Enhancement of Photoelectrochemical Properties of BiVO₄ Layer Coated ZnO Nanodendrite Core-Shell Nanocomposites: Electronic Mechanism from X–ray Spectro-Microscopic Studies

Hsiao-Tsu Wang^1*, Kuan-Hung Chen¹, Wei Xuan Lin¹, Chin Wei Li¹, Shu Ang Teng¹, Jing Qi Fan¹, Tai Chen Wu¹, Jia Cheng Wang¹, Hung-Wei Shiu², Chih-Wen Pao², Jyh-Fu Lee², Jih-Jen Wu³, Takuji Ohigashi⁴, obuhiro Kosugi⁴, Way-Faung Pong¹

¹Department of Physics, Tamkang University, Tamsui, Taiwan
²National Synchrotron Radiation Research Center, Hsinchu, Taiwan
³Chemical Engineering, National Cheng Kung University, Tainan, Taiwan
⁴Institute for Molecular Science, Okazak, Japan

* Presenter:Hsiao-Tsu Wang, email:hsiaotsu0108@gmail.com

Synchrotron-based X-ray spectro- and microscopic techniques are used in the present study to understand the origin of enhancement of photoelectrochemical (PEC) properties with nanocomposite BiVO₄ (BVO) coated on ZnO nanodendrites, named as BVO/ZnO. This high PEC nanodendrites core-shell BVO/ZnO heterojunction is successfully grown and well-characterized for morphological and structural details. The strongly charge transfer (CT) behavior from the V 3d (at shell-BVO) to Zn 4s/p (core-ZnO) in core-shell BVO/ZnO with the high number of O 2p unpair derived states at the interface is caused by the increasing the defects at the interface to construct interfacial band gap at 2.6 eV in core-shell BVO/ZnO. The interfacial band gap enhances the PEC performance with an increase in the efficiency of visible light-absorption and electron-hole separation. In addition, the distortion in the interface of core-shell BVO/ZnO with the high interfacial defects affects the O 2p -V 3d hybridization, resulting the high electron-hole separation at the interface to improve PEC performance. This study provides the evidence that the high PEC properties in nano-structure core-shell BVO/ZnO heterostructures are developed by the strongly CT, high electron-hole separation and large visible light-absorption at the interface due to the increase in defects in the core-shell interfaces. These insights from the local electronic and atomic structures in BVO layer coated ZnO nanodentrites may guide the fabrication of semiconductor heterojunctions with optimal compositions and interface that are highly desired to maximize the solar light utilization for PEC water splitting and their applications.

Keywords: Heterojunction photocatalysis, Charge transfer, Oxygen defects, X-ray spectroscopy, Core-Shell nanodendrites material