Defect sealing in Pd membranes via point plating

Defects in Pd and Pd–Ag membranes have been successfully sealed by directed electroless plating, which was achieved by feeding the metal source and the reducing agent from opposite directions to the defect zone. Optical microscopy showed that the surface texture of the metal layers was well preserved in the vicinity of cracks and pinholes, indicating that Pd deposition was effectively restricted to defect sites. The ideal H2/N2 selectivity could be improved by more than an order of magnitude during these point plating experiments while the very high H2 permeability of the membrane was completely retained, indicating that the overall metal layer thickness had not increased.