Noble-Metal-Free CdS Decorated Porous Ni_<i>x</i>Co_1–<i>x</i>O Skeleton Derived from Metal–Organic Framework for Efficient Visible-Light H₂ Production

Noble-metal-free CdS@Ni_<i>x</i>Co_1–<i>x</i>O photocatalyst was synthesized for the first time using a metal–organic framework (MOF) to serve as the template for efficient visible-light photocatalytic H₂ production. The entire preparation process mainly involved the calcination of NiCo-MOF and subsequent decoration of CdS nanoparticles (NPs) via hydrothermal treatment. The photoelectrical properties of pristine Ni_<i>x</i>Co_1–<i>x</i>O are optimized. With the introduction of CdS NPs, the H₂ production of CdS@Ni_<i>x</i>Co_1–<i>x</i>O under visible light irradiation (λ > 420 nm) increased significantly from 0 to 2795.6 μmol g^–1 h^–1, thereby indicating an excellent synergistic effect between CdS and the Ni_<i>x</i>Co_1–<i>x</i>O skeleton. The band gap of CdS in the CdS@Ni_<i>x</i>Co_1–<i>x</i>O samples can be narrowed to ca. 1.54 eV. Compared with Ni_<i>x</i>Co_1–<i>x</i>O, CdS@Ni_<i>x</i>Co_1–<i>x</i>O presents an enhanced electron paramagnetic resonance (EPR) peak and low photoluminescence (PL) spectrum, directly proving its excellent charge carriers separation ability. Besides, the large specific surface area (703.27 m² g^–1) and mesoporous structure (ca. 3–4.5 nm in diameter) of CdS@Ni_<i>x</i>Co_1–<i>x</i>O can expose more active sites and serve as channels for the access of reactants, accelerating the water-cracking reduction reaction also. Furthermore, the H₂ evolution performances of CdS@Ni_<i>x</i>Co_1–<i>x</i>O under visible light (λ > 400 nm) and full spectrum light are studied as well. On the basis of experiment and density functional theory (DFT) calculation results, a feasible mechanism is tentatively proposed. This work suggests the great application prospects of NiCo-MOF-based hybrid in water splitting.