Hydrogen bronze formation within Pd/MoO3 composites

In this study, Pd−Mo alloys have been internally oxidized to form Pd/MoO3composites, and it is shown for the first time that H2 reacts with these composites to form H-bronzes, for example, HxMoO3, 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/MoO3composites 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 pH2 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, ΔHH, in the H-bronzes have been determined by reaction calorimetry as a function of the H content of the bronze. The ΔHH values de...