pgm-free oer catalysts for pem electrolyzer...pgm-free oer catalysts for pem electrolyzer di-jia liu...

PGM-free OER Catalysts for PEM Electrolyzer

Di-Jia Liu (lead), Lina Chong, Hao Wang, Argonne National Laboratory Gang Wu, University of Buffalo (Subcontractor) Hui Xu, Giner Inc. (Subcontractor) p157

2019 DOE Hydrogen and Fuel Cells Program Annual Merit Review and Peer Evaluation Meeting, April 30 – May 1, 2019, Washington, D.C.

This presentation does not contain any proprietary, confidential, or otherwise restricted information

Project Overview

Team Lead: Argonne National Laboratory

Sub: U. of Buffalo & Giner Inc.

Project Vision

Award # EE2.2.0.202

Start Date 10/1/2017

Project End Date 09/30/2020

Year 1 Funding* $250k

Year 2 Funding* $375k

To develop platinum group metal-free

(PGM-free) oxygen evolution reaction

(OER) electro-catalysts as viable

replacement for Ir in proton exchange

membrane water electrolyzer (PEMWE)

Project Impact

To support DOE hydrogen production

targets by substantially lowering the

capital and operating cost of PEMWE:

• Cost: $2 / kgH2

• System efficiency: 43 kWh/kgH2 e -

H+

O2 H2O

MOF

PNNE

1.4 1.6 1.80

10

20

30

40

E (V) / RHE

Cu

rren

t d

en

sit

y / m

Acm

-2

OER H2O 2H+ + ½ O2 + 2 e-

*this amount does not cover support for HydroGEN resources leveraged by the project (which is provided separately by DOE)

HydroGEN: Advanced Water Splitting Materials 2

Approach- Summary

Project Motivation

ANL is a pioneer in MOF derived

electrocatalysts for ORR & OER.

UB is a leader in PGM-free

electrocatalyst research.

Giner is an industrial leader in

PEMWE system development.

The team aims at the first commercial

PEMWE using PGM-free OER catalyst

Proposed targets

Metric State of the Art Expected Advance

Overpotentials

against

theoretical

value

Overpotential of

~530 mV @

10mA/cm2 for

PGM-free

catalyst in acid

Overpotential <350

mV or 15 mV higher

than Ir black @

10mA/cm2 in acidic

electrolyte

Current

density in

operating

PEMWE

Non-existing for

PGM-free

catalyst in PEME

PEMWE with

current density >

1000 mA/cm2 @ 2 V

& decay rate < 30

mV/1000 hours

Barriers

Cost: Current PEMWE uses Ir as

OER catalyst with high loading.

Activity: PGM-free catalysts have

shown promising OER activity in

alkaline solution, but not in acid.

Durability: Most catalyst and

support materials are unstable under

high polarization potential in acid.

Partnerships - HydroGen

Computational electrochemistry and

predictive modeling (LLNL and

LBNL)

Advanced electron microscopic

imaging (SNL)

Electrode optimization / catalyst

surface characterization (NREL)


Relevance & Impact – PGM-free OER catalyst for Low Temperature PEMWE

‣ Catalyst cost reduction – Removing the supply and price bottlenecks of precious metal (Ir, Ru, etc.) usage in LTE by replacing them with earthly abundant materials and robust, low-cost syntheses.

‣ HydroGen Mission Alignment – Accelerating low-cost PGM-free OER catalyst for H2 production through advanced LTE.

‣ HydroGen Interaction – Collaborating with four National Labs and five nodes to improve fundamental understanding in OER catalyst development.

Operating principle of PEMWE

Cathode (HER) Anode (OER)

4H+ + 4e- → 2H2 2H2O → O2 + 4H+ + 4e-

H+

e - e -

Cathode

PEM Anode

H2O

H2O

H2O

H2O

O2

O2

O2

O2 H2

H2

H2

H2

H2

High conductivity & smaller footprint

Quick response for renewable sources

High H2 purity & non corrosive electrolyte


To demonstrate high performance, low cost PGM-free OER catalyst in operating PEMWE

Approach – Innovation @ ANL

ANL-a: Co-MOF Derived OER Catalyst

Solvothermal

reaction

Co2+ Controlled

heat

treatment

Organic ligand Co-based Metal-organic Activated Co-MOF (Co-MOF-O)

Graphene-supported

Co-MOF (Co-MOF-G) Graphene-supported activated

Co-MOF (Co-MOF-G-O)

Integrating

graphene

Controlled

heat

treatment

Graphen

e

Oxidized

Co-MOF

Framework (Co-MOF)

• MOF synthesis offers an inexpensive and versatile approach for multi-metallic catalyst development through low-cost metal and ligand exchange

• Framework offers maximal density and exposure of the active site through intrinsic porous structure


Approach – Innovation @ ANL

ANL-b: Porous Nano-Network Electrocatalyst (PNNE)

Electrospinning Catalyst Conversion

• MOF embedded PNNE can improve mass/charge transfers via direct macro-to-micropore connection

• Continuous network offers better connectivity between the catalytic site against deactivation by oxidative corrosion


Approach – Innovation @ UB

Zeolitic Imidazolate Framework


(ZIF-8) based OER catalyst

ZIF-8

High Performance

ZIF-8 catalysts

Approach – Budget Period 2 (BP2) Milestones

Milestone Criteria End Date

Description Status

MOF templated

synthesis for

bimetallic and

multi-metallic

catalysts

Prepare and test at least 4 bimetallic PGM-

free OER catalysts by RDE at ANL and UB.

Fabricate selected catalysts into MEA and

test in PEM electrolyzer at Giner.

12/28/2018

Catalyst structure,

morphology and

active site

characterizations

Complete structural studies using a variety

of analytical tools to better understand

catalytic activity and aging mechanism for

PGM-free OER catalyst in the acidic

environment resulting in mitigation

strategies for decreasing degradation rates

3/31/2019

New Co-based

PNNE catalyst and

Fe-MOF derived

catalyst and MEA

fabrication and

optimization

Complete the synthesis and preparation

>six MEAs containing PNNE OER catalyst

or Fe-MOF based OER catalyst to be

delivered to Giner for PEME test with MEA

performance targeting at current density >

350 mA/cm2 at 1.8 V.

6/28/2019

80% Completed. Recent PEMWE

tests of MEA containing ANL’s

PGM-free OER catalysts

delivered a record current density

of 320 mA/cm2 at 1.8 V.

70% completed: Extensive studies

using XRD, XAS, TEM, EDX,

EELS, have been completed for

two major ANL catalysts. DFT

calculation shows improved

understanding on catalyst

conductivity

20% completed. Two new PNNE-

MOF catalysts were prepared by

ANL. UB sent an OER catalyst to

Giner for PEME test.

Both ANL-a and ANL-b delivered PEM electrolyzer current density of > 200

mA/cm2 @ 1.8 V, exceeding BP 1 goal.

BP2 goal includes doubling current density of > 400 mA/cm2 @ 1.80 V in activity,

and reducing voltage loss of < 100 mV after 100 voltage cycles in durability.


Accomplishments – ANL-a Catalysts Exceed PGM-free Benchmarks & Approach to Ir Black

Activity of ANL-a catalyst approaches The activated catalyst maintained the

to Ir black in acidic electrolyte… morphology of the MOF precursor

… and exceeded PGM-free benchmarks.

Catalysts Overpotential

@10mA/cm2

Ref.

Co-MOF-Gra-O 354 mV This work

Ba[Co-POM] 361 mV Nat. Chem., 2018

Co3O4 570 mV Chem. Mater., 2017

• ANL-a demonstrated lower OER

overpotential than several PGM-free

catalysts reported in the literature,

measured by RDE/half-cell under similar

condition.

• OER potential of ANL-a at 10 mA/cm2 is

only 20 mV to 30 mV higher than that of Ir

black.


Accomplishment – ANL-b Catalysts Exceed PGM-free Benchmarks & Approach to Ir Black

Adding 2nd and 3rd metal into Co-MOF/ ANL-b catalyst showed interconnected

PNNE led to consistent improvement porous framework with better active site

of OER catalytic activity for ANL-b. exposure & improved transports.

1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.80

10

20

30

40 ANL-b

L@ANL-b

LMo@ANL-b

LM@ANL-b

LW@ANL-b

LN@ANL-b

LL@ANL-b

LF@ANL-b

Ir black

E / V vs. RHE

Cu

rren

t D

en

sit

y / m

A c

m-2

HAADF

Co

O

• Multiple bimetallic and trimetallic catalysts were systematically investigated for ANL-b

family, which showed a progressive improvement in OER activity.

• The best ANL-b catalyst has the OER potential of only a few mVs above Ir at 10

mA/cm2, measured by RDE in perchloric or sulfuric acid


Accomplishment – OER Activity & Kinetics of Selected ANL-b Catalysts

Differences of ANL-b OER potentials Tafel plots of ANL-b catalysts versus

over the theoretical value Ir oxide and supported IrOx film

1 101.45

1.50

1.55

1.60

1.65

1.70

Current density / mA cm-2P

ote

nti

al

/ V

vs.

RH

E

ANL-2

LM@ANL-2

IrOx/SrIrO3 films

IrO2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

LF

@A

NL

-b

LL

@A

NL

-b

LN

@A

NL

-b

LW

@A

NL

-b

LM

@A

NL

-b

LM

o@

AN

L-b

L@

AN

L-b

AN

L-b

E / V

vs. R

HE

DEj=10 mA cm-2

DEonset

• Different metal doping in ANL-b catalyst improves surface active site structure and

charge conductivity, therefore significantly enhances OER activity in strong acid

• Low Tafel slope of ANL-b catalysts shows a similar or faster kinetics compared to Ir

benchmarks, which can be attributed to the nanofibrous morphology


Accomplishment – Durability of ANL PGM-free OER Catalysts

1.2 1.4 1.6 1.8

0

20

40

60

80

Cu

rren

t d

en

sit

y (

mA

/cm

-2)

Potential (V vs. RHE)

initial

after 10,000 cycles

24 mV

1.2 1.4 1.6 1.80

20

40

60

80

Cu

rre

nt

de

ns

ity

/ m

A c

m-2

Potential / V vs. RHE

initial

after 10,000 cycles

22 mV

ANL-a Catalyst Ir Black @ 100 ug/cm2

1.2 1.4 1.6 1.8

0

20

40

60

80

Cu

rre

nt

de

ns

ity

(m

A¡¤

cm

-2)


after 10,000 cycle

initial

88 mV

ANL-b Catalyst

Catalyst OER polarizations before & after 10,000 voltage cycles in RDE

ANL-a and ANL-b showed only small voltage lost of 24 mV and 22 mV @ 10 mA/cm2

after 10,000 voltage cycle from 1.2 V to 2.0 V, respectively. Both catalysts demonstrated better stability than low-loading Ir black @ 100μg/cm2

(88 mV) under the same cycling condition. Demonstration of catalyst durability in PEMWE is planned for the next step.


Over 25 MEAs were prepared and tested in PEMWE at Giner.

0 100 200 3001.4

1.5

1.6

1.7

1.8

1.9

2.0

MEA (Oct. 2018, 250 mA/cm2 at 1.8 V)

MEA#1 (Feb. 2019, 320 mA/cm2 at 1.8 V)

MEA#2 (Feb. 2019, 310 mA/cm2 at 1.8 V)

Current density (mA/cm2)

Ce

ll v

olt

ag

e (

V)

0.0

0.1

0.2

0.3

0.4

Imp

ed

an

ce (

Oh

m)

ANL-a

Accomplishment – Membrane Electrode Assembly (MEA) Development & Testing

ANL-a & ANL-b catalyst MEA design & optimization were carried out at ANL.

