Design and Fabrication of Nanomaterials for Efficient Solar to Chemical Energy Conversion

Solar energy is a large, exploitable, renewable resource where it can supply the earth with enough energy in one hour, equivalent to the mankind’s total energy consumption in a year. Nanomaterials, for semiconductor material, used as a photocatalyst to convert sunlight into chemical fuel (hydrogen) via photoelectrochemical water splitting process, has been considered as the Holy Grail to a carbon free hydrogen economy. Conversion of sunlight into hydrogen is a promising, clean and sustainable way of generating hydrogen. In this research project we have designed, synthesised, characterised and tested new materials for which can generate hydrogen from water using solar energy. Due to the lack of suitable p-type semiconductor materials, this work has focused on synthesising and developing new, stable, visible light active photocathodes for solar hydrogen generation. In pursuit of this stable photocathode, we have synthesised stable visible light active LaFeO₃ which has shown some promise as a future candidate p-type photocathode. This was produced by cheap, novel and scalable spray pyrolysis technique which has resulted in current densities of 0.16 mA cm⁻² at 0.26 V vs RHE and shown stability over 21 hours. Subsequently, this led to hydrogen generation of 0.18 μmol cm⁻². Furthermore, LaFeO₃-Ag and LaFeO₃-Ni were fabricated by spin coating silver and nickel nanoparticles on to the spray pyrolysed LaFeO₃, to enhance photocurrent density for enhance hydrogen generation via solar water splitting. This led to over double the amount of hydrogen being produced. Similarly, TaFeO₄ was fabricated by sol-gel method which yielded 0.091 μmol g⁻¹ of hydrogen. Future work is required on TaFeO₄ to fabricate electrode form of the material so its band structure many be determined. This may be done by microwave assisted annealing.