Oxygen Reduction Reaction Activity of Carbon-Supported Pt-Fe, Pt-Co, and Pt-Ni Alloys with Stabilized Pt-Skin Layers

Abstract

We have prepared carbon-supported Pt-M (M = Fe, Co, and Ni) alloy nanoparticles with uniform size and composition as cathode catalysts for polymer electrolyte fuel cells. In order to protect the underlying Pt-M alloy from dealloying and maintain high mass activity for the oxygen reduction reaction (ORR), two atomic layers of Ptskin (Pt 2AL ) were formed on the Pt-M nanopartcicles. By means of various types of analysis, including X-ray diffraction (XRD), inductively coupled plasma mass analysis (ICP-MS), thermogravimetry (TG), and transmission electron microscopy (TEM), the formation of monodisperse Pt 2AL -Pt-M/C was confirmed. The kinetically-controlled ORR activities (mass activity, MA k , and area-specific activity, j k ) for the ORR at Nafion ® -coated Pt 2AL -Pt-M/C catalysts in O 2 -saturated 0.1 M HClO 4 solution were evaluated by the use of a multi-channel flow double electrode cell at 65°C. It was found that the initial value of MA k at Pt 2AL -PtNi/C was the highest, i.e., 3.3 times higher than that at a commercial catalyst, carbon-supported Pt (c-Pt/C). In contrast, the Pt 2AL -PtCo/C catalyst exhibited superior durability, so that dealloying was almost entirely suppressed, together with a great mitigation of the particle agglomeration after applying 10 4 cycles of potential steps between 0.6 V and 1.0 V.

Oxygen Reduction Activity and Durability of Ordered and Disordered Pt3Co Alloy Nanoparticle Catalysts at Practical Temperatures of Polymer Electrolyte Fuel Cells

“…One of the promising methods for improving the durability, while maintaining high MA k , is the formation of stabilized Pt-skin layers, which we developed recently. 53,54 The formation of stabilized Pt skin layers on the controlled Pt-alloy crystal structure is now in progress in our laboratory.…”

In Situ FTIR Analysis of CO-Tolerance of a Pt-Fe Alloy with Stabilized Pt Skin Layers as a Hydrogen Anode Catalyst for Polymer Electrolyte Fuel Cells

“…% metal loading) was prepared by the use of a high surface area (specific surface area = 780 m 2 ·g −1 ) carbon black support (Denka Co. Ltd., Tokyo, Japan) in the same manner as that described previously [11,20]. A commercial catalyst c-Pt 2 Ru 3 /C (TEC61E54, 50 wt.…”

Research and Development of Highly Active and Durable Electrocatalysts Based on Multilateral Analyses of Fuel Cell Reactions

“…Very recently, we have successfully prepared monodisperse PtCo alloy NPs, having approximately two atomic layers of stabilized Pt skin, dispersed uniformly on graphitized carbon black (GCB) or high-surface-area carbon black (Pt xAL -PtCo/ GCB or Pt xAL -PtCo/C, 1 < x¯2 by more recent analysis). 52,53 Figure 3 shows the variations in MA k at 0.85 V on Pt xAL -PtCo/GCB as a function of log N in potential changes at 65°C, simulating loadcycles and startup/shutdown-cycles of FCVs. The initial MA k for both Pt xAL -PtCo/GCB and PtCo/GCB was a factor of ca.…”

“…Carbon-supported Pt xAL -Pt-M (M = Fe, Co, and Ni) also exhibited superior performances both in the MA k and the durability. 53 A collaborative effort with a catalyst company is under way to establish an industrial preparation method of these new catalysts.…”

“…[37][38][39][40][41][42] Based on these results, new practical catalysts have been synthesized. [43][44][45][46][47][48][49][50][51][52][53][54][55] New catalyst layers or membraneelectrode-assemblies (MEAs) have been developed in order to make the electrocatalysts work effectively under widely varying operating conditions of relative humidity (RH) and temperature. [56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72] Changes in the distribution of the specific resistance in the PEM and oxygen partial pressure at the CL/PEM interface during operation, [73][74][75] as well as the degradation mechanism of the MEAs, 59,63,64,76,77 were also analyzed to feedback information to the syntheses of PEMs and catalysts.…”