| Summary: | Electrochemical reduction of CO2 (CO2RR) coupled with renewable electrical energy is an attractive way of upgrading CO2 to value-added chemicals and closing the carbon cycle. However, CO2RR electrocatalysts still suffer from high overpotential, and the complex reaction pathways of CO2RR often lead to mixed products. Early research focuses on tuning the binding of reaction intermediates on electrocatalysts, and recent efforts have revealed that the design of electrolysis reactors is equally important for efficient and selective CO2RR. In this review, we present an overview of recent advances and challenges toward achieving high activity and high selectivity in CO2RR at ambient conditions, with a particular focus on the progress of CO2RR electrocatalyst engineering and reactor design. Our discussion begins with three types of electrocatalysts for CO2RR (noble metal-based, none-noble metal-based, and metal-free electrocatalysts), and then we examine systems-level strategies toward engineering specific components of the electrolyzer, including gas diffusion electrodes, electrolytes, and polymer electrolyte membranes. We close with future perspectives on catalyst development, in-situ/operando characterization, and electrolyzer performance evaluation in CO2RR studies.
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