Efficient electroreduction of CO2 by single-atom catalysts two-dimensional metal hexahydroxybenzene frameworks: A theoretical study

Highlights: • The 2D-MOFs of M₃(HHB)₂ were investigated as the electrocatalysts for CO₂ reduction. • The detailed CO₂RR pathway on M₃(HHB)₂ was analyzed. • The M₃(HHB)₂ (M = Cr, Mo, Ru, and Rh) show superior catalytic performance for CO₂ reduction. Electrochemical CO₂ reduction provides a feasible technology for alleviating the energy crisis and global warming, as well as sustainable production of fuels. However, a tremendous challenge is to explore the highly efficient catalysts. Herein, on the basis of density functional theory (DFT) calculations, the catalytic performance of a series of M₃(hexahydroxybenzene)₂ (M₃(HHB)₂) complex nanosheets as the CO₂ reduction reaction (CO₂RR) catalysts was systemically evaluated. The results demonstrated that the catalytic activity of M₃(HHB)₂ depends on the intensity of interaction between CO₂RR intermediates and metal atoms, and can be adjusted by changing the metal atoms. Among the studied candidates, M₃(HHB)₂ (M = Cr, Mo, Ru, and Rh) are predicted to be potential electrocatalysts toward the CO₂RR due to low limiting potential of −0.49, −0.67, −0.63, and −0.68 V, respectively, which are comparable to that of other reported CO₂RR catalysts. In particular, CH₄ is the favorable product on M₃(HHB)₂ (M = Cr and Mo) via *HCOO pathway, while the main product of M₃(HHB)₂ (M = Ru and Rh) is CH₃OH via *COOH channel. It is expected that our investigations could provide meaningful guidance for developing CO₂RR electrocatalysts.