Fabrication of novel Ni@NiO hollow structure in NiS/CdZnS catalytic system via NH3-reduction strategy for efficient photocatalytic H2 production

Ingenious construction of Ni@NiO cocatalyst structure through reduction strategies remains a challenge in Nickel-based photocatalysis. Herein, a melamine sponge NH3-reduction strategy was proposed for the fabrication of novel Ni@NiO hollow structure in NiS/CdZnS catalytic system on C(N) skeleton. Melamine sponge was used as catalyst carrier and reducing agent precursor simultaneously. Photochemical tests showed that Ni@NiO/NiS/CdZnS@C(N) achieves an optimal H2 production rate (34456 μmol h−1 g−1), 3.78 times that of pristine CdZnS (9126 μmol h−1 g−1). The Z-scheme mechanism optimizes the electron distribution of the photocatalyst, thereby enhancing electron transfer efficiency. Based on the DFT calculations, a feasible reaction mechanism for Ni@NiO/NiS/CdZnS@C(N) was proposed. The NiS surface was found to be more favorable for H2O adsorption, while the Gibbs free energy ΔGH* on the NiO side was only −0.36 eV, which was conducive to H2 formation. Moreover, Ni@NiO/NiS/CdZnS@C(N) exhibited enhanced DOS near the Fermi level, indicating that its electrical property is significantly improved.