Achieving Photocatalytic Overall Nitrogen Fixation via an Enzymatic Pathway on a Distorted CoP₄ Configuration

Photocatalytic nitrogen (N₂) fixation over semiconductors has always suffered from poor conversion efficiency owing to weak N₂ adsorption and the difficulty of N≡N triple bond dissociation. Herein, a Co single-atom catalyst (SAC) model with a C-defect-evoked CoP₄ distorted configuration was fabricated using a selective phosphidation strategy, wherein P-doping and C defects co-regulate the local electronic structure of Co sites. Comprehensive experiments and theoretical calculations revealed that the distorted CoP₄ configuration caused a strong charge redistribution between the Co atoms and adjacent C atoms, minimizing their electronegativity difference. Consequently, the N₂ adsorption pattern switched from an "end-on" to a "side-on" mode with a high N₂ adsorption energy of -1.40 eV and an elongated N-N bond length of 1.20 Å, notably decreasing the N₂ adsorption/activation energy barrier. In the absence of sacrificial agents, the Co SAC achieved excellent photocatalytic overall N₂ fixation performance via an enzymatic pathway. The NH₃ yielding rate peaked at 1249.5 μmol h^-1 g^-1 with an apparent quantum yield of 3.51 % at 365 nm. Moreover, the selective phosphidation strategy has universality for synthesizing other SACs, such as those containing Ni and Fe. This study offers new insight into co-regulating the electronic structure of SACs for efficient photocatalytic overall N₂ fixation.