RuO2/TiO2/Pt Ternary Photocatalysts with Epitaxial Heterojunction and Their Application in CO Oxidation

Coexisting oxidation and reduction cocatalysts play a significant role in the photocatalytic oxidation reaction. Here a surface modification method was used to synthesize the ternary photocatalyst RuO2/TiO2/Pt with RuO2 nanoclusters of ca. similar to 2 nm size. Further, thermal treatment was adopted to transform RuO2 nanoclusters into an epitaxial layer on the surface of TiO2 to form ep-RuO2/TiO2/Pt. XRD, TEM, and XPS were used to verify the formation of the RuO2 epitaxial layers on both rutile and anatase TiO2. The interfacial atom arrangement match between the RuO2 and TiO2 is suggested as the possible physical basis for the transformation process of RuO2 from nanopartides to epitaxial layers. The photocatalytic performance of RuO2/TiO2/Pt and ep-RuO2/TiO2/Pt was studied by photocatalytically oxidizing gaseous CO under the UV irradiation. The optimal RuO2 contents in the ep-RuO2/TiO2/Pt were 0.05, 0.1, and 0.02 wt % for P25, commercial anatase, and commercial rutile TiO2, respectively. In their optimal RuO2 contents, the photocatalytic activity of the ep-RuO2/TiO2/Pt for CO oxidation are ca. 2.6, 2.4, 1.7 times than that of their uncalcined ones and ca. 20, 15, 8 times that of their corresponding bare TiO2 for P25, anatase, and rutile, respectively. The formation of interfacial epitaxial RuO2 layers leads to more significant exposure of RuO2 (110) facets in the ep-RuO2/TiO2/Pt ternary photocatalyst, which plays an effective role in promoting photocatalytic CO oxidation.