Deleterious effects of interim cyclic voltammetry on Pt/carbon black catalyst degradation during start-up/shutdown cycling evaluation

Park, Young-Chul; Kakinuma, Katsuyoshi; Uchida, Makoto; Uchida, Hiroyuki; Watanabe, Masahiro

doi:10.1016/j.electacta.2013.12.120

Cited by 85 publications

(71 citation statements)

References 41 publications

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“…11,25,26,29 The ECSA loss due to increased number of ADT cycles shows initially a fast decay during the first 1000 perturbation cycles, followed by a gradual loss over an extended number of cycles. 14,30 To more fully track the decay process it is logical to increase the assessment frequency during the first several thousand ADT perturbations, although as shown herein the effects from this more frequent analysis would not correlate to actual automotive PEMFC life. Park et al performed triangular wave ADTs between 1.0 V and 1.5 V at 500 mV sec −1 and observed an accelerated decay dependence with increased frequency of ECSA assessment due to depassivation of the oxide layer covering the carbon support resulting in sever carbon corrosion.…”

Section: F1176mentioning

confidence: 99%

“…13,21,22 The classical testing protocols used to study cathode catalyst durability are fast potential variations from an Upper Potential Limit (UPL) ranging from 0.9 V to 1.2 V to a Lower Potential Limit (LPL) of 0.6 V to simulate cathode potential variations during transient operation (idle-to-peak) or up to an UPL of 1.2-1.5 V for startup/shutdown cycles simulation. [12][13][14]16,[23][24][25][26] All potentials herein are verses a Reversible Hydrogen Electrode (RHE) reference. The ECSA is typically periodically assessed during the ADT to correlate to performance losses.…”

Section: F1176mentioning

confidence: 99%

“…12,14,15 However, the participation of multiple factors influencing the stability of the cathode catalyst (catalyst support, Pt loading and initial particle size, test conditions, and testing protocols) differ from article to article and have made a summative understanding of the fundamental degradation mechanisms very difficult. Thus a cohesive effort is still needed to bring a global understanding of the degradation mechanisms so as to develop efficient mitigation strategies.…”

mentioning

confidence: 99%

“…1,[11][12][13] Three mechanisms of cathode catalyst degradation are usually considered as the origin of performance decay: (i) catalyst dissolution with or without redeposition (i.e., Ostwald ripening in the former case), (ii) catalyst nanoparticle coagulation (coalescence) via crystal migration and (iii) catalyst detachment due to carbon corrosion. 12,14,15 However, the participation of multiple factors influencing the stability of the cathode catalyst (catalyst support, Pt loading and initial particle size, test conditions, and testing protocols) differ from article to article and have made a summative understanding of the fundamental degradation mechanisms very difficult. Thus a cohesive effort is still needed to bring a global understanding of the degradation mechanisms so as to develop efficient mitigation strategies.…”

mentioning

confidence: 99%

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Platinum Dissolution in Fuel Cell Electrodes: Enhanced Degradation from Surface Area Assessment in Automotive Accelerated Stress Tests

Rice

Urchaga

Pistono

et al. 2015

J. Electrochem. Soc.

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Automotive fuel cells are plagued by high platinum-based cathode catalyst costs exacerbated by high catalyst loadings to circumvent performance losses induced by typical urban drive cycles. Accelerated durability tests are commonly used to evaluate the impact of nano-structure and/or operating conditions on cathode catalyst loss rates. To map out loss rates the electrochemical surface area (ECSA) of the catalyst is periodically monitored. Herein the accelerated stress testing was performed 25,000 times by imposing perturbations from 0.9 V to 0.6 V in a triangular wave profile while the ECSA was measured by assessing the hydrogen adsorption/desorption region with a lower potential limit of 0.025 V at intermittent points during the triangular wave perturbations. The ECSA loss observed during the 25,000 triangle wave cycles is 7% when measured only 2 times, but 26.3% when measured 250 times. The exacerbated losses during frequent low potential ECSA measurements suggest a restructuring of the catalyst surface due to the formation of a protective β-oxide, as seen by alterations in the cyclic voltammtric profile and particle size distribution. The increasing price of fossil fuel stimulated by an impending near future accessible supply depletion combined with the increased awareness of the adverse contributions of the Internal Combustion Engines (ICEs) on global warming has driven an international research thrust toward alternative energy production for personal automotive transportation from alternative energy technologies. Proton Exchange Membrane Fuel Cells (PEMFCs) currently appear as one of the potential alternatives to ICEs for automotive applications due to their higher efficiency and the fact that they use hydrogen and air (21% oxygen) as fuel and oxidant, respectively, with water as the only by-product. Furthermore, depending on the production method, hydrogen can be considered as a renewable source of energy if generated in ways such as electrolysis from either wind turbines or solar energy.The commercialization and massive production of automotive PEMFC technologies is still a challenge due to durability and cost limitations.1 The PEMFC type is the most suitable fuel cell technology to replace ICEs for vehicle propulsion because of the solid electrolyte permitting comparable travel distances, available power for frequent fast idle-to-peak transients to support typically sized personal vehicles and fast startup/shutdown. However, the relatively low working temperature of PEMFCs (typically below 100• C, due to membrane limitations) requires the use of Pt based catalysts for both the anode and the cathode catalyst layers thereby significantly increasing their price. Utilization of finely dispersed catalyst nanoparticles onto a high surface electrically conducting substrates (typically high surface carbon supports) and optimization of catalytic layers have yet allowed a drastic decrease of the catalytic layer cost by lowering the Pt loading by a factor of 10 (reaching 0.4 mg. cm −2 total loading) in the past 30 ...

