Abstract
Pt, as a common cocatalyst, has been widely used in photocatalytic H2 evolution. However, the specific role of Pt in photocatalytic H2 evolution has not been thoroughly studied. In this paper, by employing three Pt sources with different charges (positive, negative and neutral), we systematically studied the charge effect of Pt sources on photocatalytic H2 evolution via TiO2 catalyst. According to the results of Raman, X-ray photoelectron spectroscopy (XPS), recycle experiments and photocurrent characterizations, it was found that TiO2 would produce electropositive defects during photocatalytic H2 evolution, inevitably leading to the decline of H2 production activity. Thanks to the electrostatic interaction, the electronegative Pt source not only promoted charge separation, but preferential deposited on electropositive defects, which acted as the defect repair agent, and thus resulted in the increased photocatalytic stability. This work may provide a new perspective for enhancing photocatalytic stability of hydrogen production.
Highlights
Since Fujishima A and Honda K of the University of Tokyo first reported the phenomenon of photocatalytic H2 evolution in 1972, photocatalytic H2 evolution has gradually become a focus of academic research [1]
When three kinds of Pt were introduced into the system, i.e., positive charged Pt source PtCl4 (TiO2 -Pt4+ ), negative charged Pt source H2 PtCl6 (TiO2 -PtCl6 2− )
The photocatalytic H2 evolution activity of TiO2 –Pt0 was slightly lower than TiO2 -PtCl6 2−
Summary
Since Fujishima A and Honda K of the University of Tokyo first reported the phenomenon of photocatalytic H2 evolution in 1972, photocatalytic H2 evolution has gradually become a focus of academic research [1]. Recent studies considered that the decrease in activity is mainly due to the interaction of photo-generated electron-hole pairs with water and oxygen in the surrounding environment. The effects of Pt sources with different charges (positive, negative and neutral) on the reaction stability of TiO2 photocatalytic H2 evolution were investigated in details. It was found that the positive charged defects were generated on the TiO2 surface in the photocatalytic reaction, leading to the decreased stability. Considering that H2 PtCl6 is slightly negative charged, loaded Pt with H2 PtCl6 , can improve the photocatalytic H2 evolution activity of TiO2 catalyst, and act as the defect repair agent to improve the stability of TiO2. The possible scheme of H2 PtCl6 improving photostability of TiO2 was proposed
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