Atanassova, Paolina

Brewster, James

Kyrlidis, Angelos

Moeser, Geoffrey

Rice, Gordon

Sun, Yipeng

Xie, Jian

UNT Digital Library

Low Precious Metal Alloy Catalysts and Durable Carbon SupportsP. Atanassova, Y. Sun, G. Rice, J. Brewster, J. Xie, A. Kyrlidis, G. MoeserCabot Fuel Cells, Albuquerque, NM2006 Fuel Cell Seminar, November 13-17, 2006, Honolulu, HawaiiSession # 3B, Low Temperature Fuel Cells IICabot Fuel Cells• New name, clear commitment to Fuel Cells commercialization • Combining the expertise in carbon supports with electrocatalyst manufacturing • New methods, new results! • Hydrogen-air FC & DMFC materials solutions• Advanced electrocatalysts for Hydrogen Air Fuel Cells:• Low precious metal alloys• Oxidation resistant carbon supports• Modified carbon black supports for low humidity operationCabot Fuel Cell Materials Development • Low Precious Metal Alloy Electrocatalysts• Advanced Carbon Supports• Easy Handling for Inks Formulation• Optimized Electrode Layers and MEA StructuresCostgPt/kW;  $/kWPerformancemW/cm2Durability5000 hHigh Throughput Catalyst Discovery Platform is Key Element for Rapid Optimization of Complex Alloy CompositionsElectrochemical and Physical CharacterizationHigh Throughput Synthesis Rapid Cathode Layer FabricationRapid Screening in MEA ConfigurationHigh Volume Production1 PtCoCu2 PtCoFe3 PtFeCu4 PtNiCu5 PtNiFe6 PtPdCu7 PtPdCo8 PtPdFe9 PtMnFe10 PtPdMn11 PtNiCo12 PtCoAg13 PtFeAg14 PtNiAg15 PtPdNiCoTest Conditions:• Non IR corrected, 50 cm2 MEA, NafionTM 112• Loadings: Cathode: 0.2 mgM/cm2, Anode: 0.05 mgPt/cm2• 80ºC, 1.5 H2/2.5 air at 1A/cm2, 100% RH, 30 psig, 10min/point 0.400.500.600.700.800.901.000 1 2 3 4 5 6 7 8 9 10A/mg Pt cathodeCell Voltage (V)20% PtCoCu/C20% PtNiCo/C20% PtCo/C20% PtNiFe/C20% Pt/C20% PtNi/CBest Pt alloy compositions show up to 2 fold mass activity improvement in hydrogen air fuel cellTwo Fold Mass Activity Improvement Demonstrated byTernary Pt- Alloy Supported CatalystsSuperior MEA Performance at Low Precious Metal LoadingsHighly Dispersed Alloy Catalysts0.20.30.40.50.60.70.80.91.00.0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.8 0.9 1.0Current Density (A/m2)Cell Voltage (V)MEA loadings: 0.15 mg Pt/cm2 total loadingCathode: 0.1 mg Pt/cm2; Anode: 0.05 mg Pt/cm20.8 V, 0.6 g Pt/kW 0.75 V, 0.4 g Pt/kW 0.7 V, 0.3 g Pt/kW Test Conditions:• 50 cm2, NafionTM 112 • 80°C, 1.5 H2/2.5 air at 1A/cm2, 100% RH, 30 psig                 10 min/point, Non IR correctedPt (111): 40.36 (2θ); a: 3.87 ÅParticle size (XRD): 2.4 nmHigh Absolute Performance Combined with Low Precious Metal LoadingsTest Conditions:• Non IR corrected 50 cm2, NafionTM 112, cathode: as listed; anode: 0.05 mgPt/cm2,• 80°C, 1.5 H2/2.5 air at 1A/cm2, 100% RH, 30 psig, 10 min/pointCurrent Density (A/cm2)Cell Voltage (V)0.00.10.20.30.40.50.60.70.80.91.00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0A: 0.3 mgPt/cm2, Pt alloy/KBB: 0.5 mgPt/cm2, 50 wt.% Pt/KB2006• High Metal Loading Catalyst on High Surface Area Carbon Support• Identical performance at approximately half of the Pt content• At 0.8 V a power density of 0.32 W/cm2 was achieved• At 0.7 V approximately 0.56 W/cm2 (total PM loading, anode plus cathode of 0.35mgPt/cm2), which corresponds to approximately 0.6 gPt/kW.