MEA coated with ANL-a PGM-free OER

catalyst at anode Anode = ANL-a PGM-free catalyst, 2mg/cm2, Cathode = Pt/C,

0.35 mg/cm2, Membrane = N115, 5 cm2 cell, CCM, Testing

condition 60 ˚C, 10 psi DI water at anode

We demonstrated, for the first time, that an operating PEMWE with PGM-free anode

catalyst delivered a current density > 300 mA/cm2 @ 1.8 V, exceeding BP 1 goal!


Accomplishment – Membrane Electrode Assembly (MEA) Development & Testing

PGM-free OER catalyst has different conductivity and surface properties from

conventional FC catalyst, requiring new MEA processing conditions.

Multiple processing parameters (catalyst loading, ionomer ratio, etc.) influence

MEA performance.

0 50 100 150 200 2501.0

1.2

1.4

1.6

1.8

2.0

2.2 ANL-B (no treatment)

ANL-B (with treatment)

ANL-B (modified cat layer)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Current density (mA cm-2)

Vo

ltag

e (

V)

Z

' (O

hm

)

I = 211 [email protected] V



ANL-b

Anode = ANL-a PGM-free, ~1mg/cm2, Cathode = Pt/C, 0.25 mg/cm2,

Membrane = N115, 5 cm2 cell, CCM, 60 ˚C, 10 psi DI water PEMWE setup at Giner

ANL-b catalyst also delivered ~ 300 mA/cm2 @ 1.8 V in operating PEMWE


Accomplishment – ZIF-8 Derived OER Catalysts @ UB

o Addition of TM & carbon nanotubes (CNT) in ZIF-8 increased catalyst durability and activity during 1000 polarization sweeps in 0.1M HClO4.


o Adding urea further improved OER stability for Fe, Co, Mn, Ni doped ZIF 8

1.2 1.3 1.4 1.5 1.6 1.7

0

5

10

15

20

Cu

rre

nt

De

nsity (

mA

cm

-2)


ZIF 8-Fe-CNT before

ZIF 8-Fe-CNT after

0.1M HClO4

900 RPM

OER Polarization

Co Fe Ni Mn

-5

0

5

10

15

Pe

rcen

tag

e D

iffe

rence

(%

)

Transition Metal Addition to ZIF 8-CNT

Percent Change @ 1.7V

-2.72

15.94

12.90

9.95

Percent Difference of Catalyst Before & After Stability Testing

• UB’s MOF catalysts show continuous improvement in OER activity and

stability in acid solution

• A new catalyst has been prepared and shipped to Giner for PEMWE test


Accomplishment – New Polymer Scaffold for PGM-free Catalysts Developed @ UB

o UB’s team also developed a polymer scaffold (PGC) approach showing promise in further improving activity and stability for OER in acid

1.2 1.3 1.4 1.5 1.6 1.7

-1

0

1

2

3

4

5

6

7

Curr

ent D

ensity (

mA

cm

-2)


PGC before

PGC after

0.1M HClO4

900 RPM

OER Polarization

ID/ I

G= 1.19

I

D G

D''

Mn-PANI-Carbon-900 oC

ID/ I

G= 0.76

2DMn-PANI-Carbon-1000oC

ID/ I

G= 0.51

Mn-PANI-PGC-1100 oC

Wave number (cm-1)

Raman

1250 1750 2250 2750 32501000 1500 2000 2500 3000

ID/ I

G= 0.32

Mn-PANI-PPy-PGC-1100 oC

Collaboration with HydroGen @ LBNL – Modeling on Nature of Catalyst Stability & Conductivity

Conductivity change in catalyst by In-gap valence state induced by 2nd element 2nd element doping

O

Co2+

Co3+

DE analysis on 2nd metal

distribution in bulk vs. surface

Band Structure

Ene

rgy

(eV

)

k Points

vs.

M2

vs.

