A heterostructured TiO2–C3N4 support for gold catalysts: a superior preferential oxidation of CO in the presence of H2 under visible light irradiation and without visible light irradiation

Abstract

In the present study, a simple method, involving precipitation and a subsequent hydrothermal synthesis, was used to prepare a supported gold catalyst on TiO₂–C₃N₄, which was subsequently evaluated for its performance for CO preferential oxidation in the presence of H₂. It was found that the supported gold catalyst on TiO₂–C₃N₄ nano-hetero-architecture had a higher catalytic activity than that on the counterpart TiO₂ or C₃N₄ alone under visible light irradiation and without visible light irradiation. A better contact between the gold atom arrangement and heterostructured support was clearly observed by transmission electron microscopy (TEM), which suggested as the physical basis for highly efficient electron transfer. Based on the results of ex situ X-ray photoelectron spectroscopy (XPS), redox couple mode (TCNE/TCNE⁻) testing, transient photocurrent and Fourier transform-infrared spectra (FT-IR) of CO adsorption, it was proposed that the nano-heterostructure of TiO₂–C₃N₄ and the localized surface plasmon resonance (LSPR) of Au NPs promoted electron transfer among the interfaces of TiO₂, C₃N₄ and Au NPs, resulting in the higher electron density of Au NPs, followed by the activation of CO adsorbed at the Au sites and the formation of O₂⁻ radical active species. Moreover, the re-combination of Au–H(ad) with the discharge of molecular hydrogen induced by the higher electron densities of Au NPs and the hydrogen spillover of Au–H(ad) to the support in the formation of surface hydroxyl groups could drive the higher selectivity of oxidizing CO. In view of its electronic effect, the nano-heterostructured TiO₂/C₃N₄ hybrid, which was well attached to Au NPs, could lead to new properties and could consequently promote CO preferential oxidation in the presence of H₂.