Integrated design for electrocatalytic carbon dioxide reduction

Abstract

The electrocatalytic carbon dioxide reduction reaction (CO₂RR) to produce valuable fuels and chemicals with renewable energy inputs is an attractive route to convert intermittent green energy sources (e.g., solar and wind) to chemical energy, alleviate our dependence on fossil fuels, and simultaneously reduce net carbon dioxide emission. However, the generation of reduced multi-carbon products with high energy density and wide applicability from the CO₂RR, such as oxygenates and hydrocarbons, suffers from high overpotential, slow reaction rate, and low selectivity due to its intrinsic multi-electron transfer nature. Moreover, the involved anodic oxygen evolution reaction (OER) also requires large overpotential and its product O₂ bears limited economic value. The potentially generated reactive oxygen species (ROS) during the OER may also degrade the membrane of a CO₂ reduction electrolyzer. Herein, we review the recent progress in novel integrated strategies to address the aforementioned challenges in the electrocatalytic CO₂RR. These innovative strategies include (1) concurrent CO₂ electroreduction via co-feeding additional chemicals besides CO₂ gas, (2) tandem CO₂ electroreduction utilizing other catalysts for converting the in situ formed products from the CO₂RR into more valuable chemicals, and (3) hybrid CO₂ electroreduction through integrating thermodynamically more favourable organic upgrading reactions to replace the anodic OER. We specifically highlight these novel integrated electrolyzer designs instead of focusing on nanostructured engineering of various electrocatalysts, in the hope of inspiring others to approach CO₂ electroreduction from a holistic perspective. The current challenges and future opportunities of electrocatalytic CO₂ reduction will also be discussed at the end.