Part I. Nanostructured semiconductor photoelectrochemical cells. Part II. Electrodes of tetrahedral amorphous carbon containing nitrogen

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.