Comparison of Electroless and Electrodeposition of Pd-Ag Alloy on hydrogenseparation performance

In the work presented here, palladium-silver membrane has been prepared by Electroless andElectro-deposition methods on porous stainless steel (PSS) substrate. The PSS substrate waswashed 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 at120°C for 10 minutes. In electrodeposition, the membrane was prepared using cyclicvoltammetry and chronopotentiometry technique from alkaline solution containingtetraamminepalladium (II) chloride monohydrate, silver chloride and ammonium hydroxide atroom 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 membranecoated by Electroless method is more highly selective towards hydrogen compared to other onesprepared by electro-deposition which could be attributed to the formation of dense andhomogenous microstructure with finely divided powder and nano-sized pores as it could not beachieved in electro-deposition. Furthermore, the results showed that, 77:23 is the optimum ratioof Pd to Ag in both methods. The hydrogen separated gas of the optimized Pd/Ag membrane showed the purity as much as 63.57% and 68.26% at 60°C and 120°C respectively for theelectrodeposited membranes whereas it was equal to 99.9903% and 99.9936% at 60°C and 120°Crespectively in the case of Electroless deposited membranes. SEM images of a typical Pd/Agalloy coatings at PSS substrate in both methods is presented in Fig. 1. Also, the EDS analysisresults are illustrated in Fig. 2.

Keywords:

Pd-Ag membrane , Electroless , Polyol process , Electro-deposition , hydrogenseparation