• The corresponding value for Pt only catalyst at 0.7 V is approximately 0.9 gPt/kWShort Stack Testing Validates Alloy Catalysts PerformanceStack Test Conditions:• 5 cell, large area, NafionTM 112 cathode: as listed; anode: 0.05 mgPt/cm2• 80/80/80oC, 55/55 kPa, 1.5/2.5 stoich • 80/80/80oC, 190/190 kPa, 1.5/2.5 stoich• 80/80/64oC, 175/175 kPa, 2/2.5 stoich• Short stack evaluation completed by Hydrogenics Corporation • 0.6 gPt/kW demonstrated in a short stack at 0.7 V and stoich test conditionsCurrent Density (A/cm2)00.10.20.30.40.50.60.70.80.910 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Average Cell VoltagePt/KB, 0.5 mg Pt/cm2Pt Alloy/V, 0.25 mg Pt/cm250% Pt/KB Pt Alloy/V0.8V 0.67 0.95 420.75V 1.04 1.7 630.7V 1.37 2.75 100Mass activity (A/mg Pt cathode) Performance improvement (%)1.580.940.6200.20.40.60.811.21.41.61.80.8 0.75 0.7Cell Voltage (V)Stack performance (g Pt/KW)80/80/80 oC, 190/190 kPa, 1.5/2.5 stoichLong-Term Durability Under Cycling ProtocolsNormolized Specifc Surface Area vs. CV Cycle0%20%40%60%80%100%120%initial 15 K cycles 30 K cyclesSpecific Surface Area  [%of initial]Pt/C Pt alloy/C01020304050607080901001000 10000 100000Number of CyclesNormalized Pt ECSA (%)Voltage loss (mV)50 mA/cm2 6400 mA/cm2 13Test Conditions: 50 cm2 MEA, cycling under H2/air at 80°C and 100% RH between 0.7 and 0.9 V IR-free voltage (30 s hold at each potential) combined with periodical evaluation of the Pt surface area using cyclic voltammetry and performance.Pt alloy catalyst shows 30% loss of surface area after 20 K cycles and no further loss is observed until 30K cycles !Long Term Performance Losses Related to Carbon Corrosion• Carbon Support Durability is considered to be a major barrier for commercialization of automotive fuel cells• Carbon corrosion is accelerated during start/ stop cycles and at high temperature operating conditions•Type of performance losses related to carbon corrosion• Pt sintering due to loss of active phase/support interaction• Oxidation of carbon surface leads to layer flooding effects• Break down in carbon/carbon interface• Conventional approaches to improving carbon durability lead to trade offs between durability, absolute performance and catalyst ink propertiesAbility to Control Carbon Support PropertiesParticle SizeStructureSurface ChemistryCombination of morphology controland surface modification allows for rational design of carbon materials • Carbon black morphology can be controlled to design the length scale of gas and water transport channels• Various degrees of carbon support graphitization can be achieved• Carbon support surface chemistry can be modified+ N YN+Carbon Black Diazonium SaltModified Carbon BlackCarbon Corrosion Analysis Approach• Investigate and evaluate the corrosive behavior of dispersed carbon blacks in low temperature fuel cell environment• Corrosion resistance evaluation protocol adopted from GM/DOE– Polarization curves test conditions 80°C,stoich flows A/C = 3/3, 50% RH, 7 psig• Study the effect of platinum loading, surface modification and morphology of the carbon blacks on the corrosive behavior of electrocatalysts.• Goal – less than 30 mV loss at 1 A/cm2after 100 hrs corrosion testStart-up CellConditioning(12 to 16 hours)Measure Polarization CurvesApply 1.2V - 100% RH H2/N2 for 15 hoursMeasure Polarization CurvesApply 1.2V - 100% RH H2/N2 for 5 -15 hourst <100 hours?NoYesShutdown CellSevere Corrosion Losses with Standard Supports60% Pt / Ketjen Black• > 100mv loss at 1A/cm2 only after 15hrs• > 53% Loss in EC area after 45hrs of standard corrosion protocol0.20.30.40.50.60.70.80.91.00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5Current Density (A/cm2)Voltage (V)0hr15hr20hr25hr30hr35hr40hr45hrPolarization curves test conditions: 80/80/80°C, stoichflows A/C = 3/3, 50% RH, 7 psigSurface Modification Effectively Enhances Carbon Corrosion Resistance• >100mV Loss at 1A/cm2 after 50hrs• Improvement is related to the coverage of functional groups on carbon surface • Functional groups stabilize the carbon surface0.20.30.40.50.60.70.80.90.