Hydrogen Bronze Formation within Pd/MoO₃Composites

Abstract

In this study, Pd−Mo alloys have been internally oxidized to form Pd/MoO3 composites, and it is shown for the first time that H2 reacts with these composites to form H-bronzes, for example, H x MoO3, within the Pd matrix. The Pd matrix is the source of mobile H atoms, which react with the oxide precipitates to form H-bronzes. The kinetics of H-bronze formation are extremely fast. Solubilities of H2 in the Pd/MoO3 composites have been measured, and because H2 solution in the oxide is so much more exothermic than that in the Pd matrix, the former can be separated from the latter. The intercept of the solubility plot along the H content axis gives the stoichiometry of the H-bronze formed. Some irreproducibility was found in the p H 2 versus r relationships, which is also found in H-bronzes prepared by other techniques such as H spillover. The relative partial enthalpies of H2 solution, ΔH H, in the H-bronzes have been determined by reaction calorimetry as a function of the H content of the bronze. The ΔH H values decrease sharply in exothermicity with increasing x in H x MoO3.

Hydrogen and oxygen reaction on SiO2 and MoO3 supported Pd-Pt catalysts

“…The activity of Pd-Pt/MoO 3 after the heat treatment in N 2 at 150 0 C decreases and like in the first test, it also decreases during the repeated use of the catalyst. The heat evolved in the first and repeated experiments both are the same 364 kJ/ mol H 2 and they are distinctly higher than that evolved in employed is exothermic process similarly to what was previously observed [17,30,31]. The systematic studies reported by Noh et al [30] demonstrated that the kinetics of H-bronze formation is an extremely fast process.…”

“…The heat evolved in the first and repeated experiments both are the same 364 kJ/ mol H 2 and they are distinctly higher than that evolved in employed is exothermic process similarly to what was previously observed [17,30,31]. The systematic studies reported by Noh et al [30] demonstrated that the kinetics of H-bronze formation is an extremely fast process. The incorporation of hydrogen to the MoO 3 was observed to be much more exothermic than that in the Pd matrix (ΔH = -10.3 kJ/mol of ½ H 2 observed during the formation of a diluted PdH phase) [32].…”

HxMoO3@C nanobelts: Green synthesis and superior lithium storage properties

“…In previous work, the H x MoO 3 was obtained from MoO 3 by the reduction-intercalation mechanism, such as employing Zn/HCl aqueous solution, or spillover method of MoO 3 coated with Pt under hydrogen atmosphere [10,16,17]. For example, Qin et al reported the preparation of H x MoO 3 nanobelts using Mo powder, H 2 O 2 as reactants, ethanol as reducing agent [18].…”

Superior MgH2 Kinetics with MgO Addition: A Tribological Effect

“…The possible role of Nb 2 O 5 acting as a pathway for hydrogen diffusion within the magnesium matrix is similarly controversial [26][27][28]. Some metal oxides such as WO 3 , MoO 3 , V 2 O 5 , capable of forming a so-called hydrogen bronze phase have been shown to be good proton conductors [21,[29][30][31], however a noble catalyst is needed at the surface of the oxide to split hydrogen [29,30].…”