Investigating the role of Pd-coated TiO2@g-C3N4 heterojunctions in enhancing photocatalytic NO removal

Abstract

Heterostructure photocatalysts have emerged as a promising solution for efficiently removing air pollutants, leveraging their synergistic properties for enhanced photocatalytic activity. In this study, Pd/TiO₂@g-C₃N₄ heterojunction composites were synthesized via a wet impregnation method, integrating the surface plasmon resonance (SPR) effect of palladium nanoparticles (Pd NPs) to enhance visible-light photocatalysis. The Pd NPs, with an average particle size of 7.2 nm, were uniformly distributed on the TiO₂@g-C₃N₄ surface with minimal aggregation, ensuring optimal interaction within the composite. Under solar and visible-light irradiation, the 5 % Pd/TiO₂@g-C₃N₄ composites exhibited outstanding air pollutant oxidation efficiencies of 77.1 % and 67.2 %, respectively, while maintaining high stability over five recycling cycles with minimal formation of toxic byproducts. The enhanced performance was attributed to improved light absorption, narrowed bandgap, and efficient S-scheme charge transfer, with Pd NPs functioning as electron sinks to promote the generation of reactive oxygen species via the reduction process while suppressing electron–hole recombination. Mechanistic studies, supported by band structure analysis, trapping experiments, and EPR spectroscopy, revealed that photogenerated holes in TiO₂ dominate the oxidation process, while Pd facilitates charge separation and redox reactions. These results underscore the potential of SPR-enhanced heterojunction systems as robust and sustainable photocatalysts for environmental remediation.