Enhanced Charge Transport via Electrochemically Formed Conducting Bridge in TiO2 Protection Layer of Photoelectrodes in Photoelectrochemical Water Splitting
Dong Su Kim a, Ji Hoon Choi a, Hak Hyeon Lee a, Shin Young Oh a, Hyung Koun Cho a
a School of Advanced Materials Science and Engineering, Sungkyunkwan University, Republic of Korea
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
#Adinos - Advances in inorganic thin film semiconductors for solar energy conversion: From photovoltaics to solar fuels
València, Spain, 2023 March 6th - 10th
Organizer: Sudhanshu Shukla
Poster, Dong Su Kim, 319
Publication date: 22nd December 2022

In typical photoelectrochemical (PEC) cells that use cuprous oxide (Cu2O), semiconductor photoabsorbers are passivated by protection layers such as TiO2. In these cells, there is an inevitable trade-off between high photocurrent and durable stability that is involved with the thickness of these layers in the typical energy band transport along the conduction band.[1] An outstanding conducting bridge transport mechanism for vigorous and robust PEC operation is innovatively proposed in this study as a strategically advanced charge transport mechanism. This mechanism is inspired by the concept of conducting bridge nano-filaments showing non-volatile metallic-like current flow characteristics in resistance-change memory devices. The purpose of this mechanism is to make PEC operations more efficient and reliable. The breakdown-like electrochemical forming behavior is effectively triggered by a rapid increase in current during a voltage sweep of over 2 VRHE, and the fundamental properties of filaments, such as diameter, density, and conductivity, have been controlled by varying artificially high compliance currents. Especially, it should be noticed that this process requires i) no top electrodes obstructing the light harvesting and the injection of photo-charges into electrolytes and ii) no individual forming process sweeping point-by-point bias, and provides iii) electrochemical forming sites with the homogeneous and dense distribution. Furthermore, by selecting to photoelectrodeposit co-catalysts preferentially, certain photocorrosive sites that cause photocurrent deterioration are completely passivated. The Cu2O/AZO/TiO2 photocathodes exhibit an unprecedented photocurrent density of about 11.9 mA/cm2, an open circuit potential of 0.73 V, and vigorous hydrogen and oxygen evolutions for over 100 hours despite the TiO2 passivation film having a thickness of more than 100 nm as a result of the electrochemical filament formation process and selective Pt-photoelectrodeposition on filaments.[2]

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A2C3011870). This research was also supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021M3F3A2A03017955).

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