Enhancement of photocatalytic NO oxidation by Ag-sulfide on TiO₂ mixed with Na-ZSM-5

Enhancing NO oxidation performance is pivotal for integrating photocatalysts with wet scrubbers in continuous flow systems. Despite the recent development of various catalysts, such as MOFs, our goal was to simplify the composition by using photocatalyst + zeolite catalyst, bringing us closer to a catalyst that can be practically applied. In this study, we have utilized Ag₂S doping and Na-ZSM-5 mixing to improve the photocatalytic NO oxidation performance. Results showed that Ag₂S doping improved visible light absorbance and NO oxidation, despite the observed fluctuations in NO conversion being attributable to mass transfer limitations. Mixing with Na-ZSM-5 compensated for the mass transfer limitations and improved its average NO conversion from 19 to 34%. The Na-ZSM-5 increased the NO adsorption capacity considerably to 0.67 mmol g⁻¹, which reduced the fluctuations in the catalytic performance; subsequently, the diffusion of NO led to its oxidation. Detailed analyses using NO-TPD and DRIFTS further elucidated these improvements, highlighting the significance of optimizing both oxidation reaction and mass transfer rates in the photocatalytic process. We believed that the composite of Ag₂S-TiO₂ + Na-ZSM-5 could simplify the ways to improve the photocatalytic NO oxidation performance and make it closer to practical applications.