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The discovery that supported gold clusters act as highly efficient catalysts for low-temperature oxidation reactions has led to a great deal of work aimed at understanding the origins of the catalytic activity. Several studies have shown that the presence of trace moisture is required for the catalysts to function. Using near-atmospheric pressure flow reactor techniques, we have studied humidity and temperature effects on the reactivity of gas-phase gold cluster anions with O2. Near room temperature, the humid source produces abundant gold-hydroxy cluster anions, Au(N)OH(-), and these have a reversed O2 adsorption activity: Nonreactive bare gold clusters become active when in the form Au(N)OH(-), while active bare clusters are inactive when -OH is bound. The binding energies for the stable structures obtained from density functional calculations confirm fully these findings. Moreover, the theory provides evidence that electron-transfer induced by the binding of a OH group enhances the reactivity toward molecular oxygen for odd anionic gold clusters and suppresses the reactivity for the even ones. The temperature dependence of O2 addition to Au(3)OH(-) and Au(4)(-) indicates deviations from equilibrium control at temperatures below room temperature. The effects of humidity on gold cluster adsorption activity support the conclusion drawn for the mechanism of O2 adsorption on "dry" gold cluster anions and provides insight into the possible role of water in the enhanced activity of supported gold cluster catalysts.

The reactions of Mo2Oy- suboxide clusters with both methane and ethane have been studied with a combination of mass spectrometry, anion photoelectron spectroscopy, and density functional theory calculations. Reactions were carried out under "gentle" and "violent" conditions. For methane, a number of products appeared under the gentler source conditions that were more logically attributed to dissociation of Mo2Oy- clusters upon reacting with methane to form MoCH2-, Mo(O)CH2-, and HMo(O2)CH3-. With ethane, products observed under the same gentle conditions were Mo(O)C2H2-, Mo(O)C2H4-, Mo(O2)C2H4-, and Mo(O2)(C2H5)2-. As expected, more products were observed when the reactions were carried out under violent conditions. The photoelectron spectra obtained for these species were compared to calculated adiabatic and vertical electron affinities and vibrational frequencies, leading to definitive structural assignments for several of the products.

Revision 0 vi 4. Liquid air interface tests at the new SCC limits LAI tests of carbon steel coupons exposed to simulants with different ratios of nitrite and nitrate were performed. Coupons exposed to simulants with a ratio of nitrite to nitrate of 1.66 showed negligible corrosion rates or pitting susceptibility. This can be expected since this inhibitor ratio meets the SRS requirement for pitting control. None of the coupons showed any signs of LAI. Minor areas of general surface attack were seen in the vapor space area. However, no pits or general corrosion areas were observed in the weld area of the coupons. There was also no correlation between heat treatment and the degree of corrosion observed. 5. Pitting corrosion studies using the standardized CPP protocol for the Argentinian work and additional dilute test solutions The results of the 18 repeated Argentina tests compared relatively well to original CPP test results. A second series of tests in simulants with nitrate concentrations ranging between 0.5-2 M resulted in 11 of the 12 cases indicating pitting. These results indicate that a pH of 12 is not always sufficient to prevent pitting initiation particularly if higher than normal quantities of chloride and sulfate are present. The results from these tests, along with other previous testing, will be utilized during FY16 for the development of new corrosion chemistry limits for pitting prevention. 6. Pitting corrosion studies using the standardized CPP protocol of new vs. legacy stock of A-537 steel for vitrification return stream All five heats of A-537 carbon steel underwent aggressive pitting corrosion in the two test simulants during the CPP test. To determine if there is an appreciable effect of the different heats of material, CPP testing in a simulant that is not aggressive and in one that produces mixed results may reveal differences (i.e., similar to the test protocol development).