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Energy, Environmental, and Catalysis Applications
WO3/BiVO4 Type-II Heterojunction Arrays Decorated with Oxygendeficient ZnO Passivation Layer: a Highly Efficient and Stable Photoanode Zizai Ma, Kai Song, Lin Wang, Fengmei Gao, Bin Tang, Huilin Hou, and Weiyou Yang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b18261 • Publication Date (Web): 18 Dec 2018 Downloaded from http://pubs.acs.org on December 20, 2018
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ACS Applied Materials & Interfaces
WO3/BiVO4 Type-II Heterojunction Arrays Decorated with Oxygen-deficient ZnO Passivation Layer: a Highly Efficient and Stable Photoanode Zizai Ma,†, ‡ Kai Song,† Lin Wang,‡ Fengmei Gao,‡ Bin Tang,*,† Huilin Hou,*,‡ and Weiyou Yang*,‡ † Research
Institute of Surface Engineering, Taiyuan University of Technology, Taiyuan, 030024, P.R. China.
‡
Institute of Materials, Ningbo University of Technology, Ningbo, 315211, P.R. China.
KEYWORDS: WO3/BiVO4, type-II heterojunction, passivation layer, nanoplate arrays, photoelectrochemistry
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ABSTRACT: In present work, we report a ternary WO3/BiVO4/ZnO photoanode with boosted PEC efficiency and stability towards highly efficient water splitting. The type-II WO3/BiVO4 heterojunction arrays are firstly prepared by hydrothermal growth of WO3 nanoplate arrays onto the substrates of fluorine-doped tin oxide (FTO) coated glasses, followed by spin-coating of BiVO4 layers onto the WO3 nanoplate surfaces. After that, thin ZnO layers are further introduced onto the WO3/BiVO4 heterojunction arrays via atomic layer deposition (ALD), leading to the construction of ternary WO3/BiVO4/ZnO photoanodes. It is verified that the ZnO thin layer in WO3/BiVO4/ZnO photoanode contains abundant oxygen vacancies, which could be acted as an effective passivation layer to enhance the charge separation and surface water oxidation kinetics of photogenerated carriers. The as-prepared WO3/BiVO4/ZnO photoanode produces a photocurrent of 2.96 mA cm-2 under simulated sunlight with an incident photon-to-current conversion efficiency (IPCE) of ∼72.8 % at 380 nm at a potential of 1.23 V vs. RHE without cocatalysts, both of which are comparable to the state-of-art WO3/BiVO4 counterparts. Moreover, the photocurrent of WO3/BiVO4/ZnO photoanode shows only 9 % decay after 6 h, suggesting its high photoelectrochemical (PEC) stability.
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ACS Applied Materials & Interfaces
INTRODUCTION The prompt growing need for clean energy to release our dependence on fossil fuel has motivated
the
scientific
community
to
harvest
the
solar
energy.1-2
Typically,
photoelectrochemical (PEC) water splitting into hydrogen driven by solar light has attracted worldwide attention as one of the most attractive and sustainable solution.3-6 Such PEC water splitting process relies fundamentally on the development of stable, economical, and efficient photoanodes. Among the semiconductor photoanode family, the earth-abundant metal oxides such as TiO2,7-8 WO3,9 Fe2O310 and BiVO411-12 are explored as the popular candidates. Particularly, WO3 and BiVO4 are recognized as the attractive and promising photoanode materials, owing to their physical and chemical stability, low cost with desired narrow band gaps.12-15 However, WO3 possesses a weak visible light response (
