Studies on cuprous oxide and delafossite-based electrodes for use in solar energy conversion.

摘要

Materials which photoelectrolyze water to produce H 2 and O2 using visible light are of significant importance for solar energy conversion. As of yet, no single material has been found to effectively produce H2 and O2 from water while remaining cost effective and corrosion resistant. One solution is to assemble a p/n photoelectrochemical diode, where the p-type material produces H2 and the n-type material produces O2. Compared to the number of n-type semiconductors studied as photoanodes, the number of p-type materials studied as photocathodes to date have been limited, especially for oxide materials that can be easily processed. In this study, we report new electrochemical routes to prepare several p-type ternary oxides having a delafossite structure, ABO2, where A is a monovalent cation such as Cu+ and Ag+ while B is a trivalent cation such as Mn3+ and Fe3+. Their electrochemical and photochemical stabilities, band gap energies, flat band potentials, and photoelectrochemical properties will be discussed in detail.;Another important area of study in producing highly efficient photoelectrochemical cells is the optimum integration of semiconductor electrodes and catalysts (e.g. H2 or O2 evolution catalysts). The semiconductor-metal interactions can depend significantly on their interfacial structures. Therefore, understanding and manipulating the semiconductor/metal interfacial structure is critical in order to enhance desired properties of the composite materials. In particular, selective or atomic plane-dependent catalyst deposition is essential to construct highly structured composite architectures that can perform multiple functions in a spatially resolved manner. In this dissertation, I will introduce a new simple chemical route for selective metal deposition that is based on in-situ protection of certain atomic planes by additives during metal deposition. This method does not require any chemical or physical masking processes prior to metal deposition but allows for placing a catalyst only on desired locations in order to maximize both photo absorption and interfacial charge transfer properties of the semiconductor.