Comparison of Electroless and Electrodeposition of Pd-Ag Alloy on hydrogen separation performance

In the work presented here, palladium-silver membrane has been prepared by Electroless and Electro-deposition methods on porous stainless steel (PSS) substrate. The PSS substrate was washed with acetone and rinsed with distilled water, afterwards chemically cleaned using a 10% sodium chloride solution at 55°C and finally rinsed with distilled water. In Electroless deposition, the Pd-Ag alloy was fabricated by ethylene glycol as a new reducing agent and polyol process at 120°C for 10 minutes. In electrodeposition, the membrane was prepared using cyclic voltammetry and chronopotentiometry technique from alkaline solution containing tetraamminepalladium (II) chloride monohydrate, silver chloride and ammonium hydroxide at room temperature. The Electrodeposition carried out in the potential range of -1V to +1 V vs. The morphology of resulted alloy on PSS was analyzed by the scanning electron microscopy (SEM) and the phase structures of the coatings were examined by an X-ray diffractometer (XRD). The surface compositions were analyzed with an energy dispersive spectrometer (EDS) as well as hydrogen permeation analysis. The hydrogen separation tests confirmed the membrane coated by Electroless method is more highly selective towards hydrogen compared to other ones prepared by electro-deposition which could be attributed to the formation of dense and homogenous microstructure with finely divided powder and nano-sized pores as it could not be achieved in electro-deposition. Furthermore, the results showed that, 77:23 is the optimum ratio of Pd to Ag in both methods. The hydrogen separated gas of the optimized Pd/Ag membrane 409 showed the purity as much as 63.57% and 68.26% at 60°C and 120°C respectively for the electrodeposited membranes whereas it was equal to 99.9903% and 99.9936% at 60°C and 120°C respectively in the case of Electroless deposited membranes. SEM images of a typical Pd/Ag alloy coatings at PSS substrate in both methods is presented in Fig. 1. Also, the EDS analysis results are illustrated in Fig. 2.