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

Yoshiyuki Ogihara,Hiroyuki Uchida,Akihiro Iiyama,Takahiro Matsumoto,Hiroshi Yano,Donald Tryk

doi:10.3390/catal7010008

Yoshiyuki Ogihara, Hiroyuki Uchida + Show 4 more

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https://doi.org/10.3390/catal7010008

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Abstract

The CO-tolerance mechanism of a carbon-supported Pt-Fe alloy catalyst with two atomic layers of stabilized Pt-skin (Pt2AL–PtFe/C) was investigated, in comparison with commercial Pt2Ru3/C (c-Pt2Ru3/C), by in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy in 0.1 M HClO4 solution at 60 °C. When 1% CO (H2-balance) was bubbled continuously in the solution, the hydrogen oxidation reaction (HOR) activities of both catalysts decreased severely because the active sites were blocked by COad, reaching the coverage θCO ≈ 0.99. The bands in the IR spectra observed on both catalysts were successfully assigned to linearly adsorbed CO (COL) and bridged CO (COB), both of which consisted of multiple components (COL or COB at terraces and step/edge sites). The Pt2AL–PtFe/C catalyst lost 99% of its initial mass activity (MA) for the HOR after 30 min, whereas about 10% of the initial MA was maintained on c-Pt2Ru3/C after 2 h, which can be ascribed to a suppression of linearly adsorbed CO at terrace sites (COL, terrace). In contrast, the HOR activities of both catalysts with pre-adsorbed CO recovered appreciably after bubbling with CO-free pure H2. We clarify, for the first time, that such a recovery of activity can be ascribed to an increased number of active sites by a transfer of COL, terrace to COL, step/edge, without removal of COad from the surface. The Pt2AL–PtFe/C catalyst showed a larger decrease in the band intensity of COL, terrace. A possible mechanism for the CO-tolerant HOR is also discussed.

Highlights

For the applications of fuel cell vehicles (FCVs) and stationary cogeneration systems (FC-CG), polymer electrolyte fuel cells (PEFCs) have been actively developed
Far, Pt-Ru alloy anode catalysts have been employed for the hydrogen oxidation reaction (HOR) to lessen the poisoning by low concentrations of CO contained in the reformate
We have reported our research on the effect of the non-noble metal species M (M = Fe, Co, Ni) in Pt2AL –Pt-M/C on CO-tolerance and the robustness by the use of channel flow electrode (CFE) method in 0.1 M HClO4

Summary

Introduction

For the applications of fuel cell vehicles (FCVs) and stationary cogeneration systems (FC-CG), polymer electrolyte fuel cells (PEFCs) have been actively developed. Because the CO-tolerant HOR mass activity (based on the mass of both noble metals, Pt and Ru) and durability of c-Pt2 Ru3 /C are not sufficient, it is very important to develop novel anode catalysts, which would simplify the system, leading to cost reduction. As the support or co-catalyst for Pt-Ru alloys, the use of metal oxide materials has been effective in increasing the CO-tolerance [2,3,4,5,6,7]. We have reported our research on the effect of the non-noble metal species M (M = Fe, Co, Ni) in Pt2AL –Pt-M/C on CO-tolerance and the robustness by the use of channel flow electrode (CFE) method in 0.1 M HClO4. For the first time, demonstrate that the recovery of the HOR activity that occurs on these catalysts when changing the gas from CO/H2 to pure H2 can be ascribed to the mobility of adsorbed CO, resulting in increased numbers of active sites

FTIR Analysis of CO Adsorption on Catalysts

20 Adsorption

FTIR Analysis of Recovery of HOR Activity on CO-Adsorbed Catalysts

Changes

Experimental Section

Conclusions