CO2 electrochemical reduction using single-atom catalysts. Preparation, characterization and anchoring strategies: a review

Abstract

Electrochemical reduction of CO2 into value-added chemicals should reduce the consumption of fossil fuels and counteract global warming caused by CO2 generation. Nonetheless, CO2 is rather stable and chemically inert, calling for effective electrocatalysts to avoid problems such as sluggish kinetics, low reaction efficiency and poor product selectivity during CO2 conversion. Recently, single-atom catalysts have shown maximum atom utilization and unique catalytic performance during electrochemical reactions. Catalysts used have been developed from poorly controlled nanoparticles or nanoclusters to isolated atomic structures. Herein, we review the preparation, characterization, anchoring strategies and electrochemical applications of single-atom catalysts. Concerning methods of preparation, the use of organometallic ligands shows high potential for synthesis and industrial applications. Both characterization and calculations using the density functional theory allow to assess the atomic distribution, the coordination environment and the catalytic mechanism. To improve synthesis, we present four anchoring strategies: defect engineering, atom coordination, spatial confinement and sacrifice template. Applications in electrochemical reduction of CO2 to liquid and gaseous products reveal Faraday efficiency higher than 90%, excellent activity, selectivity, stability and kinetic properties.