Hierarchical CdS/Ni₃S₄/Ni₂P@C Photocatalyst for Efficient H₂ Evolution under Visible-Light Irradiation

Structural and morphological modulations play a crucial role in increasing the surface active sites of semiconductor photocatalysts for visible-light-driven water splitting. To fabricate a novel CdS/Ni₃S₄/Ni₂P@C heterostructure, we first prepared carbon-encapsulated Ni₃S₄/Ni₂P (Ni₃S₄/Ni₂P@C) with a high surface area by sequential carbonization and phosphorization of a Ni-metal-organic framework (MOF) precursor. Combined characterization and photoelectrochemical measurement results reveal that the assembly of CdS nanowires and highly porous Ni₃S₄/Ni₂P@C can enhance the visible-light response capability of the CdS/Ni₃S₄/Ni₂P@C heterostructure catalyst by reducing the forbidden band gap of CdS. The hydrogen production rate of 21.56 mmol h^-1 g^-1 for CdS/Ni₃S₄/Ni₂P@C with a Ni₃S₄/Ni₂P@C mass fraction of 10 wt % was 26 times higher than that of CdS in a photolytic aquatic hydrogen system. A possible mechanism for the photocatalytic enhancement of the Ni₃S₄/Ni₂P@C co-catalyst was systematically investigated and discussed. This research opens a new strategy for constructing ternary heterojunction photocatalysts via MOF precursors.