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2006 DOE Annual Review 1

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Tungsten Cathode Catalyst for PEM Cells

2006 DOE Hydrogen, Fuel Cells Infrastructure Technologies Program Review

Project ID# FCP 40This presentation does not contain any proprietary or confidential information

May 17, 2006

Joel Christian, Robert Mendenhall, Sean Smith, Richard Gingerich, Hans-Joachim Lunk, Tuan Dang

OSRAM SYLVANIA Products Inc.


2

Overview

TimelineProject Start: Feb. 1, 2005Project End: July 1, 2006Percent Complete: 90%

BudgetProject: $406,250- DOE Share: $325,000- Contractor: $81,250Funding in ‘05: $283,236

Technical Barriers/Targets

Non-Pt Catalyst Activity• > 130 A/cm³ @ 0.8V

Durability• 5000 hours (cycling)

Cost• < 8 $/kW

PartnersLANL — testing and ink formulation


3

Objectives

Perform R&D on tungsten electrocatalysts to improve power output per gram of material from baseline. This includes evaluating current catalyst in cathode application, and optimizing catalyst synthesis to achieve activity improvement towards attaining the DOE technical targets for non-platinum catalysts. Performance evaluation at 250 hours, and over 1000 hours.

The goal of this work is to produce a catalyst with high specific power at a cost significantly lower than platinum.


4

Approach

• Employ reduced polytungstates as cathode electrocatalysts

• Seek performance improvements by optimizing:– precursor composition– precursor loading on carbon– ink formulation– activation conditions

• Perform electrochemical tests for performance and lifetime


5

Technical Accomplishments

• Established catalysis in rotating disk half-cell• Demonstrated catalyst improvement

– At LANL• comparing 2004 and 2005 materials, W|Pt 5cm² cell• exceeded project milestone by 50% to 0.02 A/cm²

– at 0.24V, during 20 hr life test

– Internal testing• 4-fold improvement to 0.035 A/cm² at 0.24V• demonstrated catalyst life to 3200hrs


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Technical Accomplishments

• Completed work in 5 key tasks:– activation conditions – precursor composition– precursor loading on carbon– ink formulation– analysis

• Composition change provided the increase in cathode performance


Activated POM on XC-72

-0.000035

-0.00003

-0.000025

-0.00002

-0.000015

-0.00001

-0.000005

0

0.000005

0.00001

0.000015

-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Potential (V vs RHE)

Cel

l Cur

rent

(Am

ps)

O2 on day 1H2 on day 1Ar on day 1onset point

Oxygen

1 mV/sec

5 mV/sec

Hydrogen

Argon

Type IV - RDE "C" - 5mm GC disk

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Tungsten Only Cell — RDE (anode and cathode)

Demonstration of Catalytic Activity

Conditions:0.5 M HClO45 mV/sec2000 RPMCE: Carbon RodRE: SCE (Hg/Ag)WE: Thin film on

Glassy Carbon


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Tungsten Only Cell — RDE

XPS Analysis of RDE Surface

W(IV)

W(VI)

5700

5800

5900

6000

6100

6200

6300

6400

6500

6600

6700

6870727476788082848688

Binding Energy (eV)

N(E

)/E,s

mo1

1

XPS

XPS

Expected Pt Simulation

Pt

Pt

PtO

PtO

PtOads

PtOads

Pt

Pt

PtO2

PtO2

Pt location

XPS Signal

Possible Platinum Species

• platinum undetected• XPS shows reduced W(IV) present


9

Project Results – LANL Testing

Activity Improved to 0.078 A/cm²

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08i (cell current in amps/cm²)

V (v

olts

)OSI Type 1 LANL (2004)

OSI Type 2 LANL (2005)


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Project Results – LANL Testing

2004 2005

both tests at 0.24V, 5cm² cell2004 Test: ~0.04 A in cell = 0.008 A/cm²2005 Test: 0.1 A in cell = 0.02 A/cm²This comparison shows an improvement of 2.5x, project milestone was 2x

20 hour life test at 0.24V shows 2.5x improvement to 0.02 A/cm²

OSRAM-SYLVANIA Cathode Catalyst TestingShort Life Test

Anode: 0.20 mgPt/cm2; Cathode: 0.39 mgW/cm2

MEA Cell Area: 5 cm2; Membrane: Nafion 112; Tcell: 80°C; Pressure: 30 psigH2/Air Flow: 160/550 sccm

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 5 10 15 20Time / h

Cur

rent

@ 0

.24

V / A


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Cell Current (A/cm³)

Cel

l Pot

entia

l (V)

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Project Results – Current Output at 2000 hrs

