Photoassisted Electrochemical Hydrogen Evolution Reaction of MFe₂O₄@Ultrathin Black Phosphorus Amorphous–Crystalline Interface

Exploring highly active, stable, and low-cost catalysts for photoelectrochemical hydrogen evolution reaction (PE-HER) is vital in the field of energy conversion. Herein, we construct a new amorphous crystalline interface that amorphous iron-based spinel oxide (A-MFe2O4 (M = Ni, Co, Zn)) is uniformly anchored on the crystalline exfoliated black phosphorus (C-EBP) nanosheets via electrochemical and solvothermal strategies. Among these A-MFe2O4@C-EBP catalysts, more oxygen defects of A-NiFe2O4@C-EBP interface provide a larger effective electrochemical active area of 32.33 mF cm–2 as well as a turnover frequency of 0.44 s–1 and allow for an optimum equilibrium of the hydrogen-containing adsorption intermediates. Furthermore, A-NiFe2O4@C-EBP exhibits significant PE-HER performance with an overpotential of 42 mV at 10 mA cm–2 under visible-light irradiation. Density functional theory (DFT) calculations show that the amorphous–crystalline composite structure causes a large number of oxygen defects enhancing the intrinsic activity of A-NiFe2O4@C-EBP, which A-NiFe2O4@C-EBP significantly improves its adsorption capacity for H* for HER and has the lowest Gibbs free energy change for HER. This study not only provides a superior multifunctional amorphous–crystalline interface catalysts but also helps to understand the catalytic mechanism of PE-HER.