Yuanyuan Shi

MATERIALS AND MOLECULES FOR POLLUTION FREE CLEAN ENERGY

The combustion of the fossil fuels has caused the global environment and energy problems, which influences human health and activities. With the motivation to make our contributions to solving these problems, we have performed a series of investigations to explore materials and molecules for pollution free clean energy, which is solar energy converted hydrogen in this thesis. We have statistically analyzed the airborne pollutant particles, PM2.5 particles, which indicates that the carbon-rich fluffy soot aggregates always show very high adhesiveness and aggregation. And more than 50% PM2.5 particles strongly interact with the substrate through a ultra-thin (< 10 nm) dark trace layer, which is very stable even under mechanical stress and it is consisted of alkali metals, hydrogen and CH groups. After the study about airborne pollutant particles, we have moved to the study of solar-driven water splitting devices for exploring the large-scale generation of hydrogen. In this thesis, we have mainly focused on the investigation of the materials and molecules for photoelectrochemical (PEC) and photovoltaic-electrolysis (PV-EC) water splitting devices. Our results show that in the PEC water splitting devices, copper and nickel metallic thin films can be deposited on the surface of silicon photoanodes, which can form CuO and NiOX respectively and then serve as very active catalysts for water oxidation reaction and a protecting layer for silicon surface from corrosion. And in PV-EC water splitting devices, the ruthenium molecular catalysts based anode has been used for the electrolyzer, which has been integrated with commercially available triple junction solar cells. This integrated PV-EC device achieves the highest solar-to-hydrogen efficiency of 21.2 % at neutral pH and just under solar illumination without any external bias. These results pave the way for the generation of large-scale solar converted hydrogen.

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