Improved photocatalytic oxidation performance of gaseous acetaldehyde by ternary g-C3N4/Ag-TiO2 composites under visible light

Abstract

In the process of photocatalytic oxidation (PCO), titanium dioxide (TiO2) shows excellent capabilities. However, when TiO2 is used to remove volatile organic compounds (VOCs), there are some drawbacks including weak adsorption of gaseous contaminants, insufficient utilization of sunlight, and rapid recombination of photogenerated carriers. Herein, a TiO2-based ternary heterogeneous photocatalyst, g-C3N4/Ag-TiO2, was successfully fabricated to photodegrade gaseous acetaldehyde (one of the representatives of oxygenated VOCs) under visible light. Among the various samples, the g-C3N4/50 wt% Ag-TiO2 exhibited an excellent photocatalytic activity, which was 5.8 times of bare TiO2. The mineralization efficiency of acetaldehyde was also increased by 3.7 times compared to bare TiO2. The substantial improvement in the PCO performance of the ternary system can be associated with the good adsorption to acetaldehyde gas and light-harvesting capability, as well as improved charge separation process. The application of Langmuir-Hinshelwood kinetic model suggested that relative humidity played a significant role in the VOCs degradation. Also, the photodegradation of gaseous acetaldehyde primarily occurred on the catalysts surface. Based on several characterizations, i.e., UV–vis spectroscopy, photoluminescence spectrum, photocurrent spectroscopy and electron spin-resonance test, a suitable degradation mechanism is proposed. This study provides a novel ternary photocatalyst with improved photocatalytic performance and stability, which can be used for the low-concentration VOCs abatement in the indoor environment.