In Situ Nanoultrasonic Imaging of Anodic Oxidation during Photoelectrochemical Water Splitting
Chih-Chiang Shen1,2*, Meng-Yu Weng1, Jinn-Kong Sheu3, Chi-Kuang Sun1,2,4,5
1Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan
2Molecular Imaging Center, National Taiwan University, Taipei, Taiwan
3Institute of Electro-Optical Science and Engineering and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan, Taiwan
4Institute of Physics and Research Center for Applied Science, Academia Sinica, Taipei, Taiwan
5Graduate Institute of Biomedical Electronics and Bioinformatics and Center for Optoelectronics Medicine, National Taiwan University, Taipei, Taiwan
* presenting author:Chih-Chiang Shen,
Photoelectrochemical (PEC) water splitting, one of the methods for hydrogen generation, takes the advantage of using solar energy to split water is regarded as a solution to the energy issue. The chemical reaction of energy transfer happening at solid/liquid interface faces the problem of stability and efficiency. To study and monitor the stability and efficiency problems of an electrode, a technique with capability to in situ image the structure of an electrode at solid/liquid interface is needed. In this study, the capability of nanoultrsonics to in situ monitor a chemical reaction at solid/liquid interface is investigated. The surface of n-GaN used as photoelectrode in PEC water splitting is taken as an imaged model for nanoultrasonics technique.We in situ monitor a growth of oxide film process at n-GaN/water interface in PEC water splitting for hydrogen generation. The in situ real time ultrasound image can show the thickness of etched n-GaN cap layer and the thickness of growth Ga2O3 thin film with atomic resolution.The nanoultrasonics gives a way to image a dynamic change of structure at solid/liquid interface with atomic spatial resolution under atmospheric conditions.

Keywords: Nanoultrasonics, Photoelectrochemical water splitting