Preparation and study of ternary metal oxide photocathodes for solar energy conversion

Abstract

The future energy demand will require a change in the current energy supply. In this regard, the production of hydrogen by photoelectrochemical solar cells is a promising alternative because the fuel is obtained from water and, importantly, its combustion is free of carbon. Many metal oxides, including those having a complex stoichiometry (i.e. ternary oxides) behave as semiconductors and present good stability in aqueous environments, making them attractive candidates for water splitting devices. This thesis focuses on the preparation and study of ternary metal oxide materials as photoelectrodes for water splitting, with emphasis on photocathodes. These materials must meet the requirements for a practical device: low cost, non-toxicity, made of Earth abundant elements, environmentally friendly, etc. The thesis also aims at the study of strategies to improve their photoelectrochemical response. lt comprises the investigation of the kinetics of hydrogen generation reaction and the characteristics of the electrode solution interface by photoelectrochemical impedance spectroscopy. The main points can be summarized as: (i) the effect of an electrochemical oxidative pretreatment in CuFe2Ü4 photocathodes (ii) the investigation of water splitting mechanisms in CaFe2Ü4 photocathodes, (iii) the effect of metal doping in LaFeO3 photocathodes (iv) the study of the photoelectrochemistry of compact and nanoparticulate YFeO3 photocathodes and (v) the effect of a reductive electrochemical treatment in NiTiO3 photoanodes, and comparison with the effect of the treatment in anatase electrodes.