Site-Selective Deposition of Ordered Intermetallic PtPb Nanoparticle Co-Catalysts on WO3 Surfaces to Enhance Photocatalytic Activity

1.      Introduction

  Photocatalytic decomposition of organic pollutants is one of the promising method for environmental purification. Most of the researchers focused on efficient decomposition of environmental organic contaminants under visible light irradiation or indoor fluorescent light.¹ Oxide-supported metal catalysts are widely acknowledged as important catalysts that are related to versatile key in photochromism, chemical sensing and photocatalytic activity. Tungsten trioxide (WO₃) acts as a ideal visible light photocatalyst owing to its small band gap energy (2.4-2.8 eV) and high oxidation power of vanlence band holes. But, WO₃ exhibits low photocatalytic activity due its high recombination rate of photoexcited electrons and holes. In order to suppress the recombination of photoexcited carriers and significantly increase the photocatalytic efficiency, most research has focused to prepare WO₃ doping constituent or WO₃ composites.^2,3 In the present study, we have synthesized PtPb/WO₃ and PtAu/WO₃ alloy catalysts, demonstrated to exhibit the efficiency for the decompostion of organic pollutants under visible light irradiation.

2.      Experimental

    A simple one-pot synthesis approach to obtain WO₃ supported PtAu catalyst is as follows. In the synthesis, 0.5 g of WO₃ was suspended in 15 mL of anhyrous methanol for 15 min in a two neck round bottom flask. Pt (0.0075 g) and Au (0.0045 g) precursors were dissolved in 15 mL anhydrous methanol in the shielded vial uder Ar atmosphere and transferred to the suspensions. Then, the solution was stirred for 30 min to yield  homogeneous color soluion. Required amount of NaBH₄ in mehtanol was injected into the suspensions. The product were washed and centrifuged with anhydrous methanol for three times and dried under vacuum. Similar procedure was followed to synthesis the PtPb/WO₃ catalyst.

3.      Results and Discussion

  Figure 1 shows the TEM images of (a) Pt/WO₃ (b) PtPb/WO₃ and (c) PtAu/WO₃ photocatalysts. Pt and PtPb and PtAu NPs are showed monodispersity and homogeneity on the WO₃ supports. The average particle size of the three catalysts can be ranked as PtPb/WO₃~PtAu/WO₃ > Pt/WO₃. The TEM results show that the addition of Pb and Au increases the size of NPs. Figure 2 depicts that the CO₂ formation profile over different photocatalysts under visible light irradiation time. PtPb/WO₃ photocatalyst (1 wt %) shows the higher rate of CO₂formation over other photocatalysts. The details about the characterization and photocatalytic activity of catalysts would be discussed in the presentation.

4. References

1. M.R. Hoffmann, S.T. Martin, W. Choi and D.W. Bahnemann, Chem. Rev., 95, 69, (1995).

2. R. Abe, H. Takami, N. Murakami and B. Otani, J. Am. Chem. Soc., 130, 7780, (2008).

3. M. Miyauchi, Phys. Chem. Chem. Phys., 10, 6258, (2008).