Graphitic Carbon Nitride Decorated with Nickel(II)-(3-Pyridyl) Benzimidazole Complexes and Pt Nanoparticles as a Cocatalyst for Photocatalytic Hydrogen Production from Water Splitting

Graphitic carbon nitride (g-C3N4) is regarded as a promising and suitable photocatalyst in the progress of hydrogen evolution from water splitting by employing visible-light irradiation. Nevertheless, the fast recombination rate of charge carriers of g-C3N4 results in a low H-2 production rate. In this work, a high efficiency type-II heterostructured photocatalyst is constructed by decorating nickel(II)-(3-pyridyl) benzimidazole (NPBIm) complexes and platinum as a cocatalyst of g-C3N4 nanosheets via the strategy of pi-pi interaction, and the interfacial charge transfer through g-C3N4/NPBIm interface is thus improved. The optimal sample with 6 wt % NPBIm loadings with visible-light irradiation (lambda >= 420 nm) possesses a maximum H-2 production rate of 46.97 mu mol h(-1), which is 3.5-fold higher than that of g-C3N4 alone (13.47 mu mol h(-1)) with a quantum efficicency of 5.13% at 420 nm. Meanwhile, C3N4/6 wt % NPBIm hybrid nanocomposite exhibits good photocatalytic stability toward hydrogen production under visible-light irradiation, demonstrating that the type-II heterojunction photocatalyst has great potential in the practical applications. The separation and migration of photoinduced excitons are significantly enhanced between g-C3N4 and NPBIm nanosheets, as clearly revealed by photoluminescence (PL) spectra, time-resolved PL spectra, and photoelectrochemical results. Overall, this study could provide opportunity to design and develop other highly efficient type-II heterostructured photocatalyst for the enhancement of H-2 evolution from H2O splitting under visible-light irradiation.