Photocatalytic decomposition of indoor ozone motivated by the white-light-emitting diode

Abstract

TiO2 photocatalysis driven by ultraviolet (UV) light has been utilized to remove harmful indoor ozone in many previous studies. However, UV lamp is energy-consuming, and UV radiation has been classified as a carcinogen. For sustainability and health’s sake, we investigated the photocatalytic degradation of ozone driven by the white-light-emitting diode in the present study. Five different materials including nitrogen-doped TiO2 (TiO2-N), TiO2 hydrogenated at 300 and 350 °C (TiO2-H300 and TiO2-H350), P25 and Merck TiO2 were used as photocatalysts in the experiments. We also examined the effects of relative humidity (RH35-80%), ozone concentration (50–250 ppb) and air flow rate (2–8 Lpm) on the ozone removal efficiency. Because H2O could increase electron–hole recombination by inducing surface structural bending, the ozone removal efficiency of all the photocatalysts decreased with the increase in RH. Among the five photocatalysts, the nanotubular structure of TiO2-N created the largest surface area for the adsorption of ozone, and the nitrogen doping enhanced the visible-light absorbance. Therefore, TiO2-N exhibited the highest apparent reaction rate of ozone decomposition. However, the nanotubular structure of TiO2-N also generated a mass transfer barrier that obstructed the removal of ozone. Fortunately, there was no significant mass transfer limitation in the granular photocatalysts (P25 TiO2, TiO2-H300 and TiO2-H350). This study provides practical data for the implication of visible-light-driven photocatalytic degradation of ozone.