Abstract:A one-dimensional model is developed and validated to study platinum degradation and the subsequent electrochemical surface area (ECA) loss in the cathode catalyst layer (CL) of polymer electrolyte fuel cells (PEFCs). The model includes two mechanisms of Pt degradation: Ostwald ripening on carbon support and Pt dissolution-re-precipitation through the ionomer phase. Impact of H 2 | N 2 or H 2 | Air operation, operating temperature, and relative humidity (RH) on Pt degradation during voltage cycling is explored… Show more
“…The overall ECA evolutions and PSDs at various positions of CCL were compared with experimental data in their study. 53 The 1D Pt degradation model of Li et al 53 describes the Ostwald ripening and Pt dissolution-re-precipitation across the CCL, which is similar to the Pt degradation model proposed by Takeshita et al 54 However, by incorporating the temperature-dependent kinetic equations of Holby and Morgan 50 and developing an additional 55 The non-uniform Pt degradation causes non-uniform ECA across the PEFC CCL in the through-plane direction as introduced. This non-uniform ECA distribution of the degraded PEFC CCL could reshape the current density distributions in PEFC CCLs.…”
mentioning
confidence: 97%
“…In a recent study, Holby and Morgan 50 applied much finer Pt particle size bins in their Pt degradation model and specifically discussed the impacts of the Pt PSD shape on the speed of Pt degradation. Based on the kinetic equations developed by Holby and Morgan, 50 Li et al 53 developed a 1D Pt degradation model to investigate the non-uniform Pt degradation and predict the non-uniform ECA loss across the CCL. The overall ECA evolutions and PSDs at various positions of CCL were compared with experimental data in their study.…”
Pt degradation is one of the most important aging mechanisms that control the lifespan of automotive polymer electrolyte fuel cells (PEFCs). The consequence of Pt degradation is loss of the electrochemical active surface area (ECA) in cathode catalyst layers (CCLs) of PEFCs. The reduction of ECA increases not only the activation overpotential through reducing sites of oxygen reduction reaction (ORR) kinetics but also the mass transport loss through causing an additional micro-scale oxygen transport resistance in the ionomer film surrounding Pt particles. In this study, a 1D physics-based Pt degradation submodel is coupled into the transient M2 model to study the non-uniform Pt degradation and its impacts on long-term PEFC performance. The performance loss of a low Pt-loading PEFC with Pt degradation, the interactions of Pt degradation with the micro-scale transport resistance, the cause and consequence of non-uniform Pt degradation, as well as a strategy of raising lower current density in current cycling test are quantified. This Pt degradation model is demonstrated to be an effective approach to better understand Pt degradation, performance loss caused by Pt degradation, and mitigation strategies to alleviate Pt degradation, all important for achieving excellent durability of PEFCs.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.203.192.85 Downloaded on 2017-01-23 to IP F172 Journal of The Electrochemical Society, 164 (2) F171-F179 (2017) ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.203.192.85 Downloaded on 2017-01-23 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.203.192.85 Downloaded on 2017-01-23 to IP Journal of The Electrochemical Society, 164 (2) F171-F179 (2017) ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.203.192.85 Downloaded on 2017-01-23 to IP
“…The overall ECA evolutions and PSDs at various positions of CCL were compared with experimental data in their study. 53 The 1D Pt degradation model of Li et al 53 describes the Ostwald ripening and Pt dissolution-re-precipitation across the CCL, which is similar to the Pt degradation model proposed by Takeshita et al 54 However, by incorporating the temperature-dependent kinetic equations of Holby and Morgan 50 and developing an additional 55 The non-uniform Pt degradation causes non-uniform ECA across the PEFC CCL in the through-plane direction as introduced. This non-uniform ECA distribution of the degraded PEFC CCL could reshape the current density distributions in PEFC CCLs.…”
mentioning
confidence: 97%
“…In a recent study, Holby and Morgan 50 applied much finer Pt particle size bins in their Pt degradation model and specifically discussed the impacts of the Pt PSD shape on the speed of Pt degradation. Based on the kinetic equations developed by Holby and Morgan, 50 Li et al 53 developed a 1D Pt degradation model to investigate the non-uniform Pt degradation and predict the non-uniform ECA loss across the CCL. The overall ECA evolutions and PSDs at various positions of CCL were compared with experimental data in their study.…”
