Pt/TiO2 Prepared by Mechanochemistry Boosts Photocatalytic Production of Hydrogen

Ball milling enables the rapid synthesis of a Pt/TiO₂ photocatalyst with atomically dispersed Pt, outperforming a conventional Pt-cluster catalyst (1.3× higher H₂ evolution from ethanol). Enhanced activity is attributed to single-atom stabilization and suppressed surface restructuring, promoting efficient charge separation via Schottky barrier modulation.

Abstract

A series of Pt-decorated TiO₂ photocatalysts was synthesized via mechanochemical methods, varying Pt precursors (K₂PtCl₆, H₂PtCl₆, PtO₂, Pt(NH₃)₄(NO₃)₂, Pt(acac)₂, and PtCl₂), Pt loadings, and milling conditions (time, energy, and ball-to-powder ratio). Hydrogen photoproduction was evaluated under dynamic conditions using gas-phase ethanol–water mixtures and UV light. The optimal catalyst, prepared with K₂PtCl₆ at 0.33 wt.% Pt, exhibited the highest hydrogen production rate (7.4 mmol H₂ h⁻¹ g_cat ⁻¹). Synthesis optimization via a Taguchi design of experiments identified low milling time, energy, and ball-to-powder ratio as key factors. Compared to a conventional Pt/TiO₂ catalyst prepared by incipient wetness impregnation, the best ball-milled sample showed 1.3 times higher hydrogen production and 1.2 times faster stabilization. Advanced characterization (HAADF-STEM) revealed isolated Pt atoms in the ball-milled catalyst, in contrast to small clusters in the reference. Post-reaction analysis showed nanoparticle growth in both samples, but only the conventional sample developed fully formed nanoparticles (2.0 ± 0.8 nm). XPS detected a significant increase in surface K in the conventional catalyst due to a resurfacing effect. The superior performance of the ball-milled sample is attributed to the stabilization of Pt single atoms and suppression of surface K restructuring, enhancing charge separation via modulation of the Schottky barrier.

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