Study of pd-ag membranes with an intermediate oxide layer fabricated by surfactant induced electroless plating (siep).

摘要

Uses of fossil fuels in transportation and power generation release greenhouse gases. Hydrogen has the potential to be an alternative clean energy carrier. Hydrogen fueled proton exchange membrane fuel cell (PEMFC) can be used in transportation and stationary power generation to reduce greenhouse gas emissions. However, high purity hydrogen is required for PEMFC. In the current work, dense Pd-Ag composite membranes with an oxide layer on microporous stainless steel substrate (MPSS) were fabricated by surfactant induced electroless plating (SIEP) process for hydrogen separation. Prior to palladium/silver metal deposition, the MPSS disc was oxidized in stagnant air at 500 ºC for 18 h. A cationic surfactant, dodecyl trimethyl ammonium bromide (DTAB) was used in Pd- and Ag-bath for the sequential deposition of metals on MPSS substrates to remove the gas bubbles (N2 and NH3) produced during electroless plating. In this work, 4 CMC and 0.3 CMC (1 CMC = 15.6 mM) of DTAB were used in Pd- and Ag-bath respectively. Addition of a high amount of DTAB leads non-uniform Ag deposition and takes longer time to fabricate defect free Pd-Ag membrane. However, the average particle sizes were found to be 1.4 mum to 2.5 mum, which were relatively larger than the Pd-Ag film particle size using 4 CMC of DTAB in both Pd- and Ag-bath. Morphological features of the fabricated Pd-Ag membranes at pre- and post-annealing conditions were studied by using SEM, XRD, and EDS. The Pd-Ag membrane with an oxide layer showed higher permeability and selectivity in comparison to the membrane without oxide layer. However, at elevated temperature (550 ºC) the membrane showed a sharp decline in selectivity. The hydrogen flux and selectivity (H2/N2) of SIEP fabricated Pd-Ag membrane with an oxide layer were found to be 25.83 m3/m2-h and 500 respectively at 40 psi and 450 ºC.