Graphite coating on alumina substrate for the fabrication of hydrogen selective membranes

摘要

Development of composite membranes is a suitable alternative to improve the hydrogen flux through palladium membranes. The porous substrate should not represent a barrier to gas permeation, but the roughness of its surface should be sufficiently smooth for the deposition of a thin and defect-free metal layer. In this study, the performances of the modification of the outer surface of an asymmetric alumina hollow fibre substrate by the deposition of a graphite layer were evaluated. The roughness of the substrate outer surface was reduced from 120 to 37 nm after graphite coating. After graphite coating, the hydrogen permeance through the composite membrane produced with 2 Pd plating cycles was of 1.02 x 10(-3) mol s(-1) m(-2) kPa(-1) at 450 degrees C and with infinite H-2/N-2 selectivity. Similar hydrogen permeance was obtained with the composite membrane without graphite coating, also at infinite H-2/N-2 selectivity, but 3 Pd plating cycles were necessary. Thus, graphite coating on asymmetric alumina hollow fibres is a suitable alternative to reduce the required palladium amount to produce hydrogen selective membranes. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.