Highly Active, CO-Tolerant, and Robust Hydrogen Anode Catalysts: Pt–M (M = Fe, Co, Ni) Alloys with Stabilized Pt-Skin Layers

Abstract

The electrocatalytic activity for the hydrogen oxidation reaction (HOR) in the presence of 1000 ppm of CO has been investigated on a series of binary Pt alloy catalysts Pt–M (M = Fe, Co, Ni), having two atomic layers of stabilized Pt skin (Pt2AL), supported on carbon black (Pt2AL–PtFe/C, Pt2AL–PtCo/C, and Pt2AL–PtNi/C) in 0.1 M HClO4 solution at 70 and 90 °C. It was found that Pt2AL–PtFe/C exhibited the highest CO-tolerant HOR activity (with respect to the area-specific activity j s and the mass activity MA), followed by Pt2AL–PtCo/C and Pt2AL–PtNi/C. Such an order of the j s values for the HOR with and without adsorbed CO can be correlated with density functional theory calculations, which have enabled us to propose a mechanism for the HOR on these surfaces. The apparent values of MA for the HOR on Pt2AL–PtFe/C at 20 mV vs RHE were 2–3 times larger than those for the conventional commercial catalyst c-Pt2Ru3/C over the whole CO coverage range from 0 to 0.7 at 70 and 90 °C. For an accelerated durability test simulating air exposure (2500 potential cycles between 0.02 and 0.95 V), the apparent j s values for the CO-tolerant HOR on these Pt-skin catalysts were maintained completely, indicating that the dealloying of M components was virtually suppressed, whereas a significant reduction in j s was observed for c-Pt2Ru3/C. A great mitigation of the particle agglomeration was also a highly attractive property of our catalysts in comparison with the commercial catalysts c-Pt/C and c-Pt2Ru3/C.

Electrochemical Oxidation of Hydrolyzed Poly-Oxymethylene-Dimethylether by Pt and PtRu Catalysts on Ta-Doped SnO2Supports for Direct Oxidation Fuel Cells

“…It is well known that the CO coverage and/or adsorption strength on Pt and Pt alloys depend upon various structural and electronic factors. This has been documented experimentally and theoretically in previous papers, for pure Pt, and for Pt-M alloys, [42][43][44][45] and thus, it has been found that the apparent CO coverage on Pt and Pt-M surfaces (θ, %) does not always reach 100%. [37][38][39][40][41] Therefore, in the present work, we have simply compared the catalytic behavior among them based on the Pt weight, or the geometric electrode surface area of the RDE, and the MEAs loaded with the same amounts of Pt.…”

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

“…Such an enhancement factor in the MA for the HOR of pure H2 on the Pt2AL-PtFe/C was smaller than that (ca. 2.5 times) measured in the CFE at 70 and 90 °C [10]. This is ascribed with certainty to the fact that it is difficult for all of the catalyst particles to work effectively for the HOR, because the thickness of the catalyst layer loaded on the ATR prism corresponded to about 6.5 monolayers of the carbon black particles (to increase the signal/noise ratio of the IR spectrum), whereas the amount of the catalyst loaded in the CFE cell was ca.…”

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

“…They showed superlative CO-tolerance and high robustness with respect to air exposure at 70 to 90°C. 54,55 The Pt xAL -PtFe/C catalyst exhibited the highest CO-tolerant HOR activity ( j s and MA), followed by Pt xAL -PtCo/C and Pt xAL -PtNi/C. In situ ATR-FTIR, 22 in situ X-ray absorption spectroscopy, 118 and DFT calculations 55 clearly demonstrated the weakening of CO adsorption on the Pt xAL .…”

“…Recently, non-fluorinated hydrocarbon (HC) electrolyte membranes have been developed to reduce cost, to elevate the operating temperature, and to avoid environmental pollution due to fluoride on disposal. Specifically, the elevation of operating temperature (² 100°C) leads to a significant cost reduction by increases in the MA values for the ORR 40 of the cathode catalysts and the CO-tolerant HOR of the anode catalysts, 36,55 together with a down-sizing of the heat exchanger (radiator) in FCVs (due to increased ¦T ).…”

“…[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.…”