Surface Engineering of BiVO4-based Photoelectrochemical Cells for Water Splitting

Abstract: Photoelectrochemical (PEC) water splitting is a promising technology for converting solar energy into green hydrogen. The development of highly efficient, robust and cost-effective photoanodes has been established to be of essential importance for PEC water oxidation. BiVO4 has been deemed as one of the most up-and-coming metal oxide-based photoanode materials for PEC water splitting. Development of new surface engineering techniques for BiVO4 is therefore the subject of this thesis. In Chapter 1, a general introduction that centers on the solar fuel production by BiVO4-based PEC cells is presented. It concerns the working principles of PEC systems, current status of BiVO4-based photoanodes, and modification strategies for enhancement of the PEC activity. In Chapter 2, the characterization methods used in this thesis and the preparation of BiVO4 photoelectrode are introduced. In Chapter 3, a postsynthetic borate treatment is developed to decorate the BiVO4 surface. The PEC performance of as-prepared B-BiVO4 photoanode is evaluated and the mechanism of the PEC enhancement is subsequently investigated. Moreover, the layered double hydroxide-based cocatalyst is integrated with the B-BiVO4 substrate. The synergistic effects of borate treatment and cocatalyst on improvement of the PEC activity are discussed. In Chapter 4, a conjugated microporous polymer-based heterogeneous catalyst is applied to the surface modification of BiVO4. The PEC performance of the BiVO4/eCMP-Co hybrid photoanode is discussed. Furthermore, the origin of the PEC enhancement is investigated by charge kinetics studies.In Chapter 5, a metal-organic complex, cobalt phytate, is introduced on BiVO4 by photo-assisted electrodeposition in the form of an ultra-thin nanolayer. The PEC performance of the BiVO4/CoPhy integrated photoanode and the role of CoPhy in interfacial charge transfer is investigated.