Highly Active, Durable, and Ultra-Low PGM NSTF Thin Film ...Overview to DOE Catalysis Working Group. Argonne National Laboratory. July 27, 2016. Highly Active, Durable, and Ultra-low

Overview to DOE Catalysis Working GroupArgonne National LaboratoryJuly 27, 2016

Highly Active, Durable, and Ultra-low PGM NSTF Thin Film ORR Catalysts and Supports

1This presentation does not contain confidential information

3M, Energy Components Program:Andy Steinbach

Johns Hopkins University: Jonah Erlebacher

Purdue University:Jeffrey Greeley

Oak Ridge National Lab.:David Cullen

Argonne National Lab.:Debbie Myers, Jeremy Kropf

Project Objective and Relevance

2

Overall Project ObjectiveDevelop thin film ORR electrocatalysts on 3M Nanostructured Thin Film (NSTF) supports which exceed all DOE 2020 electrocatalyst cost, performance, and durability targets.

Project RelevanceORR catalyst activity, cost, and durability are key commercialization barriers for PEMFCs.3M NSTF ORR catalysts are one leading approach which approach many DOE 2020 targets in state-of-the-art MEAs.Project electrocatalysts will be:• compatible with scalable, low-cost fabrication processes.• integrated into advanced electrodes and MEAs which address traditional NSTF challenges:

operational robustness, contaminant sensitivity, and break-in conditioning.

Overall ApproachEstablish relationships between electrocatalyst functional response (activity, durability), physical properties (bulk and surface structure and composition), and fabrication processes (deposition, annealing, dealloying) via systematic investigation.Utilize high throughput material fabrication and characterization, electrocatalyst modeling, and advanced physical characterization to guide and accelerate development.

This presentation does not contain confidential information

Status Against DOE 2020 and Project Targets

Table 1. Status Against TargetsCharacteristic 2020 Target and

UnitsProject Target 2016 Status

Platinum group metal (PGM) total content (both electrodes)

0.125 g/kW 0.1 (0.70V) 0.161

0.182

PGM total loading (both electrodes) 0.125 mg/cm2 0.10 0.1051

0.1272

Loss in catalytic (mass) activity 40 % 20 423

Loss in performance at 0.8 A/cm2 30 mV 20 -83

Loss in performance at 1.5 A/cm2 30 mV 20 -683

Mass activity @ 900 mViR-free 0.44 A/mg (MEA)

0.80 0.283 (NPTF “M”)0.474 (NPTF)0.395 (UTF)

10.015mgPt/cm2 NSTF anode, 0.075 dealloyed PtNi/NSTF cathode, 0.015 mgPt/cm2 cathode interlayer.20.02mgPt/cm2 NSTF anode, 0.091mgPGM/cm2 NPTF “M” cathode, 0.016 mgPt/cm2 cathode interlayer.3NPTF “M” cathode, 0.109mgPGM/cm2 after 30k Electrocatalyst AST cycles.4Annealed NPTF P4A Pt3Ni7/NSTF, 0.12mgPt/cm2; adjusted from 0.900VMEAS (70mV/dec)5Best UTF “A”, 0.027mgPGM/cm2. Average of two MEAs.


Approach – Two Distinct Thin Film Electrocatalyst MorphologiesNanoporous Thin Film (NPTF)

NPTF Approach:1. Structure/composition/process space optimization to

maximize area and minimize leachable TM.2. Proprietary stabilization approaches to minimize

coarsening and TM dissolution.

UTF Approach:1. Structure/composition/process space optimization to

develop highly active, stable, and thin surface facets.2. Maximize NSTF support surface area.

Ultrathin Film (UTF)

NPTF PtNi/NSTF, “P4A, TFA”Status Target

Mass Activity (A/mg) 0.47 0.80Specific Area (m2/g) 19 30

Spec. Activity (mA/cm2Pt) 2.5 2.6

UTF “A”/NSTF, Proprietary ProcessStatus Target

Mass Activity (A/mg) 0.39 0.80Specific Area (m2/g) 15 20

Specific Activity (mA/cm2Pt) 2.5 4.0

BeforeMEA Conditioning State MEA Conditioning State

Before AfterAfter (Dealloyed)


UTF Electrocatalysts

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UTF “A” Electrocatalyst MEA Mass Activity• “A”: First single alloy system

• Initial work - systematic study of composition, structure, and fabrication process levels.

• Mass activity largely monotonic function of key variables.

• To date, best MEA mass activity approaches 0.39A/mg, ~4x higher than Pt/NSTF.

• Characterization by TEM, EDS, EELS, XAFS in progress. Correlations developing.

• Durability evaluation initiated.

UTF H2/Air Performance

0 5 10 150.00.51.01.52.0

Pt PtCoMn UTF

H 2/Air

J @

0.5

V(A

/cm

2 )

SEF (m2Pt/m

2planar)

Various Loadings

• UTF performance >> Pt• High J performance suppressed v.

typical higher loadings

• High J performance dictated by absolute cathode surface area

• UTF TGT: >20m2/g, 0.075mg/cm2

0.0 0.5 1.0 1.50.0

0.2

0.4

0.6

0.8

1.0UTF #3, #4

3x gain over Pt

@ 0.5VPtCoMn

80/68/68oC, 1.5/1.5atmA H2/Air, 2min/ptCell

Volta

ge (V

olts

)

J (A/cm2)

Pt

25-30 µgPGM/cm2

0.00.10.20.30.40.5

Pt/NSTF

Uncorrected for resuidual substrate loading

β

UTF "A" Process LevelORR

Mas

s Ac

tivity

(A/m

g PGM)

α

0.00.10.20.30.40.5

Pt/NSTF

Uncorrected for resuidual substrate loading

UTF "A" Structure ORR

Mas

s Ac

tivity

(A/m

g PGM)

0.00.10.20.30.40.5

ORR

Mas

s Ac

tivity

(A/m

g PGM)

Corrected for resuidual substrate loading

UTF "A" Composition

Pt/NSTF


Cathode electrode PGM loading: ≤ 0.05mgPGM/cm2.

Challenges w/ FC Measurements at Ultralow PGM

• At ultra-low PGM, CV curvature (HER?) makes MEA HUPD integration values questionable.

• New method developed which greatly improves S:N of ECSA as determined by HUPD

• ECSA values calculated with same integration limits with both methods.

• CO stripping may be an alternative; have not evaluated.

0.02mgPt/cm2

0.0 0.2 0.4 0.6 0.8-2

-1

0

1

2 Baseline, MEA1 Baseline, MEA2 New, MEA1 New, MEA2

Shor

t, Cr

osso

ver

Corr

ecte

d J

(mA/

cm2 )

70/70/70C, 0/0psig H2/N2, 800/1800SCCMCV(0.65V->0.085V->0.65V, 100mV/s)

E v. 100% H2 (Volts)

Int Limit

6

0

10

20

30

0

10

20

30

Spec

ific

Area

(m2 /g

Pt) ImprovedBaseline


Task 1 – NPTF Development – Stabilization with “M”

Impact of “M” Integration Method on NPTF PtNi Activity, Performance• Four different “M” integration methods, with several variations within each method.• Mass activity and H2/Air performance @ 1A/cm2 depend strongly on integration method and level.

• To date, method “D” yielding best combination of BOL activity and performance.

0 10 200.00.10.20.30.40.5

0 10 200.20.30.40.50.60.70.8

A B C D A B C D

Mas

s Ac

tivity

(A/m

g)

80oC, 1.5/1.5atmA H2/O2, 100% RH 80oC, 1.5/1.5atmA H2/Air, 68oC DP

Arb. Catalyst Variable Arb. Catalyst Variable

V @

1A/

cm2 (V

olts

)


“M” Integration (Type D) Electrocatalyst AST

• With one “M” integration method, conducted Electrocatalyst AST vs. “M” content• With no “M” (0), > 60% mass activity loss and >40mV loss at 1A/cm2 after AST• With “M”, close to target durability attained and performance for J >0.8A/cm2 improved.


Approach - Electrocatalyst Simulation

DFTSurface energy calculations of Pt skins on Pt alloys

Kinetic Monte Carlo Alloy surface structure predictions

DFTDescriptor binding energies on optimized surface structures

Kinetic predictions of ORR currents from volcano plots and free energies

1. Atomistic determination of catalyst surface structures

2. Activity predictions of optimized surface structures

3. Model Validation

Activity CharacterizationMEARDEFlow cellStructure/Composition CharacterizationHAADF-STEMSTEM+EDSXAFS / ∆µ-XANESWAXSXRDXRF

Electrocatalyst FabricationPVD DepositionProprietary dealloying and annealing processing

HT Methods When Validated

4. Characterization Feedback for Model Refinement9This presentation does not contain confidential information

Electrocatalyst Simulation – DFT of UTF “A”


• Purdue has initiated DFT analysis of the stability and activity of UTF “A” catalysts vs. composition and Pt skin thickness.

• Large surface stresses can develop if substantially strained; depends on Pt skin thickness

• Activity also depends on surface strain and skin thickness ~ up to 20x higher than Pt predicted.

• Model will be tuned based on extensive UTF “A” electrochemical and physical characterization. If validated, will be used for property predictions in new systems.

Electrocatalyst Simulation – KMC of NPTF PtNi

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0.1 1 10 100 10000.2

0.4

0.6

0.8

1.0

Experiment

Pt M

ole

Frac

tion

Cycles

Simulation


• Johns Hopkins has initiated Kinetic Monte Carlo modeling of composition and structure (surface area) evolution of PtNi during electrochemical dealloying (oxidation/reduction cycles).

• Preliminary model results qualitatively consistent with experiment:• Similar sigmoidal composition evolution, slope in transition region, and final composition

• Model will be tuned based on extensive NPTF PtNi dataset. If validated, will be used for property predictions in new systems.

Comparison of composition evolution of experimental NSTF catalyst to simulated

average composition of a ~20nm Pt binary alloy sphere as a function of oxidation/reduction cycle number.

(silver) Pt; (red) oxidized Pt;

(green) Ni.

Approach - High Throughput (HT) Electrocatalyst Development

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HT Electrocatalyst FabricationDeposition• Physical vapor deposition with

appropriate masks.

Dealloying – TBD• Use multi-channel flow cell which

incorporates NSTF catalyst on growth substrate

• Use multi-channel potentiostat to independently dealloy each segment.

• To be developed at JHU.

Annealing – TBD• Proprietary 3M process.

HT Electrochem. Characterization HT Physical CharacterizationXRF (comp.)• 1mm resolution

XRD/WAXS (struct.)• WAXS at ANL APS demonstrated• XRD via benchtop/lab instruments in

development at ANL.

XAFS – TBD• Project will evaluate possibility of in-

operando XAFS of gradient electrocatalysts (ANL)

Segmented fuel cell

• Uses effectively same hardware as standard 50cm2 test cell

• Allows evaluation after standard testing (conditioning, ASTs) with no translation (ideally).

Multi-channel flow cells – TBD• Surface area, ORR activity

determination.• On growth substrate (JHU/3M)

and with catalyst powder (ANL).

Significant first year effort to develop and validate HT fabrication and characterization methods.

S++ Sim. Services


Combinatorial Fabrication and Char. Development

• Analysis of three replicate annealed PtNi gradient catalysts shows good agreement in lattice constant.• One trial showed erroneous results over mid-section – cause TBD.• Lattice constant decreases as Pt mole fraction decreases, as expected.• Analysis for grain size of this series in progress.

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3.603.653.703.753.803.853.90

0.00.20.40.60.81.0 0.00

0.05

0.10

FCC

Latti

ce C

onst

(Ang

)

Annealed

Position (arb)

Standard Deviation of 3 TrialsAverage/Max RSD: 2.6/6.5%

Position (Arb)

Pt M

ole

Frac

tion

Annealed

3 Tr

ial S

td. D

ev (A

ng)

WA

XS a

t AN

LXR

F at

3M


Task 3 - Combinatorial Electrocatalyst Fabrication and Characterization Development – Segmented ECSA

• Pure Pt, loading gradient (20-50ug/cm2), bottom to top.

• Very low roughness factors of ~1-2cm2

Pt /cm2planar required

significant method development (software!)

• Detected roughness factor agrees well between segmented cell and homogenous cell.

• Some challenges with reliability of cell setup. Debugging in progress.

0

20

40

601.00 1.25 1.50 1.75 2.000 10 20 30 40 50 60

0

1

2

0 1 2 3 4 5 6

0 2 4 6 8 10

0

2

4

6

8

10

x: Net Cathode Flow Direction→

y: Decreasin

g P

t Lo

ad→

1.000

1.250

1.500

1.750

2.000

2.000

SEF (cm2/cm2)

x va

riab

leN

on

e

SEF (cm2/cm2)

Ho

mo

gen

ou

s ME

A M

easurem

ents

y variableLoading (µg/cm2)

