Size-Controlled Synthesis of Pt Particles on TiO2 Surface: Physicochemical Characteristic and Photocatalytic Activity

Zielińska-Jurek Zielińska-Jurek,Kowalska Kowalska,Wysocka Wysocka,Janczarek Janczarek,Wei Wei

doi:10.3390/catal9110940

Abstract

Different TiO2 photocatalysts, i.e., commercial samples (ST-01 and P25 with minority of rutile phase), nanotubes, well-crystallized faceted particles of decahedral shape and mesoporous spheres, were used as supports for deposition of Pt nanoparticles (NPs). Size-controlled Pt NPs embedded in TiO2 were successfully prepared by microemulsion and wet-impregnation methods. Obtained photocatalysts were characterized using XRD, TEM, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) specific surface area, DR/UV-vis and action spectrum analysis. The effect of deposition method, amount of Pt precursor and TiO2 properties on size, distribution, and chemical states of deposited Pt NPs were investigated. Finally, the correlations between the physicochemical properties and photocatalytic activities in oxidation and reduction reactions under UV and Vis light of different Pt-TiO2 photocatalysts were discussed. It was found that, regardless of preparation method, the photoactivity mainly depended on platinum and TiO2 morphology. In view of this, we claim that the tight control of NPs’ morphology allows us to design highly active materials with enhanced photocatalytic performance. Action spectrum analysis for the most active Pt-modified TiO2 sample showed that visible light-induced phenol oxidation is initiated by excitation of platinum surface plasmon, and photocatalytic activity analysis revealed that photoactivity depended strongly on morphology of the obtained Pt-modified TiO2 photocatalysts.

Highlights

The photocatalytic properties of titanium (IV) oxide are applied for degradation of emerging organic pollutants in the aqueous and gaseous phases [1,2,3,4], microorganisms [5], self-cleaning and anti-fogging surfaces [6]
It has been proposed that the enhanced photocatalytic activity is attributed to the fast separation of photogenerated charge carriers’, improved light absorption, high specific surface area as well as multi-porous structure of the photocatalyst
It was proposed that a porous structure provides more single sites and special passages for charge transport, which results in markedly enhanced photocatalytic activity

Summary

Introduction

The photocatalytic properties of titanium (IV) oxide are applied for degradation of emerging organic pollutants in the aqueous and gaseous phases [1,2,3,4], microorganisms [5], self-cleaning and anti-fogging surfaces [6]. It should be pointed that photocatalytic efficiency under UV irradiation depends strongly on the electron transfer from the excited semiconductor to metal particle deposited on its surface [20]. Xiong et al [21] deposited Pt NPs on TiO2 using photodeposition and chemical reduction methods. They found that photodeposition using H2 PtCl6 as a precursor contributed to smaller sizes of Pt NPs than chemical deposition using Pt(NH3 ) Cl2 as a platinum ions’ source [21]. Deposition of platinum onto commercial TiO2 P25 (Evonik) resulted in lower photocatalytic activity in phenol degradation [22]

Methods

Results

Discussion

Conclusion