Design of highly efficient g-C3N4-based metal monoatom catalysts by two extra-NM1 atoms: density functional theory simulations

Abstract

Graphitic carbon nitride (g-C₃N₄) is recognized as a favorable substrate for monoatom catalysts due to its uniform nanoholes for anchoring metal monoatoms, while the oxygen evolution reaction (OER) overpotential (η^OER) values of g-C₃N₄-based metal monoatom catalysts are still large. To reduce the η^OER values, a class of novel TM₁NM₁NM₁/g-C₃N₄ was designed via density functional theory simulations, where TM₁ = Fe₁, Co₁ or Ni₁ and NM₁ = C₁, N₁ or O₁. Contributing by two extra-NM₁ atoms, the OER catalytic activities of these materials were effectively improved owing to the shortened TM₁–NM bonds and weakened chemical activity of TM₁ atoms. Based on the volcano activity relationship between the theoretical overpotential (η^OER) and d band center of the TM₁ atom (ε_d), the chemical activity of TM₁ atoms needs to be adjusted to a suitable magnitude (ε_d near −4.883 eV) for a good catalytic activity. The designed Fe₁C₁O₁/g-C₃N₄ with the ε_d of −4.893 eV exhibited an excellent OER catalytic activity of η^OER = 0.219 V. This strategy was applied to devise the reaction active sites and highly efficient catalysts by adjusting the chemical activity of the TM₁ atom with suitable extra-NM₁ atoms.