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4Current Density (A/cm2)Voltage (V)0hr15hr20hr25hr30hr35hr40hr45hr50hrPolarization curves test conditions: 80°C, stoich flows A/C = 3/3, 50% RH, 7 psig60% Pt / Modified Carbon Black  (MCB)Surface Modification Enables Operation at Low Relative Humidity Conditions0.200.300.400.500.600.700.800.901.000.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00Current Density (A/cm2)Voltage (V)100 % relativehumidity50% relativehumidity• 100 % relative humidity test: flow stoich  = 2.0 (A/C), cell temperature 80°C back pressure =10 psig ( A/C), RH=100% (A/C)• 50 % relative humidity test: flow stoich  = 2.0 (A/C), cell temperature 80°C back pressure =10 psig ( A/C), RH=50%/50% (A/C)Superior Corrosion Resistance with New Cabot Carbon Support• Identical initial absolute performance after layer optimization• No loss of performance after 105 hrs corrosion test0.200.250.300.350.400.450.500.550.600.650.700.750.800.850.900.951.000.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Current Density (A/cm2)Voltage (V)New Cabot Carbon 7psig 0hrNew Cabot Carbon 30 psigStandard Carbon 30 psigStandard carbon 7 psig 0hrNew Cabot Carbon  7 psig 105hrStandard Polarization Curves Test Conditions: 80C, constant flow - 520/2040 mL/min A/C, 100% RH, 30 psigCorrosion Test Polarization Curves: 80C, stoich flow 3/3 A/C,50% RH, 7 psig60% Pt / Corrosion Resistant Carbon (CRC) Summary  Alloy Electrocatalysts: Two fold mass activity improvement by Pt-alloy catalysts High absolute performance combined with low precious metal  loadings in a single cell and short stack Significant durability improvement under cycling protocols  New Carbon Supports: Surface modification of carbon supports effectively enhances carbon corrosion resistance and enables operation at low relative humidity operating conditions  No performance loss after 105 hours of standard corrosion protocol without sacrificing initial performance Combination of durable Pt alloy catalysts with corrosion-resistant carbon supports is a viable way for next generation automotive fuel cell materialsFuture Work Cabot’s press release on November13th,2006 announced plans to introduce new products in Q1, 2007: Superior Durability Electrocatalysts based on Corrosion Resistant Carbon (CRC) supports Superior Performance Electrocatalysts for Operation at Low Relative Humidity based on Modified Carbon Blacks (MCB) For additional information: Visit us at Cabot’s boot #102 info@cabotfuelcells.com Presentations at ECS meeting, CancunAcknowledgements• Cabot Corporation • DOE Hydrogen Program, Award DE-FC0402AL67620• NIST ATP Program 70NANB4H3019• The whole Cabot team and especially: Greg Romney, Fred Von Gotteberg, Yakov Kutsovsky, Martin Green, Geoffrey Moeser, Yvette Herrera, Leonard Perez, Jason Zack• Madhusudhana Dowlapalli, Plamen Atanassov, Ceramic and Composite Materials Center, University of New MexicoCabot’s Facility in Albuquerque

Low Precious Metal Alloy Catalysts and Durable carbon Support

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Low Precious Metal Alloy Catalysts and Durable carbon Support

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