Degradation of Bimetallic Model Electrocatalysts ___ an in situ XAS Study

Journal Article · Wed Jun 22 04:00:00 EDT 2011 · Submitted to Angewandte Chemie International Edition

DOI:https://doi.org/10.1002/anie.201101620· OSTI ID:1017211

Friebel, Daniel

One of the major challenges in the development of clean energy fuel cells is the performance degradation of the electrocatalyst, which, apart from poisoning effects, can suffer from corrosion due to its exposure to a harsh environment under high potentials. In this communication, we demonstrate how interactions of Pt with a transition metal support affect not only, as commonly intended, the catalytic activity, but also the reactivity of Pt towards oxide formation or dissolution. We use two well-defined single-crystal model systems, Pt/Rh(111) and Pt/Au(111) and a unique x-ray spectroscopy technique with enhanced energy resolution to monitor the potential-dependent oxidation state of Pt, and find two markedly different oxidation mechanisms on the two different substrates. This information can be of great significance for future design of more active and more stable catalysts. We have studied the potential-induced degradation of Pt monolayer model electrocatalysts on Rh(111) and Au(111) single-crystal substrates. The anodic formation of Pt oxides was monitored using in situ high energy resolution fluorescence detection x-ray absorption spectroscopy (HERFD XAS). Although Pt was deposited on both substrates in a three-dimensional island growth mode, we observed remarkable differences during oxide formation that can only be understood in terms of strong Pt-substrate interactions throughout the Pt islands. Anodic polarization of Pt/Rh(111) up to +1.6 V vs. RHE (reversible hydrogen electrode) leads to formation an incompletely oxidized passive layer, whereas formation of PtO2 and partial Pt dissolution is observed for Pt/Au(111).

• Research Organization: SLAC National Accelerator Laboratory (SLAC)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 1017211
• Report Number(s): SLAC-PUB-14485
• Journal Information: Submitted to Angewandte Chemie International Edition, Journal Name: Submitted to Angewandte Chemie International Edition; ISSN 1433-7851
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
30 DIRECT ENERGY CONVERSION
ABSORPTION SPECTROSCOPY
CATALYSTS
CHEM
MATSCI
CORROSION
DESIGN
DETECTION
DISSOLUTION
ELECTROCATALYSTS
ENERGY RESOLUTION
FLUORESCENCE
FUEL CELLS
HYDROGEN
OXIDATION
OXIDES
POLARIZATION
SUBSTRATES
TRANSITION ELEMENTS
VALENCE
X-RAY SPECTROSCOPY