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The cathodic dark current at n-type Nb-doped TiO2 and Ha-treated SrTiOs electrodes in Fe(CN)63-, Fe +3, or IrC162-aqueous solution was meastired as a function of applied voltage, concentration of oxidizing agent, and pH. Two distinct current regimes were observed, differing by their Tafel slopes and by their concentration dependence. The most marked feature of the results was the saturation of the current as a function of concentration in the high current-density region. The experimental data were interpreted on the basis of a model involving electron transfer through surface states. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-03-10 to IP VoI. I27, No. 2 ELECTROREDUCTION PROCESSES 325 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-03-10 to IP

F. Vanden Kerchove et al.: Electrochemical and Photoelectrochemical Properties etc sponding to a kinetic energy spread of 0 to 27.2kJ/mol. Practically no kinetic cooling will result from collisions with Nz and 02, since these molecules are extremely efficient quenchers of O('D). However, the presence of a minor constituent in excess of the stratospheric N,O mixing ratio of less than 0.3 ppm would sufiice to reduce the average kinetic energy of those O('D) atoms which react with NzO, provided that the quenching efficiency of the minor constituent is much less than unity. This condition is met by the noble gases [ 163, and by Argon in particular. -Anyway, to obtain the yield of NO molecules per N 2 0 reacting with O('D) in the stratosphere, b = kzb/k2 has to be known for kinetic energies of O('D) below 27.2 kJ/mol. The value b = 0.617 0.015 obtained in this work is independent of kinetic energy in the range of interest, and corresponds to a yield of 1.23 NO molecules for each NzO molecule consumed by O('D). This is 23% higher than the yield of 1.00 which is widely used in model calculations. The recent results of Schiff [15] as well as Pirkle et al. [I41 fall between these limits. Elektrochemie 1 Hulbleiter 1 Oberfliichenerscheinungen 1 Phoroelektrochemie / StromverdoppelungThe photoelectrochemical behaviour of several reagents at the Sr'TiO, anode has been investigated. Current-doubling was found with several reducing agents. By competitive reaction experiments, hole capture was detected with some other reagents. Quantitative data on relative hole reactivities were obtained for several reducing agents, including water. The position of the band edges at the semiconductor surface was deduced from capacitance measurements. The reactivity data are interpreted in terms of the position of electron energy levels at both sides of the surface, and the applicability of the direct electron transfer model to the reactions observed is discussed. Untersucht wurde das photoelektrochemische Verhalten verschiedener Reagenzien an der SrTi0,-Anode. Bei verschiedenen reduzierenden Zusatzen wurde Stromverdoppelung gefunden. Aus einer Untersuchung von Konkurrenzreaktionen wurde bei einigen anderen Reagenzien Defektelektronenfang festgestellt. Quantitative Ergebnisse in bezug auf relative Defektelektronenreaktivitaten wurden fur verschiedene Reagenzien, einschlieBlich Wasser, erzielt. Die energetische Lage der Bandkanten an der Halbleiteroberflache wurde aus Kapazitatsmessungen abgeleitet. Die Reaktivitatsergebnisse wurden aufgrund der energetischen Lage der Elektronenniveaus an beiden Seiten der Phasengrenze interpretiert, und die Anwendbarkeit des direkten Elektronenubergangsmodells auf die beobachteten Reaktionen wird besprochen. Absorptionsspektren, von Kristallen Elektrochemie I Halbleiter / Oberjlachenerscheinungen 1 PhotoelektrochemieA comparative study was made on the photocurrent of etched and mechanically polished n-GaAs single crystal electrodes. The photocurrent was investigated as a function of voltage, light intensity a...

Der kathodische Dunkelstrom an Nbdotierten NiOz‐ und durch partielle Reduktion in H2 halbleitend gemachten SrTiO3 ‐Elektroden in wäßrigen Fe(CN)6′‐, F e3 ‐ oder IrClä ′‐Lösungen wird als Funktion der angelegten Spannung, der Konzentration des oxidierenden Reagenzes sowie des pH gemessen.