Thermal stability study of Pd-composite membrane fabricated by surfactant induced electroless plating (SIEP)

ABSTRACT

Over the years, several different methods have been developed by modifying the conventional electroless plating (CEP) technique to fabricate dense thin Pd composite membranes with high H₂ permselectivity. In this study, Pd composite membranes on macroporous stainless steel substrate (MPSS) were fabricated using CEP and novel surfactant induced electroless plating (SIEP) methods. The structural characteristics of CEP and SIEP fabricated Pd membranes were investigated before and after the heat treatment using SEM, XRD, EDS, and AFM techniques. The H₂ permselectivity performance of the SIEP membranes was compared with that of CEP at different temperatures and trans-membrane pressures in the range of 523-823 K and 20-100 psi, respectively. The long-term thermal stability test of SIEP fabricated membranes was carried out on two different membranes, fabricated on MPSS substrates with and without oxide layer at 15 psi trans-membrane pressure and thermal cycling of 573-723-573 K. The microstructure analysis revealed that SIEP membranes have finer grains and diffused grain boundaries resulting in uniform, smooth, continuous, and pinhole free Pd-film. The SIEP membrane showed eight-fold higher H₂ flux (1.7172 mol/m²/s) and four-fold higher H₂ selectivity (~148) at 823 K and 100 psi trans-membrane pressure, compared to CEP membrane. Pd/MPSS membrane subjected to test for long-term performance and thermal cycling showed stable performance up to 1200 h while maintaining infinite H₂ selectivity. Interestingly, although the thickness of Pd/oxi-MPSS (13.49 µm) membrane was higher than that of Pd/MPSS (11.6 µm) membrane, the H₂ flux of Pd/oxi-MPSS membrane was two times higher than that of Pd/MPSS, attributed to the effective action of oxide layer as diffusion barrier.

KEYWORDS:

• Pd membrane
• H₂-permeability
• H₂-selectivity
• SIEP
• modified electroless plating
• membrane stability

Acknowledgements

The authors thank Dr. Jag Sankar, Dr. Sergey Yarmolenko, and Dr. Xu (Center for Advanced Materials and Smart Structures-CAMSS) at NCAT for the use of the XRD and SEM for material characterization.

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Additional information

Funding

This research was sponsored by the U.S. Department of Energy HBCU Program, under Award No. DE-FG08- NT000143. However, any opinions, findings, and conclusions or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the DOE. We gratefully acknowledge the financial support received from the National Science Foundation (NSF) (Grant No: HRD-124215) to reanalyze the previous data and to write this manuscript.