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-1g-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.