Intermetallic GaPd₂ Thin Films for Selective Hydrogenation of Acetylene

The preparation of single-phase and catalytically active GaPd2 coatings was accomplished via DC magnetron sputtering using an intermetallic sputter target. Thin and uniform layers were deposited on borosilicate glass, Si(111) and planar as well as micro-structured stainless steel foils. The specimens were examined regarding their phase composition, film morphology and microstructure. Thin films of different layer thickness were catalytically characterized in the semi-hydrogenation of acetylene, which was conducted at 473 K and a feed gas composition of 0.5 vol.% C2H2, 5 vol.% H-2 as well as 50 vol.% C2H4 in helium. Pre-reduction of the catalyst was found to be essential to enhance the catalytic selectivity. Sputtered GaPd2 showed a high selectivity of 73 % for the hydrogenation to ethylene at conversion levels above 80 %. The surface-specific activity was strongly increased to 8.97 mol(acetylene)center dot(A(0)center dot h)(-1) compared to bulk- or nanoscale GaPd2 (1.93 and 0.30 mol(acetylene)center dot(A(0)center dot h)(-1), respectively) caused by the high specific surface area of the thin films.