Hydrogen and deuterium mass transfer and separation during hydriding-dehydriding of palladium studied by the NERD method

Abstract

The neutron induced elastic recoil detection (NERD) technique with monochromatic 14 MeV neutrons was applied to a hydrogen and deuterium concentration depth profile study during the hydriding—dehydriding process in palladium placed as a membrane or a membrane electrode within a gas or an electrolytic cell, respectively. It was found that hydrogen diffusion may be accompanied by a distinct α-β interphase boundary movement to the membrane exit whereupon a sharp growth of permeation gas flux takes place. An anomalous behaviour of gas flux was also revealed at the point of opposite β-α phase transition of the Pd-D system induced by the membrane heating. Dehydriding of the Pd-membrane as well as both hydriding and dehydriding of a membrane made from a Pd-Ag alloy do not reveal any concentration gradients in the membrane bulk. A much higher H/D isotope separation factor was found in the case of Pd membrane loading with an isotope mixture, when using electrochemical hydriding compared with that observed from gas surroundings.