Akshaya Jena and Krishna Gupta Porous Materials, Inc. NY, USA Fuel Cells R&D Enhancing Performance through Pore Structure

Dependence of Performance of Fuel Cells on Pore Structure of its Components Many fuel cell porous components  Examples: Membranes, GDLs, Separators, Electrodes Pore structure governs fluid flow Pore structure influences kinetics of physico- chemical processes occurring in fuel cells Pore structure characteristics are critical factors that determine performance of fuel cells

Dependence of Performance of Fuel Cells on Pore Structure of its Components Important and relevant pore structure characteristics, which need to be determined:  Pore diameter  Pore throat diameter  Pore volume  Pore distribution  Graded pore structure  Surface area  External surface area  Total porosity  Hydrophobic and hydrophilic nature of pores in a mixture  Liquid and gas permeability  Diffusional flow

Influence of working environment on pore structure needs to be determined  Chemical environment  Operating temperature  Humidity  Stress generated during operation Dependence of Performance of Fuel Cells on Pore Structure of its Components

Many techniques are available for evaluation of pore structure characteristics of fuel cell components: Capillary Flow Porometry  Measures:  Wide range of through pore throat diameters  Pore distribution  Gas permeability  Structure over a range of: Temperature  Stress Chemical environment  Controlled humidity Techniques for Measurement of Pore Structure Characteristics

Liquid Extrusion Porosimetry  Measures:  Through pore volume  Through pore diameters  Pore distribution  Hydrophobic pores  Hydrophilic pores  Structure over a range of: Temperature  Stress Chemical environment  Controlled humidity

Capillary Condensation Flow Porometry  Measures:  Through nanopore diameter  Distribution  Flow rate  Without structural distortion (Negligible pressure, Ambient temperature) Permeametry  Measures:  Gas, vapor, and liquid transmission rates  Many chemical species  Over a wide range of temperature, pressure, and concentration Techniques for Measurement of Pore Structure Characteristics

Vacuapore  Measures:  Through and blind hydrophobic pore volume  Pore diameter  Pore distribution Mercury Intrusion Porosimetry  Measures:  Through and blind pore volume  Pore diameter  Pore distribution Techniques for Measurement of Pore Structure Characteristics

BET Sorptometry  Measures:  Surface area  Very small through and blind pore volume  Distribution  Chemisorptions of many chemicals over a wide range of temperature and pressure Pycnometry  Measures:  True and bulk density Techniques for Measurement of Pore Structure Characteristics

About PMIPMI  Porous Materials, Inc. designs, manufactures, and sells instruments for pore structure characterization  Has vast experience in patenting of novel technology for pore structure characterization and developing custom instruments for a wide variety of applications  Has published many papers and presented many oral and poster papers in conferences on pore structure, characterization of fuel cells, and battery components  Has supplied instruments to many fuel cell and battery related industries and research laboratories all over the globe How Can PMI Help?

Pore Structure Characterization Instruments by PMI PMI Fuel Cell Porometer and Advanced Capillary Flow Porometer Specially designed for fuel cell components

Other unique instruments Liquid Extrusion Porosimeter and Vacuapore Pore Structure Characterization Instruments by PMI Click here to download a full PDF on this subject.

Pore Structure Characterization Instruments by PMI The Capillary Condensation Flow Porometer Specifically designed for membranes with fine pores.Capillary Condensation Flow Porometer

Pore Structure Characterization Instruments by PMI All the instruments needed for pore structure characterization of fuel cell components are manufactured by PMI.PMI

Fully automated:  Test execution  Data acquisition  Data storage  Data reduction Windows-based menu driven simple operation Objective, accurate, and reproducible results The Fully Automated Instruments

PMI In-House Contract Testing Laboratory  We test fuel cell components of many customers from all over the globe.  Test time can be as low as two days.

What is Toray Paper?  A carbon coated material extensively used in the fuel cell industry Volume of Different Kinds of Pores  Different functions of fuel cell components are governed by different kinds of pores  PMI instruments used to measure pore volumes  Volume of the through pores: PMI Liquid Extrusion PorosimeterPMI Liquid Extrusion Porosimeter  Volume of through and blind pores: PMI Mercury Intrusion PorosimeterPMI Mercury Intrusion Porosimeter  Volume of through and blind hydrophobic pores: PMI VacuaporePMI Vacuapore Example of Application of PMI Instruments: Pore Structure Characterization of Toray Paper

Measured Pore Volume Through Pores: 75% of the pore volume Blind Pores: 25% of the pore volume Hydrophobic Pores: 29% of pore volume Hydrophilic Pores: 71% of pore volume Click here to download a full PDF on this subject.

Pore volume distribution given as distribution function Differences between peaks used to estimate distribution of blind pores and hydrophilic pores Pore Volume Distribution of Different Kinds of Pores

Median pore diameters of various kinds of pores are shown in the table on the following slide. Click here to download a PDF on the subject.

CharacteristicsThrough Pores Blind PoresHydrophobic Pores Hydrophilic Pores % of Pore Volume 75%25%29%71% Median Pore Diameter 60  m40  m35  m50  m Kind of PoreHydrophilicHydrophobicBlind PoresThrough Pores Median Pore Diameters of Various Pores  Through pores primarily hydrophilic  Blind pores primarily hydrophobic  Hydrophilic through pores also measurable by PMI Water Extrusion PorosimeterPMI Water Extrusion Porosimeter

Pore throat diameters determine  Flow rate of fluid through the through pores  Restrictions for passage of large particles through the through pores  Through pore throat diameters measurable by: PMI Capillary Flow PorometerPMI Capillary Flow Porometer Characteristics of Through Pores Responsible for Fluid Flow

CharacteristicsValues The Largest Throat Diameter  m Mean Flow Throat Diameter  m Range of Throat Diameters 20 – 45  m Change of Pore Diameter Along Pore Length Small Median Pore Diameter based on Volume 60  m Volume of Pores75% Nature of PoresHydrophilic Pore Throat Characteristics of Through Pores

Distribution of Pore Throat Diameters Most of the through pore throat diameters are in the range of  m

Comparison of Pore Throat Diameters and Volume Based Pore Diameters  Comparison with volume based values suggests that shapes of through pores are not like hour glasses  Through pore diameters do not change appreciably along the pore length and are similar in magnitude Click here to download a PDF on the subject.

 You can visit our website to see the wide spectrum of pore structure capability that our instruments offerwebsite  If you have a special need that is not part of PMI’s standard test list, the engineers at PMI will be happy to talk to you about your testing requirements and come up with a suitable solution. Special Needs

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