Surface plasmon resonance enhanced direct Z-scheme TiO2/ZnTe/Au nanocorncob heterojunctions for efficient photocatalytic overall water splitting

Abstract

Solar-driven photocatalytic overall water splitting is regarded as one of the ideal strategies to generate renewable hydrogen energy without the initiation of environmental issues. However, there are still a few remaining challenges to develop wide-light-absorption and stable photocatalysts for the simultaneous production of H₂ and O₂ in pure water without sacrificial reagents. Herein, we report the design and preparation of Z-scheme TiO₂/ZnTe/Au nanocorncob heterojunctions by homogeneously decorating Au nanoparticles onto the surface of core–shell TiO₂/ZnTe coaxial nanorods for highly efficient overall water splitting. With the appropriate band structure of TiO₂/ZnTe heterojunctions and the surface plasmon resonance enhancement of Au nanoparticles, the well-designed TiO₂/ZnTe/Au nanocorncob heterojunctions can synergistically make effective utilization of broad-range solar light illunimation and enhance the separation efficency of electron–hole pairs, as evidenced by UV-Vis absorption and time-resolved photoluminescence spectroscopy. Photoelectrochemical characterization confirms that the water-splitting reaction on TiO₂/ZnTe/Au nanocorncobs is mainly carried out via a two-electron/two-electron transfer process with an intermediate product of H₂O₂. As a result, the TiO₂/ZnTe/Au nanocorncob photocatalyst can generate H₂ and O₂ with a stoichiometric ratio of 2 : 1 under light irradiation without any sacrificial agents, exhibiting a high H₂ production rate of 3344.0 μmol g⁻¹ h⁻¹ and a solar-to-hydrogen (STH) efficiency of 0.98%. Moreover, the TiO₂/ZnTe/Au nanocorncob heterojunctions show high stability and well-preserved morphological integrity after long-term photocatalytic tests. This study provides a prototype route to produce clean hydrogen energy from only sunlight, pure water, and rationally-designed heterojunction photocatalysts.