72 research outputs found
Polybenzimidazole (PBI) Functionalized Nanographene as Highly Stable Catalyst Support for Polymer Electrolyte Membrane Fuel Cells (PEMFCs)
No full textNanoscale graphenes were used as cathode catalyst supports in proton exchange membrane fuel cells (PEMFCs). Surface-initiated polymerization that covalently bonds polybenzimidazole (PBI) polymer on the surface of graphene supports enables the uniform distribution of the Pt nanoparticles, as well as allows the sealing of the unterminated carbon bonds usually present on the edge of graphene from the chemical reduction of graphene oxide. The nanographene effectively shortens the length of channels and pores for O2 diffusion/water dissipation and significantly increases the primary pore volume. Further addition of p-phenyl sulfonic functional graphitic carbon particles as spacers, increases the specific volume of the secondary pores and greatly improves O2 mass transport within the catalyst layers. The developed composite cathode catalyst of Pt/PBI-nanographene (50 wt%) + SO3H-graphitic carbon black demonstrates a higher beginning of life (BOL) PEMFC performance as compared to both Pt/PBI-nanographene (50 wt%) and Pt/PBI-graphene (50 wt%) + SO3H-graphitic carbon black (GCB). Accelerated stress tests show excellent support durability compared to that of traditional Pt/Vulcan XC72 catalysts, when subjected to 10,000 cycles from 1.0 V to 1.5 V. This study suggests the promise of using PBI-nanographene + SO3H-GCB hybrid supports in fuel cells to achieve the 2020 DOE targets for transportation applications.This article is published as Xin, Le, Fan Yang, Yang Qiu, Aytekin Uzunoglu, Tommy Rockward, Rodney L. Borup, Lia A. Stanciu, Wenzhen Li, and Jian Xie. "Polybenzimidazole (PBI) functionalized nanographene as highly stable catalyst support for polymer electrolyte membrane fuel cells (PEMFCs)." Journal of The Electrochemical Society 163, no. 10 (2016): F1228. DOI: 10.1149/2.0921610jes. Posted with permission.</p
PEM Fuel Cell Degradation
No full textThe durability of PEM fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. While significant progress has been made in understanding degradation mechanisms and improving materials, further improvements in durability are required to meet commercialization targets. Catalyst and electrode durability remains a primary degradation mode, with much work reported on understanding how the catalyst and electrode structure degrades. Accelerated Stress Tests (ASTs) are used to rapidly evaluate component degradation, however the results are sometimes easy, and other times difficult to correlate. Tests that were developed to accelerate degradation of single components are shown to also affect other component's degradation modes. Non-ideal examples of this include ASTs examining catalyst degradation performances losses due to catalyst degradation do not always well correlate with catalyst surface area and also lead to losses in mass transport.</jats:p
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Durability Study of Membrane Electrode Assembly for Heavy-Duty Fuel Cells
No full textPolymer electrolyte membrane fuel cells (PEMFCs) are a zero emission replacement for heavy duty applications due to their range, energy density and fast refueling times.[1] In 2020, the U.S. Department of Energy (DOE) lunched the Million Mile Fuel Cell Truck (M2FCT) consortium to fund fuel cell R&D to meet heavy duty truck standards.[2] Durability studies focusing on heavy-duty applications for advanced materials testing under the M2FCT consortium have been extensively explored and continue to be analyzed to standardize the evaluation of next generation fuel cell materials.
This study combines in situ electrochemical characterization with ex situ analysis of single cell PEMFCs membrane electrode assemblies (MEAs) to predict long-term durability for heavy-duty applications. Various accelerated stress test (AST) parameters were analyzed to determine the stressors affecting the long-term durability. Local degradation resulting from repeated high voltage to low current cycles was analyzed by testing state-of-the-art materials. High potential holds at various conditions were analyzed to determine membrane chemical degradation. Repeated wet and dry cycles were performed to test the membrane mechanical durability. In situ electrochemical analysis include mass activity, electrochemical surface area, hydrogen crossover, and polarization curves were collected and compared among the MEAs. Ex situ analysis includes quantification of membrane thinning at end of life and fluoride emission rate measurement for water effluent throughout the test was conducted to study the membrane degradation.
