Temperature-boosted photocatalytic H production and charge transfer kinetics on TiO under UV and visible light

This study investigates the effect of reaction temperature (298-353 K) on photocatalytic H 2 production in bare and platinized TiO 2 (Pt/TiO 2 ) suspensions containing various organic hole scavengers (EDTA, methanol, and formic acid) under UV ( λ > 320 nm) and visible light ( λ > 420 nm for ligand-to-metal charge transfer). H 2 production rates are enhanced ∼7.8- and ∼2.5-fold in TiO 2 and Pt/TiO 2 suspensions, respectively, with EDTA under UV by simply elevating the reaction temperature from 298 K to 323 K (Δ T = 25 °C). Such a temperature-boosted increase in H 2 production is always observed, regardless of the TiO 2 crystalline structure (anatase, rutile, and an anatase/rutile mixture), type of hole scavenger, and irradiation wavelength range. It is estimated that approximately 90% of incident photons are utilized in H 2 production, for which the activation energy is 25.5 kJ mol −1 . Detailed photoelectrochemical analyses show the positive relationship between reaction temperature and photocurrent generation, with charge carrier mobility and interfacial charge transfer improving at higher temperatures. Other possible factors, such as H 2 solubility and mass transport, play a limited role. H 2 production rates were enhanced ∼7.8- and ∼4.5-fold in TiO 2 and Pt/TiO 2 suspensions, respectively, with hole scavengers under UV by simply elevating the reaction temperature.