Operando Time-Resolved X-ray Absorption Fine Structure Study for Surface Events on a Pt₃Co/C Cathode Catalyst in a Polymer Electrolyte Fuel Cell during Voltage-Operating Processes

Abstract

The structural kinetics of surface events on a Pt 3 Co/C cathode catalyst in a polymer electrolyte fuel cell (PEFC) was investigated by operando time-resolved X-ray absorption fine structure (XAFS) with a time resolution of 500 ms. The rate constants of electrochemical reactions, the changes in charge density on Pt, and the changes in the local coordination structures of the Pt 3 Co alloy catalyst in the PEFC were successfully evaluated during fuel-cell voltage-operating processes. Significant time lags were observed between the electrochemical reactions and the structural changes in the Pt 3 Co alloy catalyst. The rate constants of all the surface events on the Pt 3 Co/C catalyst were significantly higher than those on the Pt/ C catalyst, suggesting the advantageous behaviors (cell performance and catalyst durability) on the Pt 3 Co alloy cathode catalyst.

Synthesis and Electrochemical Evaluation of Carbon Supported Pt-Co Bimetallic Catalysts Prepared by Electroless Deposition and Modified Charge Enhanced Dry Impregnation

“…Sample B exhibited a specific activity of 0.0587 mA/m 2 Pt, 7.5 times greater than the Pt/C catalyst (0.0078 mA/m 2 Pt). The results of the current work, where higher platinum mass normalized activities and electrochemical surface activities are observed for the bimetallic ED catalysts, are in line with prior studies [6][7][8]53]. The alloying of Pt with Co enhanced the catalyst properties of Pt that are beneficial for ORR applications; Pt charge density increases either by electronic interaction with Co and/or lattice contraction (strain) by substitution of Co into the Pt lattice.…”

Key Factors Affecting the Performance and Durability of Cathode Electrocatalysts in Polymer Electrolyte Fuel Cells Characterized by In Situ Real Time and Spatially Resolved XAFS Techniques

“…The white line peak heights of Pt 3 Co/C and Pt 3 Ni/C at 0.4 V were less than that for Pt/C, indicating electron transfer from Co or Ni to Pt. This is similar to our previous results for a Pt 3 Co/C electrocatalyst with 6 mg-PtCo cm -2 [15]. As for the structural parameters Fig.…”

“…have extensively been studied [3][4][5][6][7][8][9][10][11][12][13], but they are difficult to observe the dynamic and spatial behavior and transformation of Pt nanoparticles under PEFC operating conditions. In situ time-resolved X-ray absorption fine structure (XAFS) techniques are very powerful for in situ/ operando investigation of the local coordination structures and oxidation states of supported nanoparticle catalysts under working conditions particularly in such complex systems as PEFCs, involving Pt valence change and Pt-O/ Pt-Pt bonds transformation [14][15][16][17][18][19][20]. These key reaction processes, which regulate the durability of PEFCs as well as the ORR activity, may occur heterogeneously in the space of the cathode layer due to the spatially heterogeneous property and distribution of Pt nanoparticles and carbon supports and the microscopically non-uniform potentials loaded in the cathode layer under PEFC potential operations [21].…”

X-ray absorption fine structure spectroscopy in nanomaterials

“…The real-time XAFS measurements monitoring the structural transformation of active Re 10 clusters to inactive Re monomers suggested the direct transformation of Re 10 cluster to the Re monomers, showing a first order reaction to the Re 10 cluster quantity. Besides, they used the time-resolved XAFS with a 0.5 s time resolution to study the structural kinetics of surface events on a Pt 3 Co/C cathode catalyst in a polymer electrolyte fuel cell under operando conditions [104].…”