biostudies-literatureWang YPriority Academic Program Development of Jiangsu Higher Education InstitutionsNational Natural Science Foundation of ChinaNational Key Research and Development Program of China6366-6372https://www.ebi.ac.uk/biostudies/studies/S-EPMC9159077biostudies-literatureUnknown13(21)Formate and CO are competing products in the two-electron CO₂ reduction reaction (2e CO₂RR), and they are produced <i>via</i> *OCHO and *COOH intermediates, respectively. However, the factors governing CO/formate selectivity remain elusive, especially for metal-carbon-nitrogen (M-N-C) single-atom catalysts (SACs), most of which produce CO as their main product. Herein, we show computationally that the selectivity of M-N-C SACs is intrinsically associated with the CO₂ adsorption mode by using bismuth (Bi) nanosheets and the Bi-N-C SAC as model catalysts. According to our results, the Bi-N-C SAC exhibits a strong thermodynamic preference toward *OCHO, but under working potentials, CO₂ is preferentially chemisorbed first due to a charge accumulationChemical scienceWhy heterogeneous single-atom catalysts preferentially produce CO in the electrochemical CO₂ reduction reaction.PMC9159077221730482019YFA0308000Li YWang YLiu TfalseWhy heterogeneous single-atom catalysts preferentially produce CO in the electrochemical CO₂ reduction reaction.Formate and CO are competing products in the two-electron CO₂ reduction reaction (2e CO₂RR), and they are produced <i>via</i> *OCHO and *COOH intermediates, respectively. However, the factors governing CO/formate selectivity remain elusive, especially for metal-carbon-nitrogen (M-N-C) single-atom catalysts (SACs), most of which produce CO as their main product. Herein, we show computationally that the selectivity of M-N-C SACs is intrinsically associated with the CO₂ adsorption mode by using bismuth (Bi) nanosheets and the Bi-N-C SAC as model catalysts. According to our results, the Bi-N-C SAC exhibits a strong thermodynamic preference toward *OCHO, but under working potentials, CO₂ is preferentially chemisorbed first due to a charge accumulation2022-01-01T00:00:00Z2022 Jun2025-04-06T19:45:10.336Z2025-04-06T19:45:10.336ZS-EPMC91590773573389310.1039/d2sc01593e