Facile one-pot synthesis of PdM (M = Ag, Ni, Cu, Y) nanowires for use in mixed matrix membranes for efficient hydrogen separation

Abstract

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% Pd_0.75Ag_0.25 alloy nanowires showed H₂ permeabilities of 53 and 38 barrer, respectively, which were dramatically increased from the permeability of 25 barrer for pure PBI.