Facile one-pot synthesis of PdM (M = Ag, Ni, Cu, Y) nanowires for use in mixed matrix membranes for efficient hydrogen separation†
Palladium (Pd) and palladium alloy nanowires (PdM; M = Ag, Ni, Cu, Y) of varying compositions were synthesized by facile and scalable one-pot polyol reduction of metallic salts using poly(vinylpyrrolidone) (PVP) as a capping agent. Alloy nanowires with a high surface area-to-volume ratio and an interconnected network (fractal-like) morphology may provide pathways for rapid hydrogen (H2) transport through a mixed-matrix membrane (MMM) containing them. The use of PdM nanowires provides two benefits. First, incorporation of a metal like Ag, Cu, Y, or Ni into Pd at an appropriate level can increase the H2 diffusivity while reducing the use of Pd. Second, alloying can reduce Pd embrittlement and susceptibility to poisoning. Polybenzimidazole (PBI) membranes loaded with PdM nanowires were prepared and tested at 150 °C and 100 psig for mixed gas H2/CO2 separation. MMMs containing 50 mass% pure Pd nanowires and 50 mass% Pd0.75Ag0.25 alloy nanowires showed H2 permeabilities of 53 and 38 barrer, respectively, which were dramatically increased from the permeability of 25 barrer for pure PBI.