Electrochemically-synthesized tungstate nanocomposites γ-WO3/CuWO4 and γ-WO3/NiWO4 thin films with improved band gap and photoactivity for solar-driven photoelectrochemical water oxidation

Tao Zhu, Meng Nan Chong, Eng Seng Chan, Joey D. Ocon

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    Abstract

    The main aim of this study was to synthesize and characterise tungstate (WO3) nanocomposites with its metal-based nanostructures, such as copper (II) tungstate (CuWO4) and nickel tungsten oxide (NiWO4), as visible-light active thin film photoanodes for solar-driven photoelectrochemical (PEC) water oxidation. FE-SEM and AFM results showed that the bare as-deposited WO3 films were transformed into polycrystalline WO3 structure with highly agglomerated surfaces and roughness during the annealing-induced crystallisation process. XRD results suggested that the bare as-deposited WO3 films undergone phase transformation process from amorphous to the photoactive monoclinic-I (γ-WO3) at 550 °C. XPS results indicated the existence of WO42−, Ni2+ and Cu2+ ions at 35.58 eV, 856 eV and 932.4 eV, respectively. Through the formation of WO3 nanocomposites, the energy band gap was effectively lowered from 2.7 eV (γ-WO3) → 2.3 eV (γ-WO3/CuWO4) → 2.1 eV (γ-WO3/NiWO4) as estimated from the UV–Vis spectra. Finally, the corresponding photoactivity of WO3 nanocomposites was estimated by measuring the photocurrent density and γ-WO3/NiWO4 nanocomposite structure was found to give the highest photocurrent density of 400 μA/cm2 at 1.5 V vs Ag/AgCl (4 M KCl).

    Original languageEnglish
    Pages (from-to)90-97
    Number of pages8
    JournalJournal of Alloys and Compounds
    Volume762
    DOIs
    Publication statusPublished - 25 Sep 2018

    Keywords

    • Cathodic electrodeposition
    • Photoelectrocatalyst
    • Photoelectrochemical water splitting
    • Solar hydrogen fuel
    • Tungsten trioxide

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