M1 • The M2 in oxide lattice introduce a half

occupied in-gap state, enhancing

electric conductivity

• Energy optimization found that 2nd ion

distributes differently based on size &

charge, impacting catalyst stability and

consistent with the expt’l observation


Collaboration with HydroGen @LLNL – Simulation on Charge Transfer in OER Catalyst

Understanding of electronic properties on ANL OER catalyst through

first-principle calculations

Mid-gap states

• Electronic properties for pristine and doped oxide were established, which

identified the carrier conduction is governed by hole polaron hopping

• Formation of the mid-gap states is due to the hole polaron formation


Collaboration with HydroGen @ SNL – Microscopic Understanding on Morphology to Performance

High resolution STEM and TEM studies on stability/activity improvements

through structural modification in ANL PGM-free OER catalysts

ANL-a

ANL-b

M2 M1

• The STEM shows a conformal TiO2 coating of 1 to 2 nm thick surrounding ANL-a

catalyst particles, serving as protective layer

• The doped metal ions distribute differently based on their sizes and charges in ANL-b,

each plays its own role in promoting catalyst conductivity and stability


Collaboration with HydroGen @ NREL – Surface Analysis on Electronic Structure to Activity

XPS analysis on elemental valance state to Co-MOF catalyst performance

L@ANL-b LF@ANL-b LN@ANL-b LW@ANL-b

• XPS revealed the dependence of Co valance state on the doping element in

ANL’s MOF-derived OER catalysts

• Comprehensive study also identified the electronic structural change of the

critical elements before & after OER voltage cycling


Proposed Future Work

• Continue to explore multi-metallic MOFs through reticular synthesis and post-synthesis modification to further enhance OER catalyst activity and durability in RDE/PEMWE (ANL/UB)

• Continue to investigate the OER catalysts with porous nanofiber network morphology to further improve activity and durability in MEA/PEMWE (ANL)

• Explore surface metal doping (SMD) and atomic layer deposition (ALD) methods to improve PGM-free catalyst stability (ANL)

• Continue to explore metal doping in ZIF-8 and polymer scaffold (PGC) approaches with focus on catalyst activity and durability test in PEMWE (UB)

• Continue to optimize anode design and fabrication to further improve MEA performance in operating PEMWE (ANL/UB/Giner)

• Initiate the MEA/PEMWE durability study using potential cycling (ANL/Giner)

• Continue to improve fundamental understanding on the structure-function relationship of PGM-free OER catalysts using computation modeling and advanced characterization tools through collaboration with HydroGen

BP2 activities will be centered on catalyst performance in operating PEMWE


Project Summary

• Both ANL-a and ANL-b OER catalysts showed excellent activities compared to PGM-free benchmarks, with performance approaching to that of Ir black

• ANL’s OER catalysts also demonstrated promising durability in acidic electrolyte through RDE/halfcell voltage cycling when measured against Ir black

• MEAs containing ANL-a and ANL-b anode delivered current density higher than 300 mA/cm2, representing the first demonstration of PGM-free OER catalyst in the operating PEMWE, and exceeded BP1 goal

• UB team continued to improve activity and durability for ZIF-based OER catalysts and developed a new polymer scaffold (PGC) approach with promising potential

• Computational modeling and structural characterizations by HydroGen nodes provided insightful understanding and critical support to the OER catalyst development

The team demonstrated, for the first time, H2 production from a

PEMWE with PGM-free anodic catalyst at practical operating potential


Acknowledgement

‣ Argonne National Laboratory – Lina Chong, Hao Wang

‣ University of Buffalo, SUNY – Janel Abbott

‣ Giner Inc. – Jason Wiley

‣ HydrogGen Consortium – Lawrence Livermore National Lab (led by Tadashi Ogitsu) – Lawrence Berkeley National Lab (led by Lin-Wang Wang) – Sandia National Lab (led by Josh Sugar) – National Renewable Energy Lab (led by Glenn Teeter & Michael Ulsh)

‣ US DOE Office of Fuel Cell Technologies – Eric Miller – Program Manager – Dave Peterson – Project Manager


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