Abstract

Natural photosynthesis has inspired the development of direct and indirect approaches for solar energy conversion into chemical bonds. The use of chemical bonds to store solar energy is a promising approach to address the intermittency of the sun by harnessing sunlight to drive chemical transformations. One strategy to drive these processes is to use a bespoke semiconductor surface implemented in a photoelectrode to absorb light and generate charge carriers that can drive redox reactions such as the direct oxidation of adsorbed species on the photoanode. Dye-sensitized photoelectrochemical cells (DS-PECs), devices inspired by photosynthesis, are being developed to advance the goal of using the sun as the sole source of energy for converting abundant resources to fuel and valuable chemicals. Furthermore, electrocatalysis shows great promise to achieve the goal of transitioning from the production of energy using fossil fuels to clean and renewable energy sources.
Herein, this thesis describes using compact and vertically aligned titanium dioxide nanotubes as semiconducting materials for applications in both photoelectrochemistry and electrocatalysis. Functionalizing with a molecular copper(I) bis(diimine)-based donor-chromophore-acceptor assembly yields a photoanode capable of carrying out oxidative processes. Surface characterization and photoelectrochemical studies point to the nanotubes being intrinsically sensitized with carbon impurities such as carbon nitrides for visible light absorption. The ability of unfunctionalized and dye-sensitized photoanodes to drive oxidative processes is further confirmed photoelectrochemically and in the presence of a water oxidation catalyst where a Faradaic efficiency of 84% is found for O2 production. Titanium dioxide nanotubes with distinct morphologies arising from different electrolyte compositions used in the synthesis process are decorated with photoelectrochemically deposited CoOx and used as an electrocatalyst for hydrazine oxidation and as an electrochemical transducer for hydrazine sensing. Although a substantial amount of work remains to be done to assess the anode-supported electrocatalyst against other existing systems, the device shows promise for sensing hydrazine.