Public defence in Engineering Physics, M.Sc. Xuelan Hou
Opponent is Professor Yun Hau NG, City University of Hong Kong, Hong Kong, P. R. China
Custos is Professor Peter Lund, Aalto University School of Science, Department of Applied Physics
Contact details of the doctoral student: [email protected]
The public defence will be organised in Otaniemi and via Zoom (Otakaari 4, lecture hall R008/216 and link to the Zoom event).
The dissertation is publicly displayed 10 days before the defence in the publication archive Aaltodoc of Aalto University
Hydrogen is a clean energy carrier that will play an important role in the energy transition toward net zero emissions. Unfortunately, hydrogen is presently produced from fossil fuels with major emissions. Therefore, the techniques to produce green H2 from renewable energy sources directly without CO2 emissions are highly relevant. In this thesis hydrogen production by photoconversion is investigated. Using sunlight and TiO2 nanotubes as photocatalysts, water can directly be split into hydrogen and oxygen. The focus of the thesis is on producing cheap and durable electrodes for photoconversion cells. Flexible and anti-corrosion titanium metal foils were used as substrates with self-fabricated TiO2 nanotubes as active sites, which were separately applied as anode and cathode electrodes. Electrochemical reduction methods were proposed to modify the pristine metal oxide to achieve higher performance and better stability, which is also time-saving and reduces the need for noble metals. The performance of the modified electrode as a cathode in a water splitting cell was even 17,000-fold higher than that of a pristine one, and 5-fold that of commercial titanium. When used as an anode, the modified electrode showed a 3-fold enhancement over the pure one (at 1.23 VRHE). In the photoconversion cell, the onset potential of the reduced anodic electrode had an anodic shift, corresponding to almost a doubling of the performance (at -1.0 VRHE). The reduction method for modifying p-type semiconductors is considered a potential method to prepare electrodes for water splitting cells.