Towards full-spectrum (UV, visible, and near-infrared) photocatalysis: achieving an all-solid-state Z-scheme between Ag2O and TiO2 using reduced graphene oxide as the electron mediator

Abstract

Making full use of solar energy and achieving high charge separation efficiency are critical factors for the photocatalysis technique. Silver oxide (Ag₂O) was used for photocatalysis due to its broad spectrum response. However, the serious photocorrosion and fast carrier recombination of Ag₂O have limited its practical applications. In this work, we propose a strategy to suppress its photocorrosion and promote charge separation by the construction of an all-solid-state Z-scheme photocatalytic system for photocatalytic degradation of tetracycline (TC) under UV light, visible light, near-infrared (NIR) light and simulated solar light irradiation, which was composed of electron-mediated reduced graphene oxide (RGO)-enwrapped TiO₂ nanobelts (NBs) as UV-responsive photocatalysts and visible/NIR-light-driven Ag₂O nanoparticles (NPs). The improved photoactivity and anti-photocorrosion of RGO–Ag₂O/TiO₂ composites can be attributed to the following: (i) RGO can serve as a charge transmission bridge between Ag₂O and TiO₂, and the Z-scheme keeps the electrons with high reducing capability in the conduction band (CB) of TiO₂ and the holes with high oxidation capability in the valence band (VB) of Ag₂O; (ii) Ag₂O NPs are well photodeposited on the surface of RGO and increase the visible and NIR light absorption via their narrow band gap (1.15 eV); (iii) the Z-scheme electron transport mechanism induced the accumulation of photoinduced holes in the VB of Ag₂O which can protect Ag₂O from photocorrosion. The trapping experiments confirmed that ˙O₂⁻ and h⁺ are the main active species in the photocatalytic degradation of TC.