Exploring Titanium Oxide Hydrate/Polyalcohol Inorganic/Organic Hybrid Fuels for Solar Energy Harvesting and Storage

Photo-rechargeable batteries are promising technologies that combine renewable energy harvesting and storage capabilities into one device, offering a unique solution to one major drawback of solar power, i.e., the intermittent availability of the sun. Current photo-rechargeable batteries and photo-fuel cells, to date, are, however, limited in their ability to store photochemical energy for long periods of time. Here, we demonstrate novel inorganic/organic fuels based on liquid titanium oxide hydrates mixed with various organic polyalcohols that may overcome these issues. Prior studies by our group have shown that titanium oxide complexes can be reduced from a Ti oxidation state of +IV to +III upon illumination with ultraviolet light. They can subsequently be oxidized in a galvanic cell to produce an electric current. We illustrate that the polyalcohol is not the species that directly oxidizes alongside titanium photoreduction upon irradiation with UV light. However, the nature of the polyalcohol is important as its chemistry influences the stability of the titanium oxide species vs. promoting hydrolysis towards TiO₂; it also affects the photochromic response of the hybrid solutions. The knowledge gained here will thus lay a knowledge platform towards a new class of photo-rechargeable fuel cells and batteries for renewable energy generation and storage.