Enhanced photocatalytic performance at a Au/N–TiO2 hollow nanowire array by a combination of light scattering and reduced recombination

Abstract

We demonstrate one-step gold nanoparticle (AuNP) coating and the surface nitridation of TiO₂ nanowires (TiO₂-NWs) to amplify visible-light photon reflection. The surface nitridation of TiO₂-NW arrays maximizes the anchoring of AuNPs, and the subsequent reduction of the band gap energy from 3.26 eV to 2.69 eV affords visible-light activity. The finite-difference time-domain (FDTD) simulation method clearly exhibits the enhancement in the strengths of localized electric fields between AuNPs and the nanowires, which significantly improves the photocatalytic (PC) performance. Both nitridation and AuNP decoration of TiO₂-NWs result in beneficial effects of high (e⁻/h⁺) pair separation through healing of the oxygen vacancies. The combined effect of harvesting visible-light photons and reducing recombination in Au/N-doped TiO₂-NWs promotes the photocatalytic activity towards degradation of methyl orange to an unprecedented level, ∼4 fold (1.1 × 10⁻² min) more than does TiO₂-NWs (2.9 × 10⁻³ min⁻¹). The proposed AuNP decoration of nitridated TiO₂-NW surfaces can be applied to a wide range of n-type metal oxides for photoanodes in photocatalytic applications.