The need to tap renewable energy resources has grown enormously due to the recent adverse changes in global climate and depleting energy resources. Although solar energy conversion for electrical facilities has been a fore runner in the area of renewable energy resources, several important goals need to be met to fully utilize solar energy for the global energy demand. The use of a dye sensitized electrode in photoelectrochemical (PEC) water splitting is a new area of research with significant potential for the development of high performance solar fuel systems (1). Moreover, the Department of Energy has targeted the solar to hydrogen (STH) efficiency by PEC at 15%. However, the current performances of these systems are very poor. The quantum yields range between 2-3% of visible light. Of the various obstacles faced by this technology, one of the foremost is adherence of the dye to the semiconductor substrate, leading to the fast fading of the energy density. The chemical attachment of the dye to the high surface area TiO2 is an important and subtle issue. Information on the adhesion of the dye is not addressed significantly. Though sporadic information on high performing Ru-free sensitizers is available, the use of p-conjugated polymers as sensitizer in a photoanode for water splitting is not common. Hence, in the present study, a p-conjugated polymer having alternating arrangement of 2,7-diethynyl-9,9-dioctyl-9H-fluorene unit and (N,N’E,N,N’E)-N,N’-(acenaphthylene-1,2diylidene) bis (4-iodoaniline)(BIAN) unit was synthesized, characterized and its application in photoelectrochecmical water splitting was carried out. Synthesis of n-type π-conjugated polymer was carried out by Sonogashira coupling reaction between the 2,7-diethynyl-9,9-dioctyl-9H-fluorene and BIAN monomer in the presence of palladium catalyst under nitrogen at 70oC using triethylamine and toluene as solvent. The 1H-NMR of polymer 3 had peaks of BIAN and Fluorene. The gel permeation chromatography showed the number average molecular weight of the polymer was in the range of 6800-7000. The UV-Vis spectroscopy of the Ru-polymer complex exhibited a lmax due to Metal to Ligand Charge Transfer (MLCT) in the visible region at 470 nm. In addition, the HOMO and LUMO energy levels were calculated using Gaussian 09W. Further, the PEC water splitting studies exhibited an appreciable increase in the photocurrent indicating potential to pursue advanced water splitting studies.

BIAN based π-conjugated polymer as sensitizer for photoelectrochemical water splitting

249th National Meeting (2015)

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