Probing the Structure of Operating Fuel Cell Cathode Catalysts using XAS

Hudson, Sarah L.; Ball, Sarah C.; Blaney, Katie B.; Chouchelamane, Gael Henri; Fiddy, Steven G.; Harvey, Ian; Sivasubramaniamb, Prabalini; Tessier, Béatrice; Theobald, Brian; Thompsett, David; Russell, Andrea E.

doi:10.1149/1.2981980

Cited by 5 publications

(4 citation statements)

References 22 publications

(36 reference statements)

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“…Our theoretical result on Dy O + Dy OH explains the recent experimental results by an in situ XAS study on a membrane electrode assembly (MEA) performed by Hudson et al well. 76 In this experiment, the coordination number of the O atom in the 1st shell of neighbors of Pt increases by changing the atmosphere from N 2 to O 2 at a cell voltage of 0.6 V, but the increase is very small at a cell voltage of 0.9 V.…”

Section: Current Density and Surface Coverages In O 2 Atmospherementioning

confidence: 73%

First principles based mean field model for oxygen reduction reaction

Jinnouchi

Kodama

Hatanaka

et al. 2011

Phys. Chem. Chem. Phys.

116

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A first principles-based mean field model was developed for the oxygen reduction reaction (ORR) taking account of the coverage- and material-dependent reversible potentials of the elementary steps. This model was applied to the simulation of single crystal surfaces of Pt, Pt alloy and Pt core-shell catalysts under Ar and O(2) atmospheres. The results are consistent with those shown by past experimental and theoretical studies on surface coverages under Ar atmosphere, the shape of the current-voltage curve for the ORR on Pt(111) and the material-dependence of the ORR activity. This model suggests that the oxygen associative pathway including HO(2)(ads) formation is the main pathway on Pt(111), and that the rate determining step (RDS) is the removal step of O(ads) on Pt(111). This RDS is accelerated on several highly active Pt alloys and core-shell surfaces, and this acceleration decreases the reaction intermediate O(ads). The increase in the partial pressure of O(2)(g) increases the surface coverage with O(ads) and OH(ads), and this coverage increase reduces the apparent reaction order with respect to the partial pressure to less than unity. This model shows details on how the reaction pathway, RDS, surface coverages, Tafel slope, reaction order and material-dependent activity are interrelated.

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Section: Current Density and Surface Coverages In O 2 Atmospherementioning

confidence: 73%

First principles based mean field model for oxygen reduction reaction

Jinnouchi

Kodama

Hatanaka

et al. 2011

Phys. Chem. Chem. Phys.

116

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“…Recently, several groups have reported in situ studies of proton exchange membrane fuel cells (PEMFCs) incorporating Pt nanoparticle ORR catalysts. − All of these studies utilized a two-electrode configuration incorporating a Pd anode and a cathode composed of Pt/C catalyst dispersed on a carbon support. The results obtained from these studies vary considerably and in some instances the conclusions are inconsistent.…”

Section: Introductionmentioning

confidence: 99%

In Situ Structural Characterization of Platinum Dendrimer-Encapsulated Oxygen Reduction Electrocatalysts

2012

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In situ electrochemical extended X-ray absorption fine structure (EXAFS) was used to evaluate the structure of Pt dendrimer-encapsulated nanoparticles (DENs) during the oxygen reduction reaction (ORR). The DENs contained an average of just 225 atoms each. The results indicate that the Pt coordination number (CN) decreases when the electrode potential is moved to positive values. The results are interpreted in terms of an ordered core, disordered shell model. The structure of the DENs is not significantly impacted by the presence of dioxygen, but other electrogenerated species may have a significant impact on nanoparticle structure.

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“…To correlate the structural insights provide by XAS with catalytic activity requires the study of fuel cell catalysts operando under realistic fuel cell operating conditions (7)(8). This has been achieved by building a specially adapted fuel cell (9).…”

mentioning

confidence: 99%

“…Conducting such time resolved experiments required further modification to our previously reported cell design (9). The cell design will be discussed as will the challenges associated with collection of XAS with milli second time resolution (10).…”

mentioning

confidence: 99%