Fig. 3.

DFT calculation results and reaction scheme. a Optimized configurations of I CO₂, II HCOO*, III HCOOH*, IV HCOOH on (101) facet of pure indium (In) and V CO₂, VI HCOO*, VII HCOOH*, VIII HCOOH on (101) facet sulfur-doped indium (S–In). b Gibbs free energy diagrams for CO₂RR to HCOOH on In (101) and S−In (101) surfaces. c Gibbs free energy diagrams for CO₂RR to CO on In (101) and S−In (101) surfaces. d Gibbs free energies for the formation of H* on pure In (101), In and S sites of S−In (101) surfaces. e Schematic illustration for the role of S²⁻ in promoting water dissociation and H* formation for the reduction of CO₂ to formate. Free energies of b, c and d are shown relative to gas CO₂ and H₂. The green, yellow, gray, red, and blue balls represent In, S, O, C, and H