Acknowledgement:
This work was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy (EERE), US DOE through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.
References:
David A. Cullen, K. C. Neyerlin, Rajesh K. Ahluwalia, Rangachary Mukundan, Karren L. More, Rodney L. Borup, Adam Z. Weber, Deborah J. Myers, and Ahmet Kusoglu, New roads and challenges for fuel cells in heavy-duty transportation. Nat. Energy, 2021. 6(5): 462-474.
DOE Launches Two Consortia to Advance Fuel Cell Truck and Electrolyzer R&D. 2020; Available from: https://www.energy.gov/eere/articles/doe-launches-two-consortia-advance-fuel-cell-truck-and-electrolyzer-rd
Author Correction: Grooved electrodes for high-power-density fuel cells
No full textCorrection to: Nature Energy. Published online 25 May 2023. This paper was originally published under a standard Springer Nature license (© The Author(s), under exclusive licence to Springer Nature Limited). It is now available as an open-access paper under a Creative Commons Attribution 4.0 International license, © The Author(s). The error has been corrected in the online version of the article
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Accelerated Stress Testing (AST) Protocol Development for Heavy-Duty Fuel Cells
No full textAbstract:
Polymer electrolyte membrane fuel cells (PEMFCs) are promising for heavy duty applications due to their unique scalability in terms of both power and energy [1], and the U.S. Department of Energy (DOE) established the Million Mile Fuel Cell Truck (M2FCT) consortium in 2020 to advance fuel cell truck R&D[2, 3]. The 2025 end-of-life (EOL) target of M2FCT is to achieve 2.5 kW/gPGM at 0.7 V after 25, 000 hour-equivalent accelerated durability test. Several novel materials have been developed and integrated into membrane electrode assemblies (MEA) and catalysts that meet the EOL target after 90,000 potential cycles in H2/N2 have been reported. However, these reports do not imply that the M2FCT 2025 target has been met since development of the durability protocol and lifetime prediction models for heavy-duty fuel cells are ongoing efforts. The tentative heavy-duty MEA accelerated stress test (AST) protocol consists of H2/Air potential cycling under elevated temperature (90 °C) [4], which the consortium is still actively refining based on the feedback received from the AST Working Group (ASTWG).
In this talk, we will systematically summarize the results from the 500-hour H2/Air testing MEA AST, together with various characterization results from microscopy and X-ray analysis, as well as nondispersive infrared to measure support carbon corrosion and fluoride emission rates to measure membrane degradation. With better understanding of the degradation for each component under different testing conditions, we will illustrate the effect of RH (30%, 50%, 90%, and 100%) on the degradation rates of the membrane and catalyst and explain the rationale behind the proposed MEA AST protocol. The degradation rates from the MEA AST protocol were fit into lifetime prediction models and acceleration factors were calculated based on different RHs and cathode catalyst loadings. Refinement of the protocol based on feedback received will also be briefly introduced.
Acknowledgment:
We acknowledge the financial support for this work from the U.S. DOE) Hydrogen and Fuel Cell Technologies Office (HFTO) through the M2FCT consortium, technology managers Greg Kleen and Dimitrios Papageoropoulos.
References:
David A. Cullen, K. C. Neyerlin, Rajesh K. Ahluwalia, Rangachary Mukundan, Karren L. More, Rodney L. Borup, Adam Z. Weber, Deborah J. Myers, and Ahmet Kusoglu, New roads and challenges for fuel cells in heavy-duty transportation. Nat. Energy, 2021. 6(5): 462-474.
Million Mile Fuel Cell Truck (M2FCT) Consortium Launched. 2020; Available from: https://millionmilefuelcelltruck.org/news.
DOE Launches Two Consortia to Advance Fuel Cell Truck and Electrolyzer R&D. 2020; Available from: https://www.energy.gov/eere/articles/doe-launches-two-consortia-advance-fuel-cell-truck-and-electrolyzer-rd.
