Preparation of Ordered Intermetallic PtBi co-Catalyst Nanoparticles/WO3 and its Photocatalytic Activity towards the Decomposition of Acetic Acid

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).