Electroless Plating of Palladium Membranes on Porous Substrates for Hydrogen Separation and the Effects of Process Factors on Plating Rate and Efficiency: A Review
Abubakar Alkali
Abstract
The electroless plating of palladium and palladium alloy membranes is fast becoming an important and enabling technology. This is more so when juxtaposed with the rising demand for high purity hydrogen for applications particularly in proton exchange membrane fuel cells (PEMFC). The effect of process factors such as sensitization and activation during surface modification, concentration of the reducing agent, plating temperature, time, pH, additives, air aeration on plating efficiency, quality of the palladium film and deposit morphology is reviewed with the aim of identifying areas requiring further investigation. The paper also reviews how these process factors could be optimised for better plating efficiency and overall membrane quality. The concentration of the reducing agent has been identified as the limiting factor on plating efficiency albeit other process factors separately impact on the plating efficiency. Furthermore, bulk precipitation caused by concentration of the reducing agent has been identified as a major problem during electroless plating with hydrazine based plating baths. To ameliorate this problem, a multi step addition of the hydrazine reducer in separate portions has been recommended.