Enhanced photocatalytic removal of indoor formaldehyde by ternary heterogeneous BiOCl/TiO2/sepiolite composite under solar and visible light

Abstract

Mineral-based photocatalyst is a promising alternative to eliminate the volatile organic compounds (VOCs) air pollutants because of its low-cost and environmental-friendly merits. Herein, BiOCl/TiO2/sepiolite ternary heterogeneous photocatalyst was synthesized through a facile hydrolysis-precipitation method combining with the calcination crystallization procedure. The gaseous formaldehyde (HCHO) was employed as target pollutant to evaluate the photocatalytic activity of as-synthesized samples. The results indicated that BiOCl/TiO2/sepiolite composite performed much significantly higher adsorption and decomposition capacity for HCHO than pure TiO2, BiOCl and TiO2/BiOCl under solar and visible light. Based on the characterizations and density function theory (DFT) simulation results, the enhanced photocatalytic activity was mainly attributed to the synergistic effect between TiO2/BiOCl and sepiolite through the formation of ternary heterojunction. Such structure could lead to the higher adsorption capacity which can provide more reactive sites, and stronger light response ability as well as faster separation efficiency of photoinduced carriers forming more active radicals during the degradation process. Radical scavenger tests and ESR results indicated that photogenerated holes was the main active species in the reaction system. Overall, this study provides an insight into the design and synthesis of environment-friendly and high-effective heterogeneous composite for practical indoor formaldehyde removal.