Sustainable semiconductor materials and nanostructures for efficient and stable solar water splitting

Abstract

Solar water splitting using photoelectrochemical (PEC) cells has emerged as one of the most promising routes to produce hydrogen as a clean and renewable fuel source. The functional semiconductor materials and efficient nanostructures are the key to realizing the green hydrogen economy. My thesis research is directed at designing and constructing sustainable semiconductor materials and nanostructures for efficient and stable solar water splitting. Firstly, I developed new functional photoelectrodes and heterogeneous composites to boost the solar water splitting, including (1) the design and fabrication of the p-type ZnPbO₃ and n-type Zn₂PbO₄ as the new photoelectrodes for water reduction and oxidation, respectively. Additionally, it was the first time that unassisted solar water splitting was realized by combining the CoPi/Zn₂PbO₄ photoanode and the MoS₂/ZnPbO₃ photocathode. (2) the configuration of BiVO₄/BiFeO₃ composite with regulable polarization electric field, which achieved with synergistic ferroelectric and piezoelectric effects, accelerating the interfacial charge separation and transfer in heterojunction structure for PEC applications. Secondly, I applied various strategies to fabricate the nanostructured photoelectrodes to high performance and stability hybrid PEC systems, including (1) the novel strategy to extend the cocatalyst loading from 1D to 3D from the photoabsorbing semiconductor (PAS) in a cross-linked conducting polymer network. This scheme has been proved to greatly increase the redox reaction sites without decreasing the light absorption and effectively prohibit charge recombination. (2) in-situ growth strategy to form the intertwined nanointerfaces with uniform, continuous, fully engaged connection of the adjacent constituents. Meanwhile, the charge transfer direction has been further enforced through band structure tuning to make the photogenerated holes efficiently transfer through the nanointerfaces. In my thesis, various efficient and stable photoelectrodes have been developed with unique material properties and nanostructures for the excellent performance of solar water splitting. The chemicals, possible reaction mechanisms and factors that may affect the final PEC performance have been systematically investigated. Overall, these works shed light on designing and fabricating the sustainable semiconductor materials and nanostructures for the next-generation photoelectrodes and devices.

Date of Award	2020
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology