Influence of Pt loading on the Schottky barrier height and the photothermal activity of TiO₂/Pt catalysts

This study investigates the influence of platinum (Pt) loading on the photothermal NO₂ reduction activity of TiO₂/Pt catalysts, focussing on the relationship between Schottky barrier height (SBH) and catalytic performance. Noble metals such as Pt generate “hot electrons” under visible light due to their localised surface plasmon resonance (LSPR) properties. These electrons are injected into the TiO₂ conduction band, and the efficiency depends on the SBH at the TiO₂/Pt interface. Catalysts with different Pt loadings (0.5-2 wt%) were synthesised by wet impregnation and then extensively characterised using techniques such as XRD, TEM, SEM-EDS, XPS and UV-vis DR spectroscopy to evaluate their optical, electronic and structural properties. The results showed that higher Pt loading reduced the SBH from 0.42 eV for TiO₂/0.5%Pt to 0.16 eV for TiO₂/2%Pt. This reduction facilitates faster electron injection and minimises recombination, which increases the photothermal NO₂ reduction performance. The average size of Pt nanoparticles increased from 1.1 nm to 1.5 nm with increasing Pt content, but the morphology and crystallinity of TiO₂ remained stable. Catalytic tests showed that TiO₂ was inactive below 100 °C, while TiO₂/Pt catalysts enabled NO₂ reduction at temperatures as low as 30 °C under visible light. However, a higher SBH value reduced the activity due to increased electron–hole recombination at the TiO₂/Pt interface. The results confirm the multifunctionality of TiO₂/Pt catalysts and demonstrate their suitability for hybrid photothermal reaction systems for NO_x reduction at low temperatures. These results underline the crucial role of optimising Pt loading to balance SBH and improve catalytic performance in photothermal applications.