(596g) Intermetallic Hydrogen Separation Membranes: Synthesis and in-Situ Characterization

In contrast to disordered substitutional alloys, the crystal structures of intermetallic compounds are different from those of the components, and the component atoms occupy definite positions on the lattice. The atomically-ordered crystal structures of intermetallics results in some unique properties that have been exploited in several fields, including H₂ storage and catalysis. Although intermetallic membranes have received minimal attention, they are very promising as H₂ separation membranes. Our work suggests that intermetallic PdCu membranes perform better than disordered alloys. For example, intermetallic PdCu has higher H₂ permeability than all disordered PdCu alloy compositions, including pure Pd [1]; intermetallic PdCu resist corrosion from H₂S under conditions that result in severe corrosion of randomly disordered PdCu alloys [2]; and intermetallic PdCu is more resistant to CO poisoning than pure Pd membranes [1]. In this talk, I will discuss our method for preparing thin intermetallic membrane films using thermal evaporation of the metal constituents onto porous stainless steel substrates with an Al₂O₃ intermediate layer. This deposition technique allows us to prepare intermetallic membrane thin films with an extremely high degree of control over their composition, crystal structure, and film thickness. Furthermore, this technique allows us to deposit metals (e.g. Ga, Zn, Sn, In) that could not be deposited by more traditional deposition techniques, such as electroless deposition and sputtering. I will also discuss a unique operando spectroscopy tool that we have developed to interrogate the interactions of reactive gases with intermetallic membrane surfaces in-situ under realistic permeation conditions in order to understand why intermetallic membranes are more resistant to poisoning than disordered alloys. The development of new intermetallic membranes that resist poisoning from reactive gases could enable new energy technologies, including membrane reactors for modular chemical process intensification.

[1] C.P. O’Brien, I.C. Lee, The interaction of CO with PdCu hydrogen separation membranes: An operando infrared spectroscopy study, Catal. Today, in press.

[2] C.P. O'Brien, B.H. Howard, J.B. Miller, B.D. Morreale, A.J. Gellman, Inhibition of hydrogen transport through Pd and Pd₄₇Cu₅₃ membranes by H₂S at 350 degrees C, J. Membr. Sci., 349 (2010) 380-384.