Thermodynamics and Kinetics of Platinum Dissolution from Carbon-Supported Electrocatalysts in Aqueous Media under Potentiostatic and Potentiodynamic Conditions

Ahluwalia, R.K.; Arisetty, Srikanth; Wang, Xiaoping; Wang, Xiaohua; Subbaraman, Ram; Ball, Sarah C.; DeCrane, Stacy; Myers, Deborah J.

doi:10.1149/2.018306jes

Cited by 82 publications

(123 citation statements)

References 31 publications

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“…Thus, one can see the reason why cycling is so detrimental is that one is transitioning to where Pt wants to dissolve thermodynamically and is not yet protected from doing so by the Pt-oxide layer. A more complicated expression can be used for Pt oxide formation, assuming that Pt forms a non-ideal solid solution with the Pt oxides that appear at potentials higher than 0.85 V. 426 Thus, the activity of Pt in Pt-PtOx solid solution was derived from experimental dissolution data as [133] where c Pt2+ is the concentration of Pt 2+ in the perchloric-acid solution. This model was expanded for use on catalyst-coated membranes and related to accelerated stress tests.…”

Section: 142mentioning

confidence: 99%

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

Weber

Borup

Darling³

et al. 2014

J. Electrochem. Soc.

509

394

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Polymer-electrolyte fuel cells are a promising energy-conversion technology. Over the last several decades significant progress has been made in increasing their performance and durability, of which continuum-level modeling of the transport processes has played an integral part. In this review, we examine the state-of-the-art modeling approaches, with a goal of elucidating the knowledge gaps and needs going forward in the field. In particular, the focus is on multiphase flow, especially in terms of understanding interactions at interfaces, and catalyst layers with a focus on the impacts of ionomer thin-films and multiscale phenomena. Overall, we highlight where there is consensus in terms of modeling approaches as well as opportunities for further improvement and clarification, including identification of several critical areas for future research. Fuel cells may become the energy-delivery devices of the 21 st century. Although there are many types of fuel cells, polymer-electrolyte fuel cells (PEFCs) are receiving the most attention for automotive and small stationary applications. In a PEFC, fuel and oxygen are combined electrochemically. If hydrogen is used as the fuel, it oxidizes at the anode releasing proton and electrons according toThe generated protons are transported across the membrane and the electrons across the external circuit. At the cathode catalyst layer, protons and electrons recombine with oxygen to generate waterAlthough the above electrode reactions are written in single step, multiple elementary reaction pathways are possible at each electrode. During the operation of a PEFC, many interrelated and complex phenomena occur. These processes include mass and heat transfer, electrochemical reactions, and ionic and electronic transport. * Electrochemical Society Active Member. z E-mail: azweber@lbl.govOver the last several decades significant progress has been made in increasing PEFC performance and durability. Such progress has been enabled by experiments and computation at multiple scales, with the bulk of the focus being on optimizing and discovering new materials for the membrane-electrode-assembly (MEA), composed of the proton-exchange membrane (PEM), catalyst layers, and diffusionmedia (DM) backing layers. In particular, continuum modeling has been invaluable in providing understanding and insight into processes and phenomena that cannot be resolved or uncoupled through experiments. While modeling of the transport and related phenomena has progressed greatly, there are still some critical areas that need attention. These areas include modeling the catalyst layer and multiphase phenomena in the PEFC porous media.While there have been various reviews over the years of PEFC modeling 1-7 and issues, [8][9][10][11][12][13][14] as well as numerous books and book chapters, there is a need to examine critically the field in terms of what has been done and what needs to be done. This review serves that purpose with a focus on transport modeling of PEFCs. This is not meant to be an exhaustive review...

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Section: 142mentioning

confidence: 99%

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

Weber

Borup

Darling³

et al. 2014

J. Electrochem. Soc.

509

394

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“…[27][28][29][30][31][32][33][34] As an extension of our previous work, 5 we consider a non-ideal solid solution of Pt and hydroxide/oxides whose composition can be determined by considering the following reactions, which are supported by experimental evidence from the extensive Pt oxidation literature. PtOH…”

Section: Modeling Of Pt Dissolutionmentioning

confidence: 99%

Potential Dependence of Pt and Co Dissolution from Platinum-Cobalt Alloy PEFC Catalysts Using Time-Resolved Measurements

Ahluwalia

Papadias

Kariuki

et al. 2018

J. Electrochem. Soc.

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An electrochemical flow cell system with catalyst-ionomer ink deposited on glassy carbon is used to investigate the aqueous stability of commercial PtCo alloys under cyclic potentials. An on-line inductively coupled plasma-mass spectrometer, capable of real-time measurements, is used to resolve the anodic and cathodic dissolution of Pt and Co during square-wave and triangle-wave potential cycles. We observe Co dissolution at all potentials, distinct peaks in anodic and cathodic Pt dissolution rates above 0.9 V, and potential-dependent Pt and Co dissolution rates. The amount of Pt that dissolves cathodically is smaller than the amount that dissolves anodically if the upper potential limit (UPL) is lower than 0.9 V. At the highest UPL investigated, 1.0 V, the cathodic dissolution greatly exceeds the anodic dissolution. A non-ideal solid solution model indicates that the anodic dissolution can be associated with the electrochemical oxidation of Pt and PtOH to Pt 2+ , and the cathodic dissolution to electrochemical reduction of a higher Pt oxide, PtO x (x > 1), to Pt 2+ . Pt also dissolves oxidatively during the cathodic scans but in smaller amounts than due to the reductive dissolution of PtO x . The relative amounts Pt dissolving oxidatively as Pt and PtOH depend on the potential cycle and UPL.

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“…Surface oxides decrease the activity of oxygen reduction reaction 2 but inhibit the Pt dissolution. 3 Hence, adjusting the amount of oxide in an appropriate range during the operation of PEFCs is essential for balancing the performance and durability.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Oxide Formation and Reduction at Pt Catalyst in Polymer Electrolyte Fuel Cells

Suzuki

Morimoto

2016

Electrochemistry

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The rates of oxide formation and reduction at platinum catalyst in polymer electrolyte fuel cells were measured potentiostatically with various potential histories to reveal the kinetics of the reactions. Reaction rates during potential holds after an anodic or a cathodic sweep were examined as a function of potential and PtOH-equivalent oxide coverage. At 500 and 600 mV vs. RHE, the oxide coverage increased or decreased with increasing time depending on the potential history; this result indicates that the surfaces with different potential histories have different surface states. Oxide reduction rates were compared by changing potential and duration for oxide formation to attain the same coverage before the reduction. Oxide formed at a higher potential for a shorter period of time was easier to reduce than oxide formed at a lower potential for a longer period of time. This indicates that the oxide-formation potential and/or oxide-formation time are factors to determine the oxide reduction rate.

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Thermodynamics and Kinetics of Platinum Dissolution from Carbon-Supported Electrocatalysts in Aqueous Media under Potentiostatic and Potentiodynamic Conditions

Cited by 82 publications

References 31 publications

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

Potential Dependence of Pt and Co Dissolution from Platinum-Cobalt Alloy PEFC Catalysts Using Time-Resolved Measurements

Kinetics of Oxide Formation and Reduction at Pt Catalyst in Polymer Electrolyte Fuel Cells

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