Accelerated Stress Testing (AST) Protocols for Heavy-Duty Fuel Cells. 2024; Available from: https://millionmilefuelcelltruck.org/ast-protocols
Heat and Water Transport in a Polymer Electrolyte Fuel Cell Electrode
No full textIn the present scenario of a global initiative toward a sustainable energy future, the polymer electrolyte fuel cell (PEFC) has emerged as one of the most promising alternative energy conversion devices for various applications. Despite tremendous progress in recent years, a pivotal performance limitation in the PEFC comes from liquid water transport and the resulting flooding phenomena. Liquid water blocks the open pore space in the electrode and the fibrous diffusion layer leading to hindered oxygen transport. The electrode is also the only component in the entire PEFC sandwich which produces waste heat from the electrochemical reaction. The cathode electrode, being the host to several competing transport mechanisms, plays a crucial role in the overall PEFC performance limitation. In this work, an electrode model is presented in order to elucidate the coupled heat and water transport mechanisms. Two scenarios are specifically considered: (1) conventional, Nafion® impregnated, three-phase electrode with the hydrated polymeric membrane phase as the conveyer of protons where local electro-neutrality prevails; and (2) ultra-thin, two-phase, nano-structured electrode without the presence of ionomeric phase where charge accumulation due to electro-statics in the vicinity of the membrane-CL interface becomes important. The electrode model includes a physical description of heat and water balance along with electrochemical performance analysis in order to study the influence of electro-statics/electro-migration and phase change on the PEFC electrode performance.</jats:p
Modeling of Durability Effect on the Flooding Behavior in the PEFC Gas Diffusion Layer
No full textThe gas diffusion layer (GDL) plays a critical role in the overall performance of a polymer electrolyte fuel cell (PEFC), especially in the mass transport control regime due to suboptimal liquid water transport. Liquid water blocks the porous pathways in the catalyst layer and gas diffusion layer thereby causing hindered oxygen transport from the channel to the active reaction sites. This phenomenon is known as “flooding” and is perceived as the primary mechanism leading to the limiting current behavior in the cell performance. The pore morphology and wetting characteristics of the cathode GDL are of paramount importance in the effective PEFC water management. Typical beginning-of-life GDLs exhibit hydrophobic characteristics, which facilities liquid water transport and hence reduces flooding. Experimental data, however, suggest that the GDL loses hydrophobicity over prolonged PEFC operation and becomes prone to enhanced flooding. In this work, we present a pore-scale modeling framework to study the structure-wettability-durability interplay in the context of flooding behavior in the PEFC GDL.</jats:p
IHTC14-22703 HEAT AND WATER TRANSPORT IN A POLYMER ELECTROLYTE FUEL CELL ELECTRODE
No full textABSTRACT In the present scenario of a global initiative toward a sustainable energy future, the polymer electrolyte fuel cell (PEFC) has emerged as one of the most promising alternative energy conversion devices for various applications. Despite tremendous progress in recent years, a pivotal performance limitation in the PEFC comes from liquid water transport and the resulting flooding phenomena. Liquid water blocks the open pore space in the electrode and the fibrous diffusion layer leading to hindered oxygen transport. The electrode is also the only component in the entire PEFC sandwich which produces waste heat from the electrochemical reaction. The cathode electrode, being the host to several competing transport mechanisms, plays a crucial role in the overall PEFC performance limitation. In this work, an electrode model is presented in order to elucidate the coupled heat and water transport mechanisms. Two scenarios are specifically considered: (1) conventional, Nafion ® impregnated, three-phase electrode with the hydrated polymeric membrane phase as the conveyer of protons where local electro-neutrality prevails; and (2) ultra-thin, two-phase, nano-structured electrode without the presence of ionomeric phase where charge accumulation due to electro-statics in the vicinity of the membrane-CL interface becomes important. The electrode model includes a physical description of heat and water balance along with electrochemical performance analysis in order to study the influence of electro-statics/electro-migration and phase change on the PEFC electrode performance
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