Ruthenium hydrogen adsorption

Ruthenium was electrochemically deposited on platinum foil at a potential of 50 mV for 10 s. The cyclic voitammogram of this Pt—Ru electrode in 3 M H2SO4 is shown in Fig. 4—2. The voitammogram shows the hydrogen adsorption-desorption features from 50 mV to 200 mV and the oxidation and reduction current over 300 mV. The voltanunogram seemed stable when the upper limit potential was 800 mV. When the upper limit was higher than 800 mV, the voitammogram became slowly like pure... 

In a typical hydrogen adsorption experiment, ruthenium-copper aggregates are first contacted with flowing hydrogen in the adsorption cell at 400°C to ensure thorough reduction. The cell is then evacuated to a pressure of approximately 10-6 torr and cooled to room temperature for adsorption measurements. Isotherms for total hydrogen adsorption and for weakly adsorbed hydrogen are then determined in the manner described for nickel-copper catalysts in Chapter 2. 

In this paper, we postulate that the primary role of an alkali promoter is to reduce the mobility of the chemisorbed hydrogen on the ruthenium surface based on the data obtained from NMR spectroscopy. We will examine the active hydrogen adsorption states (a and P) in supported ruthenium catalysts and report the effects of the alkali promoters on the population and the mobility of the adsorbed states. 

In all three MEAs the rate of methanol oxidation was facilitated by the platinum-ruthenium unsupported catalyst, which in the presence of CO as a byproduct of the reaction, exhibit an electrochemical activity higher than pure Pt. However, compared to Pt supported and unsupported catalysts, the electrochemically active surface area of PtRu alloys cannot be determined by hydrogen adsorption using cyclic voltammetiy due to the overlap of hydrogen and oxygen adsorption potentials, and the tendency for hydrogen to absorb in the ruthenium lattice [xvi]. However, under the same operation conditions, cyclic voltammetry can be used for qualitative estimation of the similarity in the PtRu anode layer properties. 

The investigation of hydrogen adsorption of the activated carbon supported RuCla and carhonyl ruthenium (chlorine-free) indicates that the adsorption amount of the hydrogen of the sample containing chlorine is much larger than that of the chlorine-free sample (Table 6.24). 

Prom experiments of hydrogen adsorption at room temperature, Aika et al. found that when the molar ratio of Sm/Ru was 10, the adsorption amount of hydrogen will reduce to 1/3 of the origin, which indicates that there is a very strong interaction between ruthenium and lanthanide oxides. The chemisorption amount of hydrogen is not reduced obviously following the addition of CsOH on ruthenium surface. For example, when Sm/Ru =10.0, the H/Ru ratio will decrease to 0.18, while Cs/Ru = 10.1, the H/Ru ratio is 0.45. 

Other metals on silica supports have been investigated less extensively than platinum and nickel, and average particle diameters have only been estimated by gas adsorption methods, supported in a few cases by X-ray line broadening data. Thus, rhodium, iridium, osmium, and ruthenium (44, 45) and palladium (46) have all been prepared with average metal particle diameters <40 A or so, after hydrogen reduction at 400°-500°C. 

Adsorption is commonly used for catalyst removal/recovery. The process involves treating the polymer solution with suitable materials which adsorb the catalyst residue and are then removed by filtration. Panster et al. [105] proposed a method involving adsorbers made from organosiloxane copolycondensates to recover rhodium and ruthenium catalysts from solutions of HNBR. These authors claimed that the residual rhodium could be reduced to less than 5 ppm, based on the HNBR content which had a hydrogenation conversion of over... 

Electrooxidation of carbon monoxide to carbon dioxide at platinum has been extensively studied mainly not least because of the technological importance of its role in methanol oxidation in fuel cells [5] and in poisoning hydrogen fuel cells [6]. Enhancing anodic oxidation of CO is critical, and platinum surfaces modified with ruthenium or tin, which favor oxygen atom adsorption and transfer to bound CO, can achieve this [7, 8]. 

The co-existence of at least two modes of ethylene adsorption has been clearly demonstrated in studies of 14C-ethylene adsorption on nickel films [62] and various alumina- and silica-supported metals [53,63—65] at ambient temperature and above. When 14C-ethylene is adsorbed on to alumina-supported palladium, platinum, ruthenium, rhodium, nickel and iridium catalysts [63], it is observed that only a fraction of the initially adsorbed ethylene can be removed by molecular exchange with non-radioactive ethylene, by evacuation or during the subsequent hydrogenation of ethylene—hydrogen mixtures (Fig. 6). While the adsorptive capacity of the catalysts decreases in the order Ni > Rh > Ru > Ir > Pt > Pd, the percentage of the initially adsorbed ethylene retained by the surface which was the same for each of the processes, decreased in the order... 

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