Experimental and Numerical Study of Pd/Ta and PdCu/Ta Composites for Thermocatalytic Hydrogen Permeation

Abstract

The development of stable and durable hydrogen (H<INF>2</INF>) separation technology is essential for the effective use of H<INF>2</INF> energy. Thus, the use of H<INF>2</INF> permeable membranes, made of palladium (Pd), has been extensively studied in the literature. However, Pd has considerable constraints in large-scale applications due to disadvantages such as very high cost and H<INF>2</INF> embrittlement. To address these shortcomings, copper (Cu) and Pd were deposited on Ta to fabricate a composite H<INF>2</INF> permeable membrane. To this end, first, Pd was deposited on a tantalum (Ta) support disk, yielding 7.4 x 10<SUP>-8</SUP> mol<INF>H<INF>2</INF></INF> m<SUP>-1</SUP> s<SUP>-1</SUP> Pa<SUP>-0.5</SUP> of permeability. Second, a Cu-Pd alloy on a Ta support was synthesized via stepwise electroless plating and plasma sputtering to improve the durability of the membrane. The use of Cu is cost-effective compared with Pd, and the appropriate composition of the PdCu alloy is advantageous for long-term H<INF>2</INF> permeation. Despite the lower H<INF>2</INF> permeation of the PdCu/Ta membrane (than the Pd/Ta membrane), about two-fold temporal stability is achieved using the PdCu/Ta composite. The degradation process of the Ta support-based H<INF>2</INF> permeable membrane is examined by SEM. Moreover, thermocatalytic H<INF>2</INF> dissociation mechanisms on Pd and PdCu were investigated and are discussed numerically via a density functional theory study.