Strategies of improving carbon utilization efficiency in electrocatalytic CO₂ reduction

Renewable energy-driven electrocatalytic CO2 reduction to valuable fuels and chemicals is an important route to achieve carbon neutrality. The state-of-the-art alkaline electrocatalytic CO2 reduction technology currently suffers from severe carbon loss issue. The low carbon utilization efficiency has been considered as a bottleneck issue in electrocatalytic CO2 reduction reaction, especially in the case of alkaline membrane electrode assembly (MEA) electrolyzers towards practical application. In this article, we provide an in-depth analysis of the sources of carbon loss and discuss a group of innovative strategies that have been proposed for improving CO2 utilization efficiency, namely, developing new reaction routes for electrocatalytic CO2 reduction such as acidic electrolysis, bipolar membrane electrolysis, acid-alkaline tandem electrolysis, high-low temperature tandem electrolysis, all liquid phase anodic reaction, and in-situ recovery of transmembrane CO2. The main point is to avoid CO2 conversion to carbonate or to recover carbon loss during reaction. While these strategies have improved CO2 utilization efficiency to some extent, but at a cost of other performance metrics such as Faradaic efficiency, current density, energy efficiency, and long-term stability. Future research should fully integrate the rational design of electrolyzers with the rational design of catalyst and electrode structures at a crossed scale from macro- to meso- and microscale. The CO2 utilization efficiency should be further improved based on the excellent performance of current alkaline MEA electrolyzers.