Mechanistic insights into C-C coupling in electrocatalytic CO₂ reduction reaction

The utilization of CO₂ has become an emerging area of research in response to climate change and global warming. The electrochemical CO₂ reduction reaction (CO₂RR) holds significant promise as a technology to address this issue by converting CO₂ molecules into various commercially valuable chemicals. While CO₂RR to C₁ hydrocarbons has achieved high activity and selectivity, the C-C coupling to produce higher hydrocarbons remains challenging due to low energy efficiency and the prevalent hydrogen evolution reaction (HER) on the same catalyst, leading to high hydrogenation rates. In this review, we aim to elucidate the fundamental challenges of C-C coupling and explore potential strategies to enhance the selectivity for higher hydrocarbon products. We discuss the mechanisms underlying the formation of C₂ and C₃ products, focusing on molecular catalysts that facilitate C-C coupling by positioning CO₂ molecules in close proximity. Additionally, we provide a comprehensive overview of different approaches to improve higher hydrocarbon selectivity, along with future suggestions and recommendations for new researchers in the field. This review serves as a valuable resource for both academic researchers and industrial stakeholders aiming for the commercialization of CO₂RR technologies.