Insights into the lanthanum doping effect on the hydriding of cerium-lanthanum alloy

Abstract

Hydriding reaction kinetics of cerium-lanthanum alloy was studied by the pressure-volume-temperature (PVT) method combined with in-situ microscope. The hydride nucleation and the H2 consumption rate approximately follow an exponential model at the initial time. Furthermore, the H2 consumption rate and the hydride nucleation were accelerated by the doped lanthanum (1–10%). The growth rate of the hydride sites approximately follows a linear law and it is not affected by the lanthanum content. An approximate parabola relation between the induction time and lanthanum content is evident. The hydriding reaction rate is accelerated by the doped lanthanum, which manifest as the accelerated H2 consumption rate, decreased induction time and accelerated nucleation. The results of XRD, Raman spectroscopy and Auger electron spectroscopy (AES) show that the oxide layer is constituted of CeO2 layer and nonstoichiometric transition layer, and the doped lanthanum can increase the concentration of the oxygen vacancies. The oxygen vacancies increase the active sites to accelerate the dissociation of absorbed hydrogen molecule and offers additional short-circuit diffusion paths to accelerate the transport of hydrogen atom in the oxide layer.