462617 The Fabrication of Cu2o/g-C3N4/WS2 Triple-Layered Photocathode for Photoelectrochemical Hydrogen Evolution

Tuesday, November 15, 2016: 2:20 PM
Golden Gate 8 (Hilton San Francisco Union Square)
Xintian Xu, Yuanzhi Zhu, Xiaobin Fan, Guoliang Zhang and Wenchao Peng, School of Chemical Engineering & Technology, Tianjin University, Tianjin, China

 The Fabrication of Cu2O/g-C3N4/WS2 Triple-layered Photocathode for Photoelectrochemical Hydrogen Evolution

Xintian Xu, Yuanzhi Zhu, Xiaobin Fan, Guoliang Zhang, Wenchao Peng*

School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, China.

wenchao.peng@tju.edu.cn

Hydrogen is being vigorously pursued as a future energy carrier due to the fossil energy depletion. Photoelectrochemical (PEC) water splitting is an emerging hydrogen production technology by utilizing the solar light. This technology integrates in the same device both solar energy collection and water electrolysis. Both photo-active semiconductor and catalysts for hydrogen evolution reaction (HER) are necessary in this device. Cu2O is a direct P-type semiconductor with a narrow band gap (~2.0 eV), which can be activated by the visible light. Moreover, Cu is a kind of earth abundant element, and the synthesis of Cu2O is facile. Cu2O is therefore one of the most promising low-cost photoactive semiconductor reported until now. However, the activity of bare Cu2O is still poor, and it is not stable towards chemical oxidants and light corrosion. Combing with other semiconductors (e.g. TiO2, ZnO) could improve the activity and stability of Cu2O effectively.

As we know, Pt and other precious metals are the most efficient catalysts for hydrogen evolution reaction (HER). However, these metals are rare and expensive to apply. Transition-metal dichalcogenides (TMDs), such as Molybdenum disulfide (MoS2), tungsten disulphide (WS2), are emerging HER catalysts that could be used as a substitute for noble metals in HER.

In this study, a novel Cu2O/g-C3N4/WS2 triple-layered photocathode was designed for the PEC hydrogen evolution. Cu2O was electrodeposited on the FTO glass as the active layer for the light harvesting. A metal-free g-C3N4 was exfoliated and covered on the surface of Cu2O as protection layer. G-C3N4 could also form p-n junction with Cu2O to increase the activity. 1T-WS2was obtained by lithium intercalation and used as HER catalyst for the further modification of the photocathode.

The obtained photocathode was then used for PEC HER test in the Na2SO4/H2SO4 solution (λ≥420nm, 100 mW/cm2). With the irradiation, electron-hole pair will be generated in the p-type Cu2O, and the excited electron could be then extracted through the g-C3N4 protective layer to produce hydrogen on the WS2. The efficient extraction of excited electrons by this triple-layered photocathode leads to photocurrents of up to -6 mA/cm-2 at -0.4 V versus RHE (pH 6.0). The corresponding overpotential is -0.23 V (versus RHE) for the H2 evolution. In sharp contrast, nearly no H2 evolution happened under dark conditions. This photocathode is facile to synthesis and has great potential for developing low-cost PEC water-splitting device.


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