Conformal BiVO4-Layer/WO3-Nanoplate-Array Heterojunction Photoanode Modified with Cobalt Phosphate Cocatalyst for
Xueliang Zhang1,2, Xin Wang1,2, Defa Wang1,2
1TJU-NIMS International Collaboration laboratory, Key Lab of Advanced Ceramics and Machining Technology (Ministry of Education), Tianjin Key Lab of Composite and Functional Materials, School of Materials Science and Engineering , Tianjin University , 92 Weijin Road , Tianjin 300072 , China.
Abstract:
Constructing semiconductor heterojunctions via surface/interface engineering is an effective way to enhance the charge carrier separation/transport ability and thus the photoelectrochemical (PEC) properties of a photoelectrode. Herein, we report a conformal BiVO4-layer/WO3-nanoplate-array heterojunction photoanode modified with cobalt phosphate (Co-Pi) as oxygen evolution cocatalyst (OEC) for significant enhancement in PEC performances. The BiVO4/WO3 nanocomposite is fabricated by coating a thin conformal BiVO4 layer on the surface of presynthesized WO3 nanoplate arrays (NPAs) via stepwise spin-coating, and the decoration of Co-Pi OEC is realized by photoassisted electrodeposition method. The optimized Co-Pi@BiVO4/WO3 heterojunction photoanode shows a maximum photocurrent of 1.8 mA/cm2 at 1.23 V vs RHE in a phosphate buffer electrolyte under an AM1.5G solar simulator, which is 5 and 12 times higher than those of bare WO3 and BiVO4 photoanode, respectively. Measurements of UV-vis absorption spectra, electrochemical impedance spectra (EIS) and photoluminescence (PL) spectra reveal that the enhanced PEC performances can be attributed to the increased charge carrier separation/transport benefited from the type II nature of BiVO4/WO3 heterojunction and the promoted water oxidation kinetics and photostability owing to the decoration of Co-Pi cocatalyst.
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