Development of novel photocatalytic overall water splitting systems at elevated temperatures for efficient hydrogen evolution

Environmental and energy issues have become one of the most important issues that human beings are facing, and carbon neutrality is a communal target worldwide nowadays. With the strong international incentives to decarbonise our fuels and chemicals, the solar-light-driven photocatalytic overall water splitting (POWS) reaction provides a promising and renewable way to store and utilise the abundant solar energy in the form of hydrogen which is the cleanest chemical fuel for mankind. Numerous materials and catalytic systems have been developed for more effective solar energy conversion, however, the performance achieved so far is still unsatisfactory. In this context, this thesis has particularly focused on the design and development of novel POWS systems at elevated temperatures. Different semiconductor materials such as TiO2 and MoS2 were systematically studied in this thesis. In- depth catalytic activity studies illustrated the temperature effect on the POWS performance. Comprehensive surface characterisations combined with a series of spectroscopic, imaging and computational techniques were conducted to unravel the relationship between the activity and the structures of the catalysts. Subsequently, various strategies have been proposed for improving the POWS activity at elevated temperatures, including the use of local electric field and local magnetic field. Remarkable charge polarisation effects have been identified in each case. Finally, it is demonstrated that the POWS system studied in this thesis could split seawater into H2 and O2 with extraordinarily high solar-to-hydrogen conversion efficiency of 20.3 % at 270 oC, exhibiting high potential for future practical applications.