This is the author's version of a work that was published in the following source:, A.; Schücking, M.; Jochem, P.; Steffens, H.; Fichtner, W.; Wollersheim, O.; Stella, K. (2017). Empirical carbon dioxide emissions of electric vehicles in a French-German commuter fleet test

A new in situ electrochemical method of functionalizing an oxide-free Ni surface is demonstrated using octanethiol. Initial adsorption results in a multilayer molecular film, which blocks both the hydrogen evolution reaction (HER) and re-oxidation of the Ni by ambient oxygen. However, excess octanethiol can be removed by rinsing with ethanol, leaving behind a monolayer that continues to protect against re-oxidation but gives rise to an unexpected enhancement in the HER, with a greater enhancement for longer film formation times. The presence of an octanethiol monolayer on the surface was confirmed by spectroscopic observation of the CH(2), CH(3) and thiolate groups using infra red spectroscopy, while X-ray photo-electron spectroscopy demonstrated the effectiveness of the thiol layer as a barrier to surface oxidation. The electrochemically prepared octanethiol film impedes oxidation of the Ni in air more effectively than a film formed by immersion in a solution of octanethiol in ethanol.

Large area (A = 6 cm 2), thin tantalum films (5 nm < d < 100 nm) are accomplished by evaporation from tantalum rods using small pocket e-beam evaporators. Using a sample to source distance of ≈20 cm, homogeneous amorphous films with a small surface roughness (<1 nm) can be prepared on glass. Films are characterized by scanning electron microscope images, atomic force microscopy, electrochemical oxidation and resistivity measurements as a function of film thickness. The samples show high resistivities of 200-2000 µ cm. The temperature coefficient of the resistivity (TCR) is negative, as characteristic for highly disordered metals. A theoretical description of the thickness distribution (evaporation from plane and hemispherical sources on plane targets) is given in the appendix.

When substituting conventional with electric vehicles (EV) a high annual mileage is desirable from an environmental as well as an economic perspective. However, there are still significant technological limitations that need to be taken into consideration. This study presents and discusses five different charging strategies for two mobility applications executed during an early stage long-term field test from 2013 to 2015 in Germany, which main objective was to increase the utilization within the existing technological restrictions. During the field test seven EV drove more than 450,000 km. For four out of five presented charging strategies the inclusion of DC fast charging is indispensable. Based on the empirical evidence five key performance indicators (KPI) are developed. These indicators give recommendations to economically deploy EV in commercial fleets. The results demonstrate that the more predictable the underlying mobility demand and the more technical information is available the better the charging strategies can be defined. Furthermore, the results indicate that a prudent mix of conventional and DC fast charging allows a high annual mileage while at the same time limiting avoidable harmful effects on the battery.

Anodic oxidation of thin aluminum and tantalum films was performed in an electrochemical droplet cell. Thicknesses from 2 up to 8 nm were employed on 10 nm thick aluminum and tantalum films. Under ultrahigh vacuum conditions the conductivity of the remaining metal film is monitored as function of time. Equally prepared oxide films were accomplished in metal-insulator-metal capacitors, which were used to monitor the capacitance as a function of time. The combination of the two experimental setups shows clearly, that small losses in the capacitance of aluminum oxide capacitors are due to slight thickening of the oxide even under vacuum conditions. Up to one monolayer of the base aluminum electrode can be oxidized during 10 5 s. Modeling in terms of migration of either oxygen anion interstitials or metal cation migration points preferably to the latter one. Tantalum oxide films of the same thickness show a much larger stability indicating either a lower content of mobile ions or a higher activation barrier for ionization and migration.

Heterosystems of metal/insulator/gold type with titanium oxide and tantalum oxide as internal barriers are studied using internal photoemission (IPE), field induced current transport (current transients after voltage steps) and chemical reaction induced current transport (chemicurrent). IPE investigations over a broad energy range from 0.8 to 4.5 eV allow a determination of the interstitial layers band gap and the maximum height of the internal tunnel barrier. The built-in field of the heterosystem is derived by the evaluation of the slope in the photoyield versus photon energy plot. Current transients recorded after voltage steps allow the determination of the heterosystems time constants which generally have a value of some milli seconds. In titanium oxide systems additional time constants with values of several 100 s appear for bias voltages >0.5 V. These time constants are assigned to slow processes altering the height of the titanium oxide barriers. and electron sources in spin polarized tunneling. 5 In the present work we present a comparative investigation of charge transport induced by different methods through thin oxide films. Charges are driven through the oxide by: i) application of a device voltage ii) illumination of the samples with monochromatic light at variable photon energies, leading to spectra of internal photoemission, iii) non adiabatic chemical surface reactions. All three methods are combined since it is possible to derive the nature of excited carriers transport through heterosystems.6 For aluminum and tantalum oxide heterosystems it was found, that they form a high pass filter for excited electrons and holes (defect electrons). 4,6 Since the height of the internal barriers for electrons and holes can be modified by an applied bias voltage, it became possible to characterize the spectra of excited charge carriers with energies below the vacuum barrier. Bias voltages of up to 1 V could be applied to the system which had an internal barrier height of 3 eV.To increase the detection efficiency for excited electrons travelling from the surface of a metal towards the bulk, one can either decrease the thickness of the top metal film of a heterosystem or one can reduce the height of the internal barrier. But with a decrease of the internal barrier the method of applying a bias voltage for tuning this barrier might become problematic, since tunnel currents become larger with lower barrier heights. Additionally, the influence of midgap states, impurities and remanent changes of the internal barrier might become more relevant for lower barriers.8,9 These problems are adressed in the present work.A comparison of metal/insulator/metal heterojunctions is presented with potentiostatically formed titanium and tantalum oxide as interjacent insulating layer. Titanium and tantalum oxide were chosen since both have bandgaps smaller than 4.5 eV.10 For amorphous tantalum oxide values of 4.2 eV are typical 11,12 whereas crystalline samples show values of 3.9-4.5 eV.12,13 Bulk titanium oxide values are for rut...

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