XPS surface and bulk studies of heat treated palladium in the presence of hydrogen at 150°C

Abstract

Palladium metal powders used for hydrogen isotope pumping were studied for their bulk and surface chemistry changes during cleaning with hydrogen gas at 150 O C . Cleaning is necessary to promote rapid hydriding and dehydriding and to prevent contaminant ingrowth in the process gas during use. These studies show that heating the powders in vacuum at moderate temperatures (15OOC) in a reducing environment removes surface oxide, leaves a predominately palladium metal surface which presents no significant barrier to hydrogen absorption or desorption, and shows no loss in surface area and pourability. A surface model of PdO is given and XPS results show that the water-forming reaction is the mode of PdO reduction. Thermodynamic data are discussed which support the above results.

Surface functionalized silica as a toolkit for studying aqueous phase palladium adsorption and mineralization on thiol moiety in the absence of external reducing agents

“…The results shown in Fig. 3c suggest that the thiol-terminated silica was covered with palladium metal and PdO [31].…”

“…The Pd 3d 5/2 spectrum in Fig. 2c clearly shows the major Pd-S signal of 337.8 eV [30] with trace PdO (336.5 eV) [31]. The estimated atomic ratio of Pd:S of 1:1, calculated by the CasaXPS program, suggests the preferential Pd precursor binding on thiol, and the interfacial thiol density on silica as 9.4 Â 10 À5 mol/g.…”

New route to synthesis of PVP‐stabilized palladium(0) nanoclusters and their enhanced catalytic activity in Heck and Suzuki cross‐coupling reactions

“…Additionally, two other weak bands are observed at 339.8 and 344.8 eV, which most probably belong to a higher oxidation state of palladium, PdO x . [28] Since the nanoclusters are prepared from the reduction of potassium tetrachloropalladate(II) by sodium borohydride in the presence of PVP as stabilizer, palladium(0) might be oxidized on the surface of nanoclusters during the XPS sample preparation due to the air exposure. Figure 3 shows powder XRD diffraction patterns obtained for the PVP-stabilized palladium(0) nanoclusters.…”

Effects of hydrogen/deuterium absorption on the magnetic properties of Co/Pd multilayers

“…This interface was due to a purely magnetic contrast. In sample B, a slightly different model was used because data exhibited a half-order Bragg 28 In the / profile of sample A (Figure 10), the position of the PdO peak disappears completely, while for sample B there was still a peak, indicating that the PdO was not completely reduced. The magnetic SLD profile, , for samples A and B are shown in and Figure 12 and Figure 13, respectively.…”