Electrochemical investigation of electron-transfer cascades for the development of solar energy conversion based on artificial photosynthesis

Natural Photosynthesis process is the source of life; it converts the sunlight into chemical energy. This process takes place in the chloroplast of the green plants in a sophisticated and complex pathway. It involves electron transfer cascades from the photoexcited reaction centre to sustainable energy storage. As a route to develop new chemical systems for artificial photosynthesis in an efficient and fast electron transfer cascade, it is essential to propose three-dimensional molecular ensembles of both electrochemically and photochemically active systems. This thesis studies the behaviour of using L-cysteine and potassium iodide as electroactive species in a reduction reaction of chlorpromazine hydrochloride on glassy carbon electrodes and rotating glassy carbon disk electrodes with the aid of cyclic voltammetry and linear sweep voltammetry. The electrochemical characteristics of chlorpromazine hydrochloride (CPZ.HCl) in various concentrations, which induce catalytic oxidation reactions of different concentrations of the electroactive materials, are investigated. The experimental results show that the increase in oxidation peaks current of chlorpromazine hydrochloride depends on the concentrations of L-cysteine and potassium iodide. The current response was enhanced through fast transport via a rotating glassy carbon disk electrode. The peak potentials of chlorpromazine hydrochloride in the solution containing L-cysteine shift to more negative values for all concentrations and speeds; similarly for potassium iodide. The electrochemical reaction of chlorpromazine hydrochloride with the electroactive materials determined EC' reactions. The diffusion coefficient for chlorpromazine hydrochloride was found to be 1.28×10-6 m2 s-1. This thesis studies the adsorption and electrochemical investigation of one of the derivatives of chlorophyll-chlorophyllin, at gold and glassy carbon electrodes. Parameters such as the adsorption time, the electrolyte nature and concentration and chlorophyllin concentration were investigated. The use of chlorophyllin as a redox mediator was examined, with a gold electrode being employed. The importance of gold electrode surface preparation in determining the mechanism of redox was described, and the environment of adsorption process of the different concentrations of chlorophyllin on the surface of the gold electrode had been elucidated in this study. The electrochemical method shows that the cyclic voltammetry responses of studied adsorption chlorophyllin pigment on the gold electrode were more efficient than glassy carbon electrode, with processes being more favourable in aqueous solution. Third, the oxidation reaction of various concentrations of chlorophyllin is investigated in the bulk solution in the presence of Triton X 100 and potassium iodide. The extraction and identification of chlorophyll in fresh spinach were examined by using thin layer chromatography and UV-visible spectrophotometry techniques. The cyclic voltammetry for this pigment was elucidated in the presence of Triton X 100 and vitamin K1 at the gold electrode, the mechanism of this reaction was suggested to be EC'. Lastly, this study has emphasised chlorophyll a and Total chlorophyll (Tchl), based on the effect of electrode materials and diameter, pH, solvent and electrolyte. The inducing of electron transfer of Tchl pigment was examined in presence and absence of vitamin K1 through light and dark atmosphere. The system of chlorpromazine-lyotropic liquid crystal (CPZ-LLC) was highlighted in this thesis. The effect of parameters such as electrode materials, electrode diameters and CPZ.HCl concentrations in this system have been documented. The self-assembled phase was recorded using polarising optical microscopy and X-ray scattering. The CPZ-LLC system was fabrication into photogalvanic cells. The power conversion efficiency (PCE) of this cell is (0.58%), which is useful and novel.