| In Part I, preparation of CdS and CdSe films on various electrode materials including nanoporous TiO2 and their photoresponses were demonstrated. Both electrochemical and chemical deposition methods successfully produced Cd-chalcogenide films and post-thermal treatment was done to develop respectable photoactivity. Chemical and photo-electrochemical etching were also performed to remove impurities and increase film stability. Transparency issues for a sandwich type of a solar cell based on semiconductor thin films on a TiO 2 porous nanostructure were examined by measuring transmittances of different wavelengths of laser light. Porous TiO2 films were made from both Degussa P25 TiO2 and Ti(IV) isopropoxide sol-gels. CdSe films on both TiO2 substrates showed comparable photospectra, but the sol-gel one is more transparent and shows better net response.; In Part II, electrodes of conductive nitrogen-incorporated tetrahedral amorphous carbon films (taC:N) deposited at ambient temperatures were shown to possess an extraordinary combination of the stability associated with boron-doped diamonds, yet with much enhanced electrocatalytic properties. In this study on the electrochemistry of deposited thin films of taC:N, we showed that this material demonstrates more active charge transfer properties on a variety of systems relative to the H-terminated, highly boron-doped diamond (B-diamond). Stability was shown by chlorine evolution from HCl solution for >104 times the coulombs necessary for 4e/C-atom oxidation to CO2 of a 40 nm thick taC:N film without noticeable change of the voltammetry.; Cu deposition and stripping on taC:N electrodes have revealed several distinctive features comparative to other electrodes. From stationary and rotating disk voltammograms, we observed a larger nucleation overpotential of Cu deposition on a taC:N electrode, and the extraordinary Cu stripping pattern, two peak or shoulder-peak, at the position about a higher (more positive) potential than normal bulk Cu stripping peak potential, in the region of the Cu(I)/Cu(II) process. RRDE evidence clearly showed a mixed process of oxidation of Cu(0) to Cu(I) or Cu(0) to Cu(II), and, especially, the presence of Cu(II) in the product stream. |
