PdAgAu alloy with high resistance to corrosion by H2S

BRAUN FERNANDO; JAMES B. MILLER; ANDREW J. GELLMAN; ANA M. TARDITI; BENOIT FLEUTOT; PETRO KONDRATYUK; LAURA M. CORNAGLIA

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2012 vol. 37 p. 18547 - 18555

0360-3199

PdAgAu alloy films were prepared on porous stainless steel supports by sequential electrolessdeposition. Two specific compositions, Pd83Ag2Au15 and Pd74Ag14Au12, were studiedfor their sulfur tolerance. The alloys and a reference Pd foil were exposed to 1000H2S/H2 at623 K for periods of 3 and 30 h. The microstructure, morphology and bulk composition ofboth non-exposed and H2S-exposed samples were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). XRDand SEM analysis revealed time-dependent growth of a bulk Pd4S phase on the Pd foilduring H2S exposure. In contrast, the PdAgAu ternary alloys displayed the same FCCstructure before and after H2S exposure. In agreement with the XRD and SEM results, sulfurwas not detected in the bulk of either ternary alloy samples by EDS, even after 30 h of H2Sexposure. X-ray photoelectron spectroscopy (XPS) depth profiles were acquired for bothPdAgAu alloys after 3 and 30 h of exposure to characterize sulfur contamination near theirsurfaces. Very low S 2p and S 2s XPS signals were observed at the top-surfaces of thePdAgAu alloys, and those signals disappeared before the etch depth reached w10 nm, evenfor samples exposed to H2S for 30 h. The depth profile analyses also revealed silver and goldsegregation to the surface of the alloys; preferential location of Au on the alloys surfacemay be related to their resistance to bulk sulfide formation. In preliminary tests, a PdAgAualloy membrane displayed higher initial H2 permeability than a similarly prepared pure Pdsample and, consistent with resistance to bulk sulfide formation, lower permeability loss inH2S than pure Pd.