Enhanced photocatalytic hydrogen production by loading histidine on TiO₂

Although TiO₂ exhibits excellent photocatalytic properties, its application has been limited owing to rapid e⁻/h⁺ recombination. Therefore, TiO₂ has failed to reach the desired effect in terms of efficient photocatalytic hydrogen production. In this study, a range of titanium dioxide catalysts loaded with histidine (His) were prepared by an easy dipping method, viz. by treating TiO₂ in His aqueous solutions with different concentrations at ambient temperature. Photocatalytic hydrogen evolution by splitting water was performed on His-modified TiO₂ under 300-W Xe irradiation. His-loaded TiO₂ catalysts exhibited improved photocatalytic performance compared with pristine TiO₂; TiO₂ treated in 1 × 10⁻³ mol · L⁻¹ His showed the highest photocatalytic H₂ evolution activity (4.77 µmol g⁻¹ h⁻¹ gm⁻²), which was 3.77 times higher than that of pure TiO₂. Infrared and XPS analysis showed that His was successfully combined to the TiO₂ surface by hydrogen bonding, constructing a fast channel for interfacial charge transfer. In the photocatalytic process, the photogenerated holes could migrate from the valence band of TiO₂ to the highest occupied molecular orbital of His, which reduced the recombination rate of photogenerated e⁻/h⁺ pairs, consequently, improved H₂ production efficiency. Importantly, the composite catalyst exhibited no decline in photocatalytic activity over 30 h of operation. This research provides an alternative approach for creating high-efficiency photocatalysts for H₂ production.