Abstract.We studied structure and reactivity of ZnO(0001) ultrathin films grown on Ag (111) and Cu(111) single crystal surfaces. Structural characterization was carried out by scanning tunneling microscopy, Auger electron spectroscopy, low-energy electron diffraction, and temperature programmed desorption. The CO oxidation behavior of the films was studied at low temperature (450 K) at near atmospheric pressures using gas chromatography. For ZnO/Cu(111), it is shown that under reaction conditions ZnO readily migrates into the Cu crystal bulk, and the reactivity is governed by a CuO x oxide film formed in the reaction ambient. In contrast, the planar structure of ZnO films on Ag(111) is maintained, similarly to the previously studied ZnO films on Pt(111). At sub-monolayer coverages, the "inverse" model catalysts are represented by two-monolayer-thick ZnO(0001) islands on Pt(111) and Ag(111) supports. While the CO oxidation rate is considerably increased on ZnO/Pt(111), which is attributed to active sites at the metal/oxide boundary, sub-monolayer ZnO films on Ag(111) did not show such an effect, and the reactivity was inhibited with increasing film coverage. The results are explained by much stronger adsorption of CO on Pt(111) as compared with Ag(111) in proximity to O species at the oxide/metal boundary. In addition, the water-gas shift and reverse water-gas shift reactions were examined on ZnO/Ag(111), which revealed no promotional effect of ZnO on the reactivity of Ag under the conditions studied. The latter finding suggests that wetting phenomena of ZnO on metals does not play a crucial role in the catalytic performance of ZnObased real catalysts in those reactions.

Abstract. As a unique geological and geographical unit, the Tibetan Plateau dramatically impacts the world's environment and especially controls climatic and environmental changes in China, Asia and even in the Northern Hemisphere. Tibetan Plateau, therefore, provides a field laboratory for studying global change. With support from various agencies in the People's Republic of China, a Tibetan Observation and Research Platform (TORP) is now implementing. Firstly the background of the establishment of the TORP, the establishing and monitoring plan of long-term scale (5-10 years) of the TORP has been introduced. Then the preliminary observational analysis results, such as the characteristics of land surface heat fluxes and CO 2 flux partitioning (diurnal variation and inter-monthly variation etc.), the characteristics of atmospheric and soil variables, the structure of the Atmospheric Boundary Layer (ABL) and the turbulent characteristics have also been shown in this paper.

This work investigated the influencing factors on the stability of direct methanol fuel cells via testing a single-cell, which was conducted at 60°C under 100 mA cm -2 for 3,009 h. To completely uncover and interpret the performance degradation mechanism, electrochemical method (such as polarization curve, electrochemical impedance spectra, anode polarization voltammetry, methanol crossover and cyclic voltammetry tests), electron microscopy technique (SEM, TEM and EDX) and XRD spectroscopy were coherently performed in this work. The degradation rate in the whole test process is relatively steady, in which the cell voltage decreases 29% and the maximum power density decreases 35%. However, there is obviously an irreversible degradation when the cell runs at about 1,600 h. According to our analysis, the irreversible degradation of the cell is mainly caused by the increase of resistance and decrease of catalytic activity. Further, the increase of the resistance might be due to the increase of the interface resistance between cathode and Nafion membrane according to SEM results. In addition, the decrease of catalytic activity is mostly caused by Ru loss from anode side to cathode side and the agglomeration of catalyst particles in both electrodes.