Micro/nano-bubble assisted synthesis of Au/TiO2@CNTs composite photocatalyst for photocatalytic degradation of gaseous styrene and its enhanced catalytic mechanism

Abstract

A facile micro/nano-bubble method was firstly applied to synthesize an Au/TiO₂@CNT composite photocatalyst for photocatalytic degradation of gaseous styrene. The morphologies, structures and compositions of the photocatalysts were investigated by using a series of analytical techniques (scanning and transmission electron microscopy, FT-IR spectroscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy). The micro/nano-bubbles can effectively facilitate the reaction of Au and TiO₂ NPs decorated onto CNTs, forming a stable ternary composite structure. The photocatalytic performance of Au/TiO₂@CNTs was investigated by the methodology of central composite design (CCD) in response surface methodology (RSM). The photocatalytic degradation and mineralization of styrene over Au/TiO₂@CNTs drastically increased with the rise of reaction temperature due to the formation of a compact structure. The analysis of EPR, UV-vis DRS, electrochemical properties and TPD-O₂ further revealed the enhanced photocatalytic mechanism of Au/TiO₂@CNTs. The further identification of free radicals showed that the photocatalytic degradation and mineralization of styrene were closely related to oxidative radicals such as hydroxyl radicals and superoxide radicals, which were mainly attributed to the synergistic effects of Au NPs and CNTs to enhance the photocatalytic activity. This work will provide a new insight into designing photocatalysts with high photocatalytic performance and stability for the degradation of hazardous VOCs.