RECENT DEVELOPMENTS IN PGM-FREE &

ULTRALOW PT CATALYSTS AT ARGONNE

Di-Jia Liu

Chemical Sciences & Engineering DivisionArgonne National Laboratory, USA

Presented at 2017 Spring Annex 31/35 Meeting “HIGHLIGHTS OF INTERNATIONAL FUEL CELL RESEARCH 2017”, Graz, Austria, May 15-16, 2017

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Argonne National Laboratory – A Primer DOE Facility on

Energy, Environment & National Security Research

Founded in 1943, designated a National Laboratory in 1946 (nation’s first)

Multi-discipline, multi-program

– 3300 employees, 1600 Scientists/Engineers, 300 Postdocs

– $780 million annual budget

Broad-based R&D in basic science, energy resources, environmental management, and national security

Major user facilities

– Advanced Photon Source (APS)

– Argonne Tandem Linear Accelerator System (ATLAS)

– Center for Nanoscale Materials (CNM)

– Argonne Leadership Computing Facility (ALCF)

– Transportation Research & Analysis Computing Center (TRACC)

Located on 1500 wooded acres,25 miles southwest of Chicago’s Loop

Argonne National Laboratory – Major User Facilities

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Advanced Photon Source

Energy Science Building

Nano Material Research Center

Argonne Leadership Computing

Facility (ALCF)

US DOE FCTO Overview

MissionTo enable the widespread commercialization of hydrogen and fuel cell technologies through basic and applied research, technology development and demonstration, and diverse efforts to overcome institutional and market challenges.

Impact

2-4 million barrels/daypetroleum reduction by 2050

200- 450 million metric tons/year GHG emissions reduction by 2050

Strategy and Approach 2020 Targets

Fuel Cell Cost

Durability

H2 Cost at Pump

$40/kW

5,000 h 80,000 h

$1,000/kW*$1,500/kW**

<$4/gge

$10/kWhH2 Storage Cost (On-Board)

*For Natural Gas**For Biogas

U S DOE Fuel Cells & H2 Strategy

Reducing platinum usage to < 0.125 g/kW (or 10 g/vehicle at 80 kW rated power)

Increasing MEA durability to 5000 hours under cycling

Increasing stack power density to 0.85kW/L (or stack volume of 94L for 80kW unit)

Reducing costs of accessories, bipolar plates, air compressor, humidification, etc.

5

High

Medium

Low to Medium

Level of

Difficulty

BARRIERS NEAR TO MID-TERM LONG-TERM

700 bar tanks, composites, cryo-

compressedHydrogen Production and Delivery

Materials R&D for low pressure

storage

Non-PGM Catalysts

AEMs

Fuel Cell Cost and Durability

Hydrogen Storage

R&

D

Low-PGM catalysts , MEAs, performance

durability, components

H2 from NG/electrolysis; delivered H2, compression

H2 from renewables (PEC, biological, etc.),

pipelines, low P option

Near and mid-term research focuses

Replacing the platinum group metal (PGM) catalysts with earthly abundant materials

Improving ion conductivity and stability of alkaline electrolyte membranes

Long-term research focuses

• Strategic technical analysis guides focus areas

for R&D and priorities.

• Need to reduce cost to $30/kW and increase

durability from 2,500 to 5,000 hours.

• Advances in PEMFC materials and components

could benefit a range of applications

Strategies to Address Challenges

Catalyst Examples

●Lower PGM Content

●Pt Alloys

●Novel Support Structures

●PGM-free catalystsPEMFC Stack Cost Breakdown (FY13)

$0

$40

$80

$120

$160

2006 2008 2010 2012 2020

FC

Sys

tem

s C

os

t ($

/kW

net)

Projected Transportation Fuel Cell System Cost at 500,000 units/year

The Electrode Catalyst Challenges – Demand for Reducing

or Replacing Pt Usage

US DOE Technical Targets: Electrocatalysts for

Transportation Applications

7

a PGM content and loading targets may have to be lower to achieve system cost targets.

b Rated power operating point depends on MEA temperature and is defined as the voltage at which V = 77.6 / (22.1 + T[°C]).

