Insights into atomically dispersed reactive centers on g-C₃N₄ photocatalysts for water splitting

Co-catalysts decorations provide unique opportunity in promoting the photocatalytic water splitting performance of graphite carbon nitride (g-C₃N₄) system, while mechanistic understanding of this complex catalytic network remains elusive. Here, taking the single-atom-based photocatalysts (M₁-g-C₃N₄) as an unprecedented simplified model system, we theoretically tracked the photocatalytic kinetics for a comprehensive understanding of the photocatalytic process and afforded the descriptor α_S1-T1/α_T1-S0 (ratio of the extent of S₁-T₁ and T₁-S₀ state mixing) and ΔG_H∗ (hydrogen adsorpti on free energy) for rational screening of photocatalysts. The targeted Fe₁-g-C₃N₄ yields an excellent H₂ evolution rate (ca. 3.2 ⋅mmol·g_cat⁻¹·h⁻¹ under full arc), two order of magnitude improvement relative to pristine g-C₃N₄ counterpart and also outperforms other representative 3d-transition-metal-based photocatalysts. This work presents a comprehensive understanding of the essential role of isolated atomic sites in the photocatalytic course and sheds light on the design of photocatalysts from both photophysical and photochemical aspects.