Operando Laboratory X-ray Absorption Spectroscopy and UV-Vis Study of Pt/TiO2 Photocatalysts during Photodeposition and Hydrogen Evolution Reactions

Photocatalytic hydrogen (H-2) production is a promising route for alternative energetics. Understanding structure-activity relationships is a crucial step towards the rational design of photocatalysts, which requires the application of operando spectroscopy under relevant working conditions. We performed an operando investigation on a catalytic system during the photodeposition of Pt on TiO2 and photostimulated H-2 production, using simultaneous laboratory X-ray absorption spectroscopy (XAS), UV-Vis spectroscopy, and mass spectrometry. XAS showed a progressive increase in Pt fluorescence for Pt deposited on TiO2 for over an hour, which is correlated with the signal of the produced H-2. The final Pt/TiO2 catalyst contained Pt(0) particles. The electronic features corresponding to the Pt4+ species in the UV-Vis spectrum of the solution disappear as soon as UV radiation is applied in the presence of formic acid, which acts as a hole scavenger, resulting in the presence of Pt(0) particles in solution.