Constructing a 2D/3D Ni ₁₂ P ₅ /CdIn ₂ S ₄ ohmic junction for enhanced photocatalytic selective oxidation of 5-hydroxymethylfurfural and H ₂ production

In this study, a 2D/3D Ni₁₂P₅/CdIn₂S₄ (NP/CIS) ohmic junction heterostructure was successfully constructed <i>via</i> a self-assembly strategy and applied to the photocatalytic co-production of H₂ and high value-added chemical 2,5-diformylfuran (DFF) by selective oxidation of 5-hydroxymethylfurfural (HMF). The ohmic junction formed between metallic Ni₁₂P₅ and semiconductor CdIn₂S₄ significantly augmented the photo-generated charge separation and transport. With visible light irradiation (<i>λ</i> ≥ 400 nm), the optimized 5% NP/CIS composite exhibited outstanding H₂ evolution rates (561.3 µmol g^-1 h^-1) and DFF formation rate (532.3 µmol g^-1 h^-1), representing a 4.5-fold and 5.3-fold increase compared to the pure CIS material, while maintaining high selectivity (>85%) and excellent cycling stability. Comprehensive characterization techniques and mechanistic studies revealed that the ohmic junction facilitated rapid electron transfer from CIS to NP, suppressed charge recombination, provided abundant active sites, and lowered the overpotential for hydrogen evolution. Furthermore, the retained holes from the valence band in CIS effectively drove the selective dehydrogenation reaction of HMF to DFF <i>via</i> a carbon radical mechanism. This work delved into the design principles of highly efficient ohmic junction photocatalysts, offering a highly promising strategy for synergistically achieving biomass conversion and clean energy production.