title: M-Au/TiO2 (M = Ag, Pd, and Pt) nanophotocatalyst for overall solar water splitting: role of interfaces.
abstract: M-Au/TiO2 (M = Ag, Pd, Pt) composites were prepared through a facile one-pot photodeposition synthesis and evaluated for solar water splitting (SWS) with and without a sacrificial agent. The M-Au combination exhibits a dominant role in augmenting the H2 generation activity by forming a bi-metallic system. Degussa P25 was used as a TiO2 substrate to photodeposit Au followed by Au + M (M = Ag/Pd/Pt). The SWS activity of the M-Au/TiO2 was determined through photocatalytic H2 production in the presence of methanol as a sacrificial agent under one sun conditions with an AM1.5 filter. The highest H2 yield was observed for Pt0.5-Au1/TiO2 and was around 1.3 ± 0.07 mmol h(-1) g(-1), with an apparent quantum yield (AQY) of 6.4%. Pt0.5-Au1/TiO2 also demonstrated the same activity for 25 cycles of five hours each for 125 h. Critically, the same Pt0.5-Au1/TiO2 catalyst was active in overall SWS (OSWS) without any sacrificial agent, with an AQY = 0.8%. The amount of Au and/or Pt was varied to obtain the optimum composition and it was found that the Pt0.5-Au1/TiO2 composition exhibits the best activity. Detailed characterization by physico-chemical, spectral and microscopy measurements was carried out to obtain an in-depth understanding of the origin of the photocatalytic activity of Pt0.5-Au1/TiO2. These in-depth studies show that gold interacts predominantly with oxygen vacancies present on titania surfaces, and Pt preferentially interacts with gold for an effective electron-hole pair separation at Pt-Au interfaces and electron storage in metal particles. The Pt in Pt0.5-Au1/TiO2 is electronically and catalytically different from the Pt in Pt/TiO2 and it is predicted that the former suppresses the oxygen reduction reaction.
authors.affiliation: Catalysis Division, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India. cs.gopinath@ncl.res.in.
authors.forename: Ambrose A
authors.initials: AA
authors.lastname: Melvin
authors.forename: Kavya
authors.initials: K
authors.lastname: Illath
authors.forename: Tanmay
authors.initials: T
authors.lastname: Das
authors.forename: Thirumalaiswamy
authors.initials: T
authors.lastname: Raja
authors.forename: Somnath
authors.initials: S
authors.lastname: Bhattacharyya
authors.forename: Chinnakonda S
authors.initials: CS
authors.lastname: Gopinath