c Steinbach et al. (3M), “High-Performance, Durable, Low-Cost Membrane Electrode Assemblies for Transportation Applications,” 2014 Annual Merit Review,

http://www.hydrogen.energy.gov/pdfs/review14/fc104_steinbach_2014_o.pdf

d Based on MEA gross power at 150 kPa abs. Measured at 0.692 V and 90°C, satisfying Q/ΔT < 1.45 kW/°C. At 250 kPa abs status is 0.12 g/kW.

e Measured using protocol in Table P.1.

f Kongkanand et al. (General Motors), “High-Activity Dealloyed Catalysts,” 2014 Annual Merit Review, http://www.hydrogen.energy.gov/pdfs/review14/fc087_kongkanand_2014_o.pdf

g Measured using protocol in Table P.2.

h B. Popov et al., “Development of Ultra-low Doped-Pt Cathode Catalysts for PEM Fuel Cells,” 2015 Annual Merit Review,

http://www.hydrogen.energy.gov/pdfs/review15/fc088_popov_2015_o.pdf.

i D.J. Liu (ANL), “Novel Non-PGM Catalysts from Rationally Designed 3-D Precursors,” 2015 Annual Merit Review, http://www.hydrogen.energy.gov/pdfs/review15/fc118_liu_2015_p.pdf

j Target is equivalent to PGM catalyst mass activity target of 0.44 A/mgPGM at 0.1 mgPGM/cm2.

Recent DOE FCTO Initiatives in Energy Material Network

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ANL, LBL, LANL, NREL, ORNL

Fuel Cell Performance and Durability

ANL, LANL, NREL, ORNL

PGM-free electrocatalysts for next-

generation fuel cells

Examples of Recent Progresses in PGM-free and

Ultralow Pt Catalyst & Membrane Electrode

Developments at Argonne

9

Next Generation PGM-free Catalyst – Addressing Catalyst &

Electrode Designs Simultaneously

10

Improving activity through rationally designed precursors – MOFs/POPs

Improving mass/charge transports through nanofibrous network

Volumetric Activity Turn-Over-Freq. x Site Density

• Argonne’s nano-fibrous network provides higher surface area and nearly exclusive micropores

• New electrode offers enhanced mass transport and charge transfer via a unique micro-macro-porous nano-network

Conventional New ANL design Conventional ANL nano-network

New nano-network architecture not only increases surface area but also site density

New 3-D precursors breaks away from 50-years of square-planar molecular approach

•Argonne introduced Metal-organic-framework & porous organic polymer as next-generation catalyst precursors• “Support-free” and pore-former free •Uniform distribution & high active site

density

“One-Pot” Synthesis of MOF(ZIF)-based TM/N/C Catalysts –

Impact of Ligands

11

(a)

(c)

(b)

(d)Solid State Reaction

ZnO

Fe complexIm mIm

eIm abIm

Different MOFsOrganic Ligands

+

TM/N/C Catalysts

D. Zhao, J.-L. Shui, L. R. Grabstanowicz, C. Chen, S.M. Commet, T. Xu, J. Lu, and D.-J. Liu, Advanced Materials, 2014, 26, 1093–1097 (Frontpiece article)J. Shui, C. Chen, L. R. Grabstanowicz, D. Zhao and D.-J. Liu, Proceedings of

National Academy of Sciences, U. S. A. 2015, vol. 112, no. 34, 10629

D.-J. Liu, J. Shui, C. Chen, US Patent 9,350,026

Simple solid-state synthesis, solvent-free and no separation needed

Very low-cost materials for ZIF synthesis

Versatile process of screening various N-containing ligands

Th

erm

al

Ac

tiva

tion

Fe-doped ZIF Catalyst Activities in Acidic Media were

Evaluated by RRDE and in PEM Fuel Cell

12

0.0 0.2 0.4 0.6 0.8 1.0-6

-5

-4

-3

-2

-1

0

E / V vs. RHE

Cu

rre

nt

De

ns

ity

/ m

A c

m-2 Zn(Im)

