Boosting solar-driven water splitting via spatially separated noble-metal-free-based dual reaction sites in cactus-like hollow TiO2

Noble-metal-free sulfides have certain photocatalytic activities and can be used as cocatalysts in reduction reactions. Metal sulfides have a catalytic mechanism similar to that of noble metals, and S ions can exert a force on H+ in water, improving the adsorption capacity of the catalyst for water molecules; this is beneficial to the hydrogen evolution reaction. Moreover, metal oxides can accelerate the consumption of holes and improve the efficiency of electron-hole separation. Herein, a novel TiO2 nanomaterial with a cactus-like hollow structure and with spatially separated MoS2 and NiO dual cocatalysts (denoted as NiO/TiO2/MoS2) is reported for use in catalytic hydrogen evolution under solar light irradiation. Space-separated dual reaction sites (MoS2 and NiO) with redox capability can efficiently promote the separation of photogenerated carriers of the catalyst. Furthermore, the special hollow structure enhances the solar light absorption efficiency by reducing the penetration loss to narrow the band gap. The density functional theory (DFT) calculation results show that, compared to Pt, the MoS2 cocatalyst loaded on the TiO2 surface is more conducive to efficient proton/electron transfer and easier molecular hydrogen release. As a result, the supported MoS2 cocatalyst on TiO2 has comparable photocatalytic hydrogen evolution performance to the noble metal Pt.