Pt degradation is one of the most important aging mechanisms that control the lifespan of automotive polymer electrolyte fuel cells (PEFCs). The consequence of Pt degradation is loss of the electrochemical active surface area (ECA) in cathode catalyst layers (CCLs) of PEFCs. The reduction of ECA increases not only the activation overpotential through reducing sites of oxygen reduction reaction (ORR) kinetics but also the mass transport loss through causing an additional micro-scale oxygen transport resistance in the ionomer film surrounding Pt particles. In this study, a 1D physics-based Pt degradation submodel is coupled into the transient M2 model to study the non-uniform Pt degradation and its impacts on long-term PEFC performance. The performance loss of a low Pt-loading PEFC with Pt degradation, the interactions of Pt degradation with the micro-scale transport resistance, the cause and consequence of non-uniform Pt degradation, as well as a strategy of raising lower current density in current cycling test are quantified. This Pt degradation model is demonstrated to be an effective approach to better understand Pt degradation, performance loss caused by Pt degradation, and mitigation strategies to alleviate Pt degradation, all important for achieving excellent durability of PEFCs.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.203.192.85 Downloaded on 2017-01-23 to IP F172 Journal of The Electrochemical Society, 164 (2) F171-F179 (2017) ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.203.192.85 Downloaded on 2017-01-23 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.203.192.85 Downloaded on 2017-01-23 to IP Journal of The Electrochemical Society, 164 (2) F171-F179 (2017) ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.203.192.85 Downloaded on 2017-01-23 to IP
“…It has been observed in the literature that different amounts of Pt dissolution at inlet and outlet and different distributions of Pt causes significant spatially-varying ECSA loss [33,47]. This indicates that, in order to reliably model the spatially resolved cell degradation, other local degradation mechanisms must be considered.…”
Section: Discussionmentioning
confidence: 99%
“…It has been shown in the literature that catalyst layer structure and the Pt transport in catalyst layer (CL) give more detailed insights into the volume-specific electrochemistry and species transport, which affect the cell performance, specially in the case of low Pt loading conditions (ca. 0.025 mg/cm 2 ) [32,33], but in this work, we decided to use a reduced complexity model with a uniform distribution of Pt (loading of 0.15 mg/cm 2 ) along the CL. Further, we hypothesize that the Pt dissolution in the CL is significantly influenced by the local cell parameters such as cell voltage, oxygen, and water concentration, mainly originating from the transport in the GDL and the membrane.…”
One of the bottlenecks hindering the usage of polymer electrolyte membrane fuel cell technology in automotive applications is the highly load-sensitive degradation of the cell components. The cell failure cases reported in the literature show localized cell component degradation, mainly caused by flow-field dependent non-uniform distribution of reactants. The existing methodologies for diagnostics of localized cell failure are either invasive or require sophisticated and expensive apparatus. In this study, with the help of a multiscale simulation framework, a single polymer electrolyte membrane fuel cell (PEMFC) model is exposed to a standardized drive cycle provided by a system model of a fuel cell car. A 2D multiphysics model of the PEMFC is used to investigate catalyst degradation due to spatio-temporal variations in the fuel cell state variables under the highly transient load cycles. A three-step (extraction, oxidation, and dissolution) model of platinum loss in the cathode catalyst layer is used to investigate the cell performance degradation due to the consequent reduction in the electro-chemical active surface area (ECSA). By using a time-upscaling methodology, we present a comparative prediction of cell end-of-life (EOL) under different driving behavior of New European Driving Cycle (NEDC) and Worldwide Harmonized Light Vehicles Test Cycle (WLTC).
“…At the last decade, numerous degradation models have been published [19e43]. Most of the models consider degradation phenomena in a single component of the fuel cell: either in the membrane [21,25,28,29], or in the catalyst layer [20,23,24,26,27,30], or in the gas diffusion layer [22]. There are much less models predicting durability [19,34,35,40e44] or performance [25,33e39] of a complete fuel cell or stack.…”
Available online xxxKeywords: Polymer electrolyte fuel cell Nafion degradation Modelling Computational fluid dynamics Local operating condition a b s t r a c t The paper describes a development of a degradation model, which enables to predict timedependent changes in performance of a polymer electrolyte fuel cell. The developed model consists of two main parts: 1) a new semi-empirical model taking into account changes in physico-chemical properties of a polymer electrolyte membrane operating in the fuel cell, 2) a validated CFD model computing the 3D performance of the cell. In the semi-empirical model, the degradation rates of the membrane thickness and conductivity depend on the oxygen crossover rate. The acid group concentration is calculated from the membrane conductivity based on the percolation theory approach. The gas diffusion coefficients are modelled empirically as a function of the membrane thickness. The model of the membrane degradation is coupled with the CFD model and applied to analyse the cell behaviour as a function of time. The simulation shows that the cell current density decreases faster with lowering relative humidity and increasing temperature. The in-plane degradation of the membrane is non-uniform and depends on the local operating condition.
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