Investigation of sulfur poisoning of CNx oxygen reduction catalysts for PEM fuel cells

Deak, Dieter von; Singh, Deepika; Biddinger, Elizabeth J.; King, Jesaiah; Bayram, Burcu; Miller, Jeffrey T.; Ozkan, Umit S.

doi:10.1016/j.jcat.2011.09.027

Cited by 54 publications

(35 citation statements)

References 59 publications

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“…27 In addition, a marked decrease in activity was noted for FeNC catalysts after H 2 S treatment 28 providing evidence that iron is an essential part of the ORR active site in these catalysts unlike CN x catalysts where no decrease in activity was observed after sulfur exposure. 29 Though the above-mentioned studies by our group were significant in highlighting that FeNC and CN x catalysts are indeed two distinct classes of NNMCs and have very different active sites, the actual ORR active sites in both materials continue to be a subject of contention. One of first active site model for FeNC materials was proposed by Dodelet's group where it was suggested that the iron is stabilized by the presence of two pyridinic nitrogen atoms (phenanthroline-type active site).…”

Section: Introductionmentioning

confidence: 93%

CO Poisoning Effects on FeNC and CN_x ORR Catalysts: A Combined Experimental–Computational Study

et al. 2016

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CO poisoning as a probe for oxygen reduction reaction (ORR) active sites was examined on both iron-nitrogen coordinated catalysts supported on carbon (FeNC) and nitrogen-doped carbon nanostructures (CN x ). Rotating disk electrode (RDE) experiments show a partial decrease in the ORR activity of FeNC catalysts after CO exposure and no decrease for CN x catalysts. Diffuse Reflectance Infrared Fourier transform (DRIFT) Spectroscopy experiments after exposure to CO show a peak at 2033 cm -1 (associated with linearly bound CO) on the FeNC catalysts and no peaks associated with adsorbed CO on the CN x catalyst surface. Density functional theory (DFT) calculations incorporating dispersion interactions of the adsorption energy of O 2 and CO were performed on a total of sixteen proposed active sites for the FeNC and CN x catalysts. On CN x , all the sites show weak CO adsorption and only O 2 molecules are expected to adsorb, which matches the experimental observation of no poisoning. Several FeNC sites show CO binding energies similar in strength to that seen for Pt(111), but only two sites, namely FeN 4 /C pyridinic and FeN 4 /C pyrrolic, are found to bind CO stronger than O 2 . DFT results suggest that the partial poisoning (instead of complete poisoning as found on Pt catalysts) observed in experiments is due to only some fraction of the active sites being blocked. DFT-derived CO stretch frequencies on FeNC show a similar redshift as observed in the DRIFTS experiments, which further confirms that the FeNC catalysts adsorb CO while the CN x catalysts only show weak physisorption.

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Section: Introductionmentioning

confidence: 93%

CO Poisoning Effects on FeNC and CN_x ORR Catalysts: A Combined Experimental–Computational Study

et al. 2016

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“…Another approach to gain information about the active site by electrochemical measurements can be achieved by controlled catalyst poisoning where certain poisons, e.g. sulfur 58, 179 or cyanide 180, affect only certain active site structures.…”

Section: Evaluation and Characterization Of Npmcsmentioning

confidence: 99%

“…XAS is another powerful method for characterizing the local atomic structure of NPMCs. It is far more widely used than Mössbauer spectroscopy and both XANES and EXAFS techniques of XAS provide useful information 51, 56, 57, 80, 107, 108, 111, 179. A difficulty in both XAS and Mössbauer spectroscopy characterization is that they are bulk averaging techniques, and that NPMCs oftentimes may contain several different active site structures as well as inactive structures containing the probed element type, which are very challenging to separate from each other.…”

Section: Evaluation and Characterization Of Npmcsmentioning

confidence: 99%

Recent Progress in Synthesis, Characterization and Evaluation of Non‐Precious Metal Catalysts for the Oxygen Reduction Reaction

2016

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The oxygen reduction reaction (ORR) is usually catalyzed by precious metals. As the kinetics of the reaction are sluggish comparatively large amounts of precious metal are needed to achieve satisfactory reaction rates. This results in high cost of technologies utilizing the ORR, like low temperature fuel cells. Recent years have seen tremendous research efforts in the development of non‐precious metal catalysts (NPMCs) with a wide range of newly developed materials resulting in improved catalyst materials, an increased understanding of the ORR mechanism on NPMC materials and better knowledge of the active site structure. Here we summarize the developments from 2011 and onwards with a special focus on carbon‐based NPMCs developed for use in acid environments. We include explicit comparisons of PEMFC measurement results in all referenced studies and detailed information on the physical characterization methods used in various publications.

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“…In spite of well-established differences, the question of the active site and the role of the metal in these two classes of catalysts continues to linger. Additional studies were performed to probe the active site in both materials using H 2 S, a well-known poison [42,43]. Activity loss in iron-based catalysts has been attributed to sulfur for many well-known reactions such as Fisher-Tropsch, water-gas shift, ammonia synthesis, ammonia decomposition and iron carburization [44][45][46][47].…”

Section: Use Of H 2 S Poisoning As a Probementioning

confidence: 99%

Heteroatom-Doped Carbon Nanostructures as Oxygen Reduction Reaction Catalysts in Acidic Media: An Overview

Mamtani

Ozkan

2014

Catal Lett

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This paper provides an overview of the studies that were conducted in our laboratories in the last decade on hetero-atom doped carbon structures as potential oxygen reduction reaction (ORR) catalysts for PEM fuel cells. These studies include evaluating the potential of nitrogen doped carbon nanostructures as cathode catalysts for proton exchange membrane and direct methanol fuel cells and examining the nature of the transition metal used as growth catalysts in synthesis of these materials, through activity and in situ and ex situ characterization experiments. These studies also shed some light on the ongoing debate about the differences and similarities between two classes of materials used for ORR, namely FeNC and CN x catalysts, through activity and stability tests, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, Mössbauer spectroscopy, temperature-programmed techniques and selective poisoning experiments designed to probe the active sites.

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Investigation of sulfur poisoning of CNx oxygen reduction catalysts for PEM fuel cells

Cited by 54 publications

References 59 publications

CO Poisoning Effects on FeNC and CN_x ORR Catalysts: A Combined Experimental–Computational Study

CO Poisoning Effects on FeNC and CN_x ORR Catalysts: A Combined Experimental–Computational Study

Recent Progress in Synthesis, Characterization and Evaluation of Non‐Precious Metal Catalysts for the Oxygen Reduction Reaction

Heteroatom-Doped Carbon Nanostructures as Oxygen Reduction Reaction Catalysts in Acidic Media: An Overview

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Investigation of sulfur poisoning of CNx oxygen reduction catalysts for PEM fuel cells

Cited by 54 publications

References 59 publications

CO Poisoning Effects on FeNC and CNx ORR Catalysts: A Combined Experimental–Computational Study

CO Poisoning Effects on FeNC and CNx ORR Catalysts: A Combined Experimental–Computational Study

Recent Progress in Synthesis, Characterization and Evaluation of Non‐Precious Metal Catalysts for the Oxygen Reduction Reaction

Heteroatom-Doped Carbon Nanostructures as Oxygen Reduction Reaction Catalysts in Acidic Media: An Overview

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CO Poisoning Effects on FeNC and CN_x ORR Catalysts: A Combined Experimental–Computational Study

CO Poisoning Effects on FeNC and CN_x ORR Catalysts: A Combined Experimental–Computational Study