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Section: F1176mentioning

confidence: 99%

Section: F1176mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Platinum Dissolution in Fuel Cell Electrodes: Enhanced Degradation from Surface Area Assessment in Automotive Accelerated Stress Tests

Rice

Urchaga

Pistono

et al. 2015

J. Electrochem. Soc.

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“…The first is that the interim electrochemical measurements carried out during the durability evaluation could have affected the Pt dissolution, because the ORR performance in the outlet region decreased during the durability evaluation, and the load (current density) in the inlet region would have increased in order to compensate. 17 The second is that the ORR in the inlet region (shown in Fig. 2) carried out during the durability evaluation could have accelerated the Pt dissolution and re-deposition during the potential cycling.…”

Section: After As Durability Evaluation Inlet Nm (μM)mentioning

confidence: 99%

Durability of Pt Catalysts Supported on Graphitized Carbon-Black during Gas-Exchange Start-Up Operation Similar to That Used for Fuel Cell Vehicles

Yamashita

Itami²,

Takano³

et al. 2016

J. Electrochem. Soc.

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We investigated the durability of cathode catalysts during a start-up (SU) process similar to that used in actual polymer electrolyte fuel cell vehicle operation. The durability of Pt supported on graphitized carbon black (Pt/GCB) catalysts was evaluated in the practical SU process, i.e., the anode gas was successively cycled between air, hydrogen, and nitrogen. The effect of the SU process on the cell performance was evaluated using two types of catalysts (commercial Pt/GCB, and that prepared in house by the "nanocapsulemethod," n-Pt/GCB). The polarization curves and cyclic voltammetry were evaluated before and after the SU evaluation. The degradation of Pt nanoparticles and carbon supports was analyzed by transmission electron microscopy, scanning transmission electron microscopy, and micro-Raman spectroscopy. We also applied glancing incidence X-ray diffraction in order to observe the depth profiles of the Pt crystallite sizes in various interfacial regions. From these analyses, we found that the degradation of the Pt catalyst occurred not only in the gas outlet region but also the gas inlet region of the cathode. The degradation in the inlet region is ascribed to both the interim electrochemical evaluations and the potential fluctuations, which cause a dissolution of Pt nanoparticles used during the SU process. Polymer electrolyte fuel cells (PEFCs) are able to convert chemical energy directly to electrical energy with high efficiency and have shown promise to be an eco-friendly power source for residential cogeneration systems and fuel cell vehicles (FCV).1-3 Nevertheless, the widespread commercialization of PEFCs has been impeded because of the large amount of the platinum catalyst required, which must be minimized to reduce the system cost. 4 The minimization can be achieved, for example, by the improvement of utilization of Pt nanoparticles dispersed on carbon black supports (Pt/CB) with high surface area used as the cathode catalyst for PEFCs as well as the improvement of the durability. During the start-up and shutdown (SU/SD) cycles of the PEFCs, air and H 2 coexist transiently in the anode until the replacement of the former with the latter (or vice versa) is completed. Reiser et al. showed that this situation causes the cathode potential to climb to more than 1.5 V due to the so-called "reverse current mechanism", 5 which significantly accelerates the degradation of the catalyst due to the oxidation of the CB and the agglomeration or dissolution of the Pt nanoparticles. 6 In our previous research, we have developed a graphitized carbon black (GCB) supported Pt catalyst prepared by the "nanocapsule method" (n-Pt/GCB) to improve the performance of Pt catalysts. 7-9The high dispersion of the Pt nanoparticle catalyst particles on the GCB support prepared by this method provides enhanced oxygen reduction reaction (ORR) activity. It was also found that the durability of the n-Pt/GCB catalyst was improved during a potential cycling evaluation that simulated the variation of the cathode potential during the...

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Power Density and Durability in Fuel Cell Vehicles

Heidary¹,

Moein‐Jahromi²

2023

Hydrogen Electrical Vehicles

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Deleterious effects of interim cyclic voltammetry on Pt/carbon black catalyst degradation during start-up/shutdown cycling evaluation

Cited by 85 publications

References 41 publications

Platinum Dissolution in Fuel Cell Electrodes: Enhanced Degradation from Surface Area Assessment in Automotive Accelerated Stress Tests

Platinum Dissolution in Fuel Cell Electrodes: Enhanced Degradation from Surface Area Assessment in Automotive Accelerated Stress Tests

Durability of Pt Catalysts Supported on Graphitized Carbon-Black during Gas-Exchange Start-Up Operation Similar to That Used for Fuel Cell Vehicles

Power Density and Durability in Fuel Cell Vehicles

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