| The photochemical behavior of n-WSe(,2) single crystal electrodes in acetonitrile solutions containing various redox couples is described. Photoanodes with discontinuities in the van der Waals surface show large dark currents due to recombination of electrons with photooxidized solution species. The observed photopotentials at n-WSe(,2) are consistent with Fermi level pinning; the energy position at which pinning occurs depends on the density of surface states and the concentration of solution species. The characteristics of a photovoltaic cell based on the generation of chlorine is described.;The dark electrochemical polymerization of o-phenylenediamine at n-MoSe(,2) and n-WSe(,2) single crystals is described. The photoresponse of electrodes subjected to polymerization is considerably improved as compared to untreated electrodes. The results are consistent with a decrease in recombination rate due to the blockage of surface states. Increases in the solar-to-electrical energy power efficiency of several photoelectrochemical cells range from 30 to 300 percent after surface pretreatment.;The electrogenerated chemiluminescence (ecl) based on the reaction of electrogenerated Ru(2,2'-bipyridine)(,3)('+) with the oxidizing species, peroxydisulfate, is described. The ecl mechanism involves several pathways and includes the quenching of excited-state Ru(bpy)(,3)('2+) by peroxydisulfate to produce several strong oxidants also capable of generating the excited state. An analogous chemiluminescence (cl) system based on reduction by magnesium is also described. The ecl and cl intensities are several times larger than previous systems based on Ru(bpy)(,3)('2+).;The mechanism of charge-transport through Nafion polymers coated on glassy-carbon electrodes and containing various electroactive cations is described. The apparent diffusion coefficient of charge through these electrode coatings is compared to the actual diffusion coefficient of mass transport of the electroactive species. The results are discussed in terms of the Dahms-Ruff model, where both physical diffusion and an electron-exchange component can contribute to the observed behavior. |