60°C, H2:Air, without iR correction, test at OSRAM SYLVANIA

Type II Tungsten Catalysttest at OSRAM SYLVANIA

at 2000 hours

Volumetric current density at 0.8V exceeds DOE non-precious status

DOE status

Type II Tungsten Catalyst (LANL Decal method)

Type I Catalyst (LANL)

DOE 2010 target


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Project Results - Life

No Degradation in Cell Performance to 3200 Hours

H2:Air, initially RT then 60°C

0

2

4

6

8

10

12

14

0 500 1000 1500 2000 2500 3000 3500

Hours of operation (hr)

Pow

er (W

/cm

³)

0

5

10

15

20

25

30

35

40

Volu

met

ric C

ell C

urre

nt D

ensi

ty (A

/cm

³)

Poweri at 790mV avg


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Accomplishments – Activation Task

reduced POM

re-arrangement changes geometry

2.5 Å3.3 Å

+ 6 e-

Source: Jeannin, IC 1980 p 2933

W — W W — W

-7

-6

-5

-4

-3

-2

-1

0

1

2

-1.5 -1 -0.5 0 0.5 1

Potential (Volts vs SCE)

Cur

rent

(mA

)

50 mV/sec

Cyclic Voltammogram of Na6[H2W12O40] precursor Reduction Pathway for Metatungstate

Source: Launay, JINC 38, 807 (1976)


14

Precursor loading on carbon

Pore Size Distribution of XC-72

•Carbon Analysis:•PZC (isoelectric point)•pore size

•Objective:•optimizing of W loading on C

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POM has a higher possible site density (SD) than Pt

7.6 (1020sites/cm³)16 (1020sites/cm³)75% Metal Utilization 5% Metal Utilization

Idealized polytungstate and Pt electrode surfaces

Future Work

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Tungsten catalyst on track to meet the 2010 targets

Mat’l TOF SD SDMAX A/cm³Pt(2) 25 3.2

0.62

4.2

POMMAX 5 16 1300

3.1

7.6(1,4) 1300

W—POM(current)

1.59 16(4) 16

2010 POM 2 136

req’d3 1.6-4 60 - 160

ref 2: Gasteiger et al, Appl Cat B 56 (2005) 9-35

ref 1: Fuel Cell Handbook v2 p 471, citing Kinoshita

ref 4: lecture notes, Jim Benushi, Cabot Corp.

ref 3: Wagner et al, DOE Workshop 3/20/03

6.77x

SD = site density(1020 catalytic sites per cm³)

TOF = turnover frequency(catalytic reactions per second per site)

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Areas for Improvement

Charge Transfer Kinetics

Active Sites

Stability Enhancement

Redox Tuning

Compositional Changes

(TOF)

(SD)

(TOF, SD)

(TOF, SD)

(TOF, SD)


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Future Work• Project conclusion

– complete data collection– final report by 6/30/06

• Proposed for FY07– Continuing investigation on:

• demonstration of activity (in a Pt-free cell)• optimization of activation step• precursor composition• methods to improve loading/dispersion

• Proposed multi-year program FY07/FY10 – meet 2010 DOE target of 130 A/cm³


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Summary• Catalysis demonstrated on rotated disk electrode

– anode and cathode catalysis• PEM Cell performance demonstrated

– above DOE’s non-precious metal 2004 status– cathode operation to 3200 hours– project milestone exceeded

• Space model shows on-track to 2010 target– plan proposed to achieve 130 A/cm³


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Backup Slides


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Critical Assumptions and Issues• Adventitious Platinum

– Pt could migrate across membrane during• synthesis/activation• operation

– Protocol is needed to assess effect in PEM cell• detection of Pt in non-Pt catalyst area• quantification of Pt in non-Pt catalyst area• performance effect of Pt in non-Pt catalyst area

– Life test MEA assumes no Pt• analysis protocol being developed


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Acid Resistant Elements


Polyoxometalate (POM) - Features• Keggin type shown• One central heteroatom• Octahedra of WO6 “poly”atoms• Substituted “poly”atoms

– Poly- W, Mo, V, Nb, Ta– Hetero- 12 – 50 elements possible– Lacunary possible

• Can be extremely soluble• Potential “Designer” material

– Redox properties– High charge– High ionic weight– High charge delocalization

10 Å


AMT Properties• Isopolymetalate• Formula: (NH4)6[H2W12O40] • 5H2O• MW = 2958 g/mol (plus ~5 H2O)• Solubility: 2 kg/L • Charge localization: broad• Keggin structure with two H heteroatoms• pH of aqueous solution ~3 6-

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Acknowledgements:

U. S. Department of EnergyValri Lightner

Nancy Garland

Bob FillnowJeff Dann

Frank VenskytisTim Bard

Tom WolfePaul Sedor

Héctor AbruñaStan Whittingham

Piotr ZelenayTommy RockwardFrancisco Uribe

Mike Hickner

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