Photocatalytic Decomposition of Various Organic Compounds over WO3 Supported Ordered Intermetallic Ptpb Co-Catalyst
Authors: Gunji Takao , Tanabe Toyokazu , Kaneko Shingo , Matsumoto Futoshi 
Published: February 2020

In recent years, photocatalysis semiconductor, such as TiO2, WO3, are focused as environment remediation, H2 evolution, water splitting and CO2 reduction. Photocatalysts that respond in the visible light irradiation are very useful because they decompose  harmful organic compounds such as acetic acid and formaldehyde in a room light or sunlight.  Specifically, WO3 is attracting increasing interest because of visible light-responsive and are deeper valence band of hole. However, WO3 by itself cannot be used as a photocatalyst. The conduction band level of WO3 (+0.5 V vs. NHE) is slightly negative compared with the potential for the multi-electron reduction of oxygen (O2/H2O2 = 0.68 V vs. NHE). Therefore in order to use WO3 as a photocatalyst to decompose organic compounds, WO3 photocatalyst required a co-catalyst to facilitate oxygen reduction reaction on photocatalyst. Abe and co-workers reported that 1 wt. % Pt-loading WO3 (Pt NPs/WO3) effectively decomposed organic compound under visible and ultraviolet light in oxygen-rich atmosphere and its apparent quantum efficiency (QE) is ca 10%.1 This result was indicating that photocatalytic activity had been realized multi-electron reactions on Pt NPs that Pt as co-catalyst was facilitating oxygen reduction reaction on WO3. On the other hand, we previously reported that ordered interemetallic PtPb NPs efficiently electrocatalyzed oxidation of formic acid, methanol and ethanol.2 In our recent study, ordered intermetallic PtPb NPs on TiO2 was electrochemically accelerated the oxygen reduction reaction (ORR) in acidic media.3 In addition, We reported that H2PtCl6∙6H2O and Pb(CH3COO)2 were co-reduced using sodium borohydride to precipitate PtPb NPs (average particles size: 9.5 nm) over WO3 support (PtPb NPs/WO3). PtPb NPs/WO3 showed a substantial photocatalytic activity towards decomposition of acetic acid in aqueous solution.4  However, photocatalytic activity had not been enough because particle size was not controlled in this method, and detail of reaction mechanism was undisclosed. Here in, in order to increase photocatalytic activity towards decomposition of various organic compounds, we report intermetallic PtPb NPs as co-catalyst ofhotocatalysis. PtPb/WO3 has been synthesized via photodeposition and polyol method to control the particle size. The product was compared to the pure WO3 and Pt NPs/WO3towards decomposition of various organic compounds. In addition, we considerd the effectiveness of co-catalysts during decomposition of organic compounds.

(1) R. Abe, H. Takami,N. Murakami and B. Ohtani, J. Am. Chem. Soc., 130, 7780-7781(2008).

(2) T. Gunji and F. Matsumoto, et al, J. Power Sources, 273, 990-998 (2015) .

(3) T. Gunji, G. Saravanan, T. Tanabe, T. Tsuda, M. Miyauchi, G. Kobayashi, H. Abe and F. Matsumoto, Catal. Sci. Technol., 4, 1436-1445 (2014).

(4) Takao Gunji, Takashi Tsuda, Arockiam John Jeevagan, Masanari Hashimoto, Toyokazu Tanabe, Shingo Kaneko, Masahiro Miyauchi Govindachetty Saravanan, Hideki Abe and Futoshi Matsumoto, Catalysis Communications, 56, 96-100 (2014).