Modelling the photocatalytic oxidation of methane and other air pollutants for applications in ventilation systems

Samuel D. Tomlinson; Aliki Marina Tsopelakou; Tzia Ming Onn; Steven R. H. Barrett; Adam M. Boies; Shaun Fitzgerald

paper

Modelling the photocatalytic oxidation of methane and other air pollutants for applications in ventilation systems

arXiv:2605.23999

Abstract

Photocatalytic oxidation (PCO) is a promising strategy for indoor air purification and outdoor pollutant abatement, potentially offering treatment for climate- and health-relevant pollutants such as methane (CH $_{4}$ ), nitrogen oxides (NO $_{x}$ ) and volatile organic compounds (VOCs). In this work, we present experiments evaluating the PCO of CH $_{4}$ (2 to 10 ppm) under varying UV-C light intensities (4 to 59 W/m $^{2}$ ), using titanium dioxide (TiO $_{2}$ ) as the photocatalyst. At 2 ppm CH $_{4}$ , TiO $_{2}$ achieves a maximum conversion efficiency of 24.4% and a maximum apparent quantum yield of $0.013$ % over the tested UV-C light intensities, demonstrating activity at environmentally relevant concentrations. We develop a model to interpret the experimental results and assess the potential of PCO for ventilation applications. The model is validated against our CH $_{4}$ data and literature results for formaldehyde (HCHO) and NO $_{x}$ . While laboratory-scale configurations achieve high conversions (e.g., 24.4% for CH $_{4}$ ), ventilation-scale performance is predicted to be limited by thin concentration boundary layers and short residence times, with conversion efficiencies dropping to around $0.017$ %. Finally, we estimate the climate impact of CH $_{4}$ removal in terms of CO $_{2}$ e emission rates, demonstrating that TiO $_{2}$ -based PCO in ventilation applications can yield a net climate benefit (i.e., a net-negative CO $_{2}$ e emissions rate) when the modelled CO $_{2}$ e removal rate exceeds the emissions from catalyst material production and UV operation, particularly when pre-existing UV-C irradiation is leveraged.