Preparation of palladium-copper-silver alloy membrane on stainless steel for hydrogen separation

Abstract

An improvement and developement of ternary Pd-Ag-Cu alloy membranes on 316L stainless steel substrates for hydrogen separation have been prepared by electroless and electroplating techniques. It was found that, the microstructure and adhesion of the films was good which the effects of hydrogen embrittlement cannot be observed when used in the hydrogen separation at working temperature. Pd-Ag-Cu alloy ratio was controlled by plating time and metal composition for plating. The surface morphology, composition and phase structures of the membrane were investigated by scanning electron microscope equipped with energy dispersive x-ray diffraction and X-ray diffractrometer, respectively. The phase structure after annealing indicated the alloy composition of Pd-Cu, Pd-Ag and Pd-Ag-Cu were formed with highly uniform distribution of Pd, Ag and Cu metal throughout of the membrane. The hydrogen permeation flux which was measured at 350-500℃ in pressure differences of 1-3 atm. As a result, hydrogen permeance increased with operating temperature and pressure. The hydrogen permeation flux obtained from Pd membranes with the Cr₂O₃ as intermetallic diffusion barriers was higher than that without. Not only Pd-Ag-Cu alloy membrane has a high hydrogen permeance but also has a good mechanical property, which can prevent the hydrogen embrittlement.