New electrode materials for the oxygen evolution/reduction reactions; solar cells based on novel solvent-free gel elctrolytes

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Metal-air batteries are energy storage systems attractive for portable electronic devices and electric vehicles due to their high specific energy and to the low cost and low toxicity of the electrode materials. Solar cells are devices that convert directly renewable solar energy into electricity. In order to improve the power density and lifetime of metal-air batteries, the long term objective of this proposal (Phase I) is to develop highly active and stable bifunctional oxygen electrode materials. In these devices, oxygen reduction (OR) is occurring during the discharge and oxygen evolution (OE) during the recharge, at the same electrode material. Novel MyCu1-yCo2O4 electrocatalysts (M = Mn or Li) will be dispersed on an Nb-doped TiO2 conductive support and fixed on a glassy carbon disk. The factors responsible for the electrode activity and stability will be assessed by studying the effects of the catalyst/support properties and of the electrode preparation parameters on the electrode properties and performance for the OR and OE reactions. O2- and air-feeded gas diffusion electrodes with an active layer containing the most promising catalyst/support powders will be investigated. The long-term objective of Phase II of this proposal is to develop a compact, highly efficient, stable and low-cost solar cell based on an original concept: a solvent-free gel electrolyte in junction with highly porous n-type CuInS2 or Cu(In,Al)S2 semiconductor; the catalyst CoS completes the device. Despite the advantages of using a gel electrolyte (e.g., mechanical stability), evaporation of the organic solvent will dry the gel and decrease the cell performance that should, on the contrary, be enhanced. Gel electrolytes, composed of new redox couples dissolved in an ambient temperature ionic liquid (very low vapor pressure) and incorporated in a polymer matrix, will therefore be developed. Also, the preparation of CuInS2 will be optimized and less expensive Cu(In,Al)S2 will be investigated. In order to get a better understanding of the factors responsible for the device performance, a series of redox couples, solvent-free electrolytes, nanosized CuInS2 and Cu(In,Al)S2 particles and films, and solar cells incorporating the optimal components will be characterized.