This study reports a noble metal-free robust inorganic photocatalyst for H 2 O 2 synthesis via two-electron oxygen reduction reaction (ORR). Antimony-doped tin oxide nanorods were heteroepitaxially grown from rutile TiO 2 seed crystals with an orientation of (001) ATO //(001) TiO2 (ATOÀ NR//TiO 2 ,//denotes heteroepitaxial junction) by a hydrothermal method. UV-light irradiation of ATOÀ NR//TiO 2 particles stably and continuously produces H 2 O 2 from aerated aqueous solution of ethanol. Electrochemical measurements using rotating electrodes show that Sb-doping into SnO 2 greatly enhances the electrocatalytic activity for two-electron ORR. The striking photocatalytic activity of ATOÀ NR//TiO 2 stems from the effective charge separation, electrocatalytic activity for two-electron ORR, low catalytic activity for H 2 O 2 decomposition, and extraordinary robustness.

The establishment of technology for rapid and complete removal and mineralization of harmful phenolic compounds from water is of great importance for environmental conservation. Visible-light irradiation (λ > 430 nm, light intensity integrated from 420 to 485 nm = 6.0 mW cm) of Au nanoparticle (NP)-loaded TiO (Au/TiO) in dilute aqueous solutions of bisphenol A (BPA) and p-cresol (PC) causes degradation of the phenols. The addition of trimethylstearylammonium chloride (CTAC) enhances the adsorption of BPA on Au/TiO to greatly increase the rate of reaction. Consequently, 10 μM phenols are completely removed from the solutions within 2.5 h irradiation, and prolonging irradiation time to 24 h quantitatively oxidizes BPA to CO. Dynamic light scattering ζ-potential measurements indicate that a CTAC bilayer or admicelle is formed on the Au/TiO particle surface at CTAC concentration >50 μM. The action spectrum for reaction shows that this reaction is driven by the Au NP localized surface plasmon resonance excitation-induced interfacial electron transfer from Au to TiO. We propose a possible reaction scheme on the basis of the experimental results including intermediate analysis.

Au and Pt nanoparticle-loaded anatase TiO2 particles (Au/TiO2 and Pt/TiO2) were separately prepared by the deposition–precipitation method. Also, selective Pt photodeposition on the Au surface of Au/TiO2 yielded Au (core)–Pt (shell) bimetallic NP-loaded TiO2 particles. In Au (core)–Pt (shell)/TiO2, the mean Pt-shell thickness was controlled at an atomic layer level by irradiation time. The thermocatalytic activities of Au/TiO2, Pt/TiO2, and Au (core)–Pt (shell)/TiO2 for the decomposition of H2O2 were evaluated in the dark at 25 °C. Au (core)–Pt (shell)/TiO2 exhibits a much higher activity than that of Au/TiO2 and even Pt/TiO2 in spite of that Pt has the highest activity among the metals. The turnover frequency depends on the mean number of Pt layers, reaching a maximum of 1.1 × 106 around the monolayer. Density functional theory simulations were performed to analyze the potential-energy surfaces in metal-cluster-catalyzed H2O2 decomposition with Au50, Pt50, and Au14 (core)–Pt36 (shell) used as model metal clusters. The results explain the relative catalytic activities of Au/TiO2 ≪ Pt/TiO2 < Au@Pt/TiO2, further indicating the affinity of the metal clusters for oxygen atom produced in the course of reaction.

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