Date of Award
Doctor of Philosophy (PhD)
To relieve the global energy crisis and environmental pollution caused by the combustion of traditional fossil fuels, developing an environmental-friendly renewable energy to replace fossil fuel is urgent. Among the possible energy sources, solar energy has attracted numerous attentions because of the abundant storage. However, it is challenging to efficiently utilize and store solar energy. One attractive strategy to address this challenge is to convert solar energy to fuel through artificial photosynthesis (e.g. photocatalytic water splitting to generate H2). A technologically significant solar-driven water splitting system requires an efficient photocatalytic system that can not only effectively harvest light but also can perform the subsequent charge separation and catalytic reaction. The objective of my research projects is to develop such photocatalytic materials that can be used as light absorption and charge separation materials for light driven proton reduction to generate hydrogen. The materials that were of interest include semiconductor nanocrystals and porous crystalline materials. To establish their structure and property relationship, a suit of advanced spectroscopic methods including steady state absorption and emission spectroscopy, time resolved optical and X-ray absorption spectroscopy were used to examine their excited state, energy transfer, and charge separation dynamics during photoinduced reaction. One class of semiconductor photocatalytic materials that I have studied were CuInS2 quantum dots. The dependence of carrier dynamics of CuInS2 quantum dots on their sizes are presented in chapter 3. Their photocatalytic activity together with catalytic mechanism for visible light driven hydrogen generation are discussed in chapter 4. Zeolitic imidazolate frameworks (ZIFs), a subclass of metal organic frameworks (MOFs), are the second class of materials that I have investigated. The impact of the chemical compositions on ZIFs on their photophysical and photocatalytic property are discussed in chapter 5 and chapter 6. The energy transfer dynamics from the encapsulated chromophores to ZIFs is discussed in chapter 7 and chapter 8.