Enhancing photocatalytic H2 production and dye degradation: Comparative analysis of gold reduction techniques on Au/TiO2 nanocomposites

This study compares the impact of two reduction techniques, thermal reduction (TR) and photocatalytic reduction (PR), on Au/TiO2 photocatalysts synthesized using the deposition-precipitation with urea method. Characterization methods, including temperature-programmed reduction, UV-Vis diffuse reflectance spectroscopy, electrochemical assessments (open-circuit potential and linear sweep voltammetry), and transmission electron microscopy, were employed. The 2-h. PR treatment yielded a highly effective photocatalyst (0.5Au-PR2), with 93.6% of gold nanoparticles below 4 nm, outperforming the TR counterpart (76.8%). All Au-loaded samples exhibited an absorption band between 400 and 800 nm, indicating the localized surface plasmon resonance (LSPR) effect. Interestingly, the TR catalyst had a broader LSPR band than the PR catalyst. Additionally, the 0.5Au-PR2 sample showed higher photocurrent and superior photocatalytic activity in the degradation of methyl orange and hydrogen production, which is attributed to its smaller particle size (2.9 nm) and weaker metal-support interaction. This smaller particle size emphasizes the crucial role of reduction techniques in tailoring Au/TiO2 photocatalysts for enhanced performance.