Apparent activation energy for hydrogen permeation and its relation to the composition of homogeneous PdAu alloy thin-film membranes

Journal Article · Fri Sep 22 00:00:00 EDT 2017 · Separation and Purification Technology

DOI:https://doi.org/10.1016/j.seppur.2017.09.047· OSTI ID:1538814

Patki, Neil S. ^[1]; Lundin, Sean-Thomas B. ^[1]; Way, J. Douglas ^[1]

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1. Colorado School of Mines, Golden, CO (United States)

PdAu alloy composite membranes are often fabricated by sequential electroless plating of Pd and Au, but this forms a layered structure that must be annealed to form a homogenous alloy. Using ex situ analysis techniques such as X-ray diffraction (XRD) or energy dispersive X-ray spectroscopy (EDS) to judge the extent of homogenization can be time-consuming as the composite membranes must be cooled to ambient temperatures prior to analysis. However, an in situ alternative is to use the apparent activation energy for H₂ permeation (E_act). Here in this work, 27 – 41 wt% Au films were fabricated to expand upon a range of 0 – 21 wt% that has been previously reported. Homogenization (confirmed by XRD and EDS) was achieved by heat treatment in 3 MPa H₂ at 550 °C for up to 120 h. The apparent E_act was found to initially decrease with increasing Au composition from 12.2 kJ mol^-1 (pure Pd) to 7.5 kJ mol^-1 (21 wt% Au) after which it slowly increased to 9.0 kJ mol^-1 (41 wt% Au). The two distinct regimes can be explained using the relation E_act = ΔH_H + E_D, wherein E_act is the sum of the partial enthalpy of solution of H into the PdAu alloy (ΔH_H) and the activation energy for diffusion of H in the alloy (E_D). Essentially, the two components of E_act have opposite signs that counteract each other and cause a non-linear trend with increasing Au compositions.

• Research Organization: Colorado School of Mines, Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Fossil Energy (FE); Praxair, Inc
• Grant/Contract Number: FE0004908
• OSTI ID: 1538814
• Alternate ID(s): OSTI ID: 1549207
• Journal Information: Separation and Purification Technology, Vol. 191, Issue C; ISSN 1383-5866
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
PdAu composite membrane
in situ parameter to judge homogenization
apparent activation energy for hydrogen permeation
high-pressure hydrogen anneal
electroless plating/deposition