which are modelled using the reaction-coupled modified Poisson-Nernst-Planck equations in an isolated nanopore. The effect of nanoconfinement, steric hindrance and electrical double layer on the CO2RR as well as the competitive hydrogen evolution reaction are investigated. An optimal local reaction environment with high Faradaic efficiency and selectivity is found when the pore radius is comparable to the Debye length. Our work provides microscopic insights into the interplay between diffusion, migration, and reaction under the nanoconfinement of nanopores.