Enhancing mechanism of electron-deficient p states on photocatalytic activity of g-C3N4 for CO2 reduction

Abstract

By utilizing DFT calculations and AIMD simulations, we systematically investigated the photocatalytic activity of B/N2_V-pg-C₃N₄, which is coplanar g-C₃N₄ with an electron-deficient B atom substituted for the nitrogen atom, for CO₂ reduction. Significantly, electronic structure analysis revealed that compared with pristine pg-C₃N₄ (E_g = 2.98 eV), B/N2_V-pg-C₃N₄ had a smaller band gap (E_g = 1.70 eV), where the position of the conduction band minimum (CBM) and valence band maximum (VBM) increased by approximately 0.79 eV and decreased by approximately 0.49 eV, respectively. Catalytic mechanism studies demonstrated that by comparison with the barrier of 1.55 eV in the hydrogen evolution reaction (HER), B/N2_V-pg-C₃N₄ thermodynamically tended to catalyse CO₂ into HCOOH (E_a = 0.86 eV) and HCHO (E_a = 0.86 eV) with high selectivity. Further, isotope effect calculations revealed that B/N2_V-pg-C₃N₄ is an excellent catalyst for the synthesis of deuterium products using CO₂. Thus, the activation of CO₂ in B/N2_V-pg-C₃N₄ is dictated by the curved geometry and its unique electronic-deficient p states, which are beneficial for its excellent photocatalytic performance for CO₂ reduction.