Temperature-boosted photocatalytic H-2 production and charge transfer kinetics on TiO2 under UV and visible light

Abstract

This study investigates the effect of reaction temperature (298-353 K) on photocatalytic H-2 production in bare and platinized TiO2 (Pt/TiO2) suspensions containing various organic hole scavengers (EDTA, methanol, and formic acid) under UV (lambda> 320 nm) and visible light (lambda > 420 nm for ligand-to-metal charge transfer). H-2 production rates are enhanced similar to 7.8- and similar to 2.5-fold in TiO2 and Pt/TiO2 suspensions, respectively, with EDTA under UV by simply elevating the reaction temperature from 298 K to 323 K (Delta T = 25 degrees C). Such a temperature-boosted increase in H-2 production is always observed, regardless of the TiO2 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