2TPIP

Zn(mIm)2TPIP

Zn(eIm)2TPIP

Zn(4abIm)2TPIP

0.0 0.2 0.4 0.6 0.83.5

3.6

3.7

3.8

3.9

4.0

Zn(Im)2TPIP

Zn(mIm)2TPIP

Zn(eIm)2TPIP

Zn(4abIm)2TPIPE

lec

tro

ns

Tra

ns

ferr

ed

E / V vs. RHE

0 500 1000 1500 2000 2500 30000.0

0.2

0.4

0.6

0.8

1.0

Po

wer

Den

sity

/ m

W c

m-2

Current Density / mA cm-2

Cel

l Vo

ltag

e / V

Zn(mIm)2TPIP

Zn(eIm)2TPIP

Zn(4abIm)2TPIP

Zn(Im)2TPIP

0

100

200

300

400

500

600

700

10 100 10000.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

Volumetric current density (A cm-3)

iR-f

ree v

olt

ag

e / V

Zn(mIm)2TPIP

Zn(eIm)2TPIP

Zn(4abIm)2TPIP

Zn(Im)2TPIP

RRDE experiments demonstrated the activity

influenced by ZIF ligands

Such influence is also reflected in MEA /fuel

cell performance testings

T = 80 °CPH2 = PO2 = 1.5 Bar

100% RHO2 saturated 0.1 M HClO4

1600 RPM

Rational Design Combined with Process Optimization Led

to Excellent Fuel Cell Performances in both O2 & Air

0 200 400 600 800 1000 1200 1400 16000.0

0.2

0.4

0.6

0.8

1.0

Current Density (mA/cm2)

Cell P

ote

nti

al (V

)0

100

200

300

400

500

Po

wer

Den

sit

y (

mW

/cm

2)

0 500 1000 1500 2000 2500 3000 3500 4000

0.2

0.4

0.6

0.8

1.0

Current Density (mA cm-2)

Ce

ll P

ote

nti

al (V

)

0

200

400

600

800

1000

Po

wer

Den

sit

y (

mW

cm

-2)

Condition: Pair or PO2= PH2 = 1 bar (back pressure = 7.3 psig) fully humidified; T = 80 °C; N-

211 membrane; 5 cm2 MEA; cathode catalyst = 3.5 mg/cm2, anode catalyst = 0.4 mgPt/cm2.

P = 924 mW/cm2 @ 0.38V

P = 855

mW/cm2 @

0.47V

One-bar Oxygen

P = 437 mW/cm2 @ 0.45V

P = 358

mW/cm2 @

0.54V

One-bar Air

Engineering catalyst morphology and MEA architecture can alter fuel

cell performances between kinetic and mass-transport limited regions

MEA 1 MEA 2MEA 1 MEA 2

Fe-doped ZIF Catalysts Showed Excellent Activities &

Durability in Alkaline Medium

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0.2 0.4 0.6 0.8 1.0 1.2

-5

-4

-3

-2

-1

0

Cu

rre

nt

De

ns

ity

(m

A c

m-2

)

Pt/C, 60 gptcm-2

Zn(eIm)2TPIP

Zn(mIm)2TPIP

Zn(4abIm)2TPIP

Zn(Im)2TPIP

E(V vs. RHE)

10-3

10-2

10-1

100

101

102

0.8

0.9

1.0

1.1

1.2 Pt/C, 60 ugptcm

-2

Zn(eIm)2TPIP

Zn(mIm)2TPIP

Zn(4abIm)2TPIP

Zn(Im)2TPIP

E(V

) v

s R

HE

Kinetic current density (mA cm-2)

0.2 0.4 0.6 0.83.4

3.6

3.8

4.0

Pt/C, 60 ugptcm-2

Zn(eIm)2TPIP

Zn(mIm)2TPIP

Zn(4abIm)2TPIP

Zn(Im)2TPIPEle

ctr

on

s T

ran

sfe

red

E (V vs. RHE)

0 2000 4000 6000 8000 100000

20

40

60

80

100

De

via

tio

n f

rom

in

itia

l i K

(%

)

Cycle Number

Pt/C

Zn(eIm)2TPIP

Zn(mIm)2TPIP

RRDE showed 40 mV improvement over Pt/C at E1/2

Higher Tafel slop than Pt/C observed

O2 saturated 0.1 M KOH

1600 RPM

Electron transfer was less efficient than Pt/C

Durability under voltage cycling surpassed Pt/C

Cycling potential

0 to 1.2 V RHE

0.0 0.2 0.4 0.6 0.8 1.00

1

2

3

4

Co(Im)2

Co(mIm)2

Co(mIm)2/ZIF8

Ele

ctr

ons T

ransfe

rred

n

E (V) vs. RHE

15

Co-ZIFs as Precursors for Fe-free, PGM-free Catalysts

Mitigation of MEA degradation by Fe induced Fenton reaction requires alternative transition metals

In Co-ZIF, Co is also coordinated by N from four imidazole with unit volume packing density as high as 3.6 × 1021/cm3!

High BET surface area ~ 1500 m2/g was achieved in our lab recently 0.0 0.2 0.4 0.6 0.8 1.0

-5

-4

-3

-2

-1

0

Co(Im)2

Co(mIm)2

Co(mIm)2/ZIF8

Curr

ent D

ensity (

mA

/cm

2)

E (V) vs. RHE

E1/2 = 0.75 V

n approach to 4

Co(Im)2 Co(mIm)2 Co/Zn(mIm)2

Co/N4 Coordination Chemistry

Formation of bimetallic MOFs through metal exchange enables the

flexibility of controlling non-volatile TM content

Promising Activity of Co-ZIF Derived Catalyst was achieved

at MEA/Fuel Cell Level

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Condition: PO2 = PH2 = 1 bar (back pressure = 7.3 psig) fully humidified; T = 80 °C; N-211 membrane;

5 cm2 MEA; cathode catalyst = 4 mg/cm2, anode catalyst = 0.3 mgPt/cm2.

1 10 100 10000.6

0.7

0.8

0.9

1.0

Ce

ll P

ote

nti

al

(V)

Cell Current Density (mA/cm2)

OCV = 0.92 V

0 200 400 600 800 1000 1200 1400 16000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Ce

ll P

ote

nti

al

(V)

Current Density (mA/cm2)

IA @ 0.8 V = 28 mA/cm2

iR-free

The Co-only catalyst showed the best-of-the-class performance in a signal fuel cell study

Initial MEA/single fuel cell tests of the catalyst from heat-treated

binary Co(mIm)2/Zn(mIm)2 showed a promising performance

L. Chong, et. al. ChemElectroChem. 2016, 3, 1 – 6, DOI: 10.1002/celc.201600163

Reducing PGM Usage through Synergistic PGM-free/

Ultralow-Pt Catalyst Approach

17

Condition: PO2 = PH2 = 1 bar (back pressure = 7.3 psig) fully humidified; T = 80 °C; N-211 membrane; 5 cm2 MEA; cathode catalyst = 0.9 mg/cm2, anode catalyst = 0.35 mgPt/cm2.

0 1 2 3 4 50.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Current Density / A cm-2

iR-f

ree

Vo

lta

ge

/ V

PGM-free

ANL-2 Pt = 0.039 mg/cm2

ANL-1 Pt = 0.039 mg/cm2

Low-Pt/XC-72, Pt = 0.05 mg/cm2

Commericial, Pt = 0.35 mg/cm2

Fig. 5

Synergetic Catalysis Led to Improvement to Durability

0k

30k

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.50.0

0.2

0.4

0.6

0.8

1.0

iR

-fre

e c

ell

voltge (

V)

Current density / A cm-2

Condition: N-211 membrane; 5 cm2 MEA; cathode catalyst = 0.9 mg/cm2 or 0.039mgPt/cm2

anode catalyst = 0.4 mgPt/cm2, Cycling PN2= PH2 = 1 bar, 100% RH, T = 80 °C, voltage 0.6 V to 1.0 V, testing PO2= PH2 = 1 bar (back pressure = 7.3 psig) 100% RH.

Acknowledgement

Nancy Garland (DOE Fuel Cell Technologies Office) and John Kopasz, Tom Benjamin, for providing slides on recent fuel cell activities under DOE-FCTO

US DOE, Fuel Cell Technologies Office

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