Photoassisted Electrochemical Hydrogen Evolution Reaction of MFe 2 O 4 @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-MFe 2 O 4 (M = Ni, Co, Zn)) is uniformly anchored on the crystalline exfoliated black phosphorus (C-EBP) nanosheets via electrochemical and solvothermal strategies. Among these A-MFe 2 O 4 @C-EBP catalysts, more oxygen defects of A-NiFe 2 O 4 @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-NiFe 2 O 4 @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-NiFe 2 O 4 @C-EBP, which A-NiFe 2 O 4 @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.