Unraveling the Microstructure‐Property Relationship of Fe Single‐Atoms via Introducing Asymmetric P‐Coordination for Photocatalytic Hydrogen Evolution

Abstract The local atomic environments of single‐atom photocatalysts play a decisive role in determining the solar‐to‐hydrogen energy conversion efficiency. However, controllably modulating the microstructure of single‐atom sites to enhance catalytic activity and deeply understanding the structure‐property relationship remain great challenges. Herein, electron‐rich P atoms are introduced to accurately regulate the local coordination environment and electronic configuration of Fe single atoms and construct a unique asymmetrical FeN₃P₂ motif into carbon nitride (FeN₃P₂‐CN) for significantly improving the photocatalytic H₂ evolution activity and stability. Specifically, in the absence of noble metal cocatalyst and photosensitizer, the FeN₃P₂‐CN achieves a remarkable H₂ evolution rate of 2668.5 µmol g⁻¹ h⁻¹ under visible light irradiation (λ > 420 nm), more than 105 times higher than that of unregulated FeN₄ sample. Systematic characterizations and theoretical calculations unveil that the FeN₃P₂ single‐atom sites not only significantly broaden the photoabsorption region and facilitate the charge separation and interfacial transfer, but also efficiently promote adsorption and activation of H₂O. This work paves a promising pathway to design novel single‐atom photocatalysts at the atomic level for achieving highly efficient water‐splitting performance.