Abstract
Since trace amounts of CO in H2 gas produced by steam reforming of methane causes severe poisoning of Pt-based catalysts in polymer electrolyte membrane fuel cells (PEMFCs), research has been mainly devoted to exploring CO-tolerant catalysts. To test the electrochemical property of CO-tolerant catalysts, chronoamperometry is widely used under a CO/H2 mixture gas atmosphere as an essential method. However, in most cases of catalysts with high CO tolerance, the conventional chronoamperometry has difficulty in showing the apparent performance difference. In this study, we propose a facile and precise test protocol to evaluate the CO tolerance via a combination of short-term chronoamperometry and a hydrogen oxidation reaction (HOR) test. The degree of CO poisoning is systematically controlled by changing the CO adsorption time. The HOR polarization curve is then measured and compared with that measured without CO adsorption. When the electrochemical properties of PtRu alloy catalysts with different atomic ratios of Pt to Ru are investigated, contrary to conventional chronoamperometry, these catalysts exhibit significant differences in their CO tolerance at certain CO adsorption times. The present work will facilitate the development of catalysts with extremely high CO tolerance and provide insights into the improvement of electrochemical methods.
Highlights
Polymer electrolyte membrane fuel cells (PEMFCs) that use hydrogen (H2) as a fuel have attracted increasing research attention as the most promising next-generation power sources because of an eco-friendly reaction mechanism and high power density [1,2,3]
To emphasize the applicable feasibility of the test protocol for carbon monoxide (CO) tolerance measurement, we compared the electrochemical properties of two representative carbon-supported PtRu (Pt1Ru1/C and Pt1Ru3/C) alloy catalysts composed of different atomic ratios of Pt to Ru
The hydrogen oxidation reaction (HOR) polarization curve measured in the last step can be compared with that measured in a pure H2 atmosphere without CO adsorption (0 s) to corroborate the CO tolerance
Summary
Polymer electrolyte membrane fuel cells (PEMFCs) that use hydrogen (H2) as a fuel have attracted increasing research attention as the most promising next-generation power sources because of an eco-friendly reaction mechanism and high power density [1,2,3]. H2 is produced by steam reforming of methane gas, and the produced H2 gas contains trace amounts of carbon monoxide (CO) of 10–100 ppm [4,5] This small amount of carbon monoxide is sufficient to cause detrimental effects on Pt catalysts widely used in PEMFCs, causing a tremendous suppression in their catalytic performance [6,7]. To alleviate the effect of CO poisoning, various strategies have been adopted, including alloying of Pt with other transition metals, such as Ru, Fe, and Co, formation of core-shell structures, and modification of support materials [8,9,10,11] Among these strategies, the alloying of Pt with transition metals has been regarded as an efficient way to enhance the CO tolerance of Pt-based catalysts. PtRu catalysts have exhibited interesting electrochemical properties towards various anodic reactions, such as methanol and CO oxidation reactions, due to bi-functional and ligand effects, resulting in even higher CO tolerance in the hydrogen oxidation reaction (HOR) using reformed H2 gas [12,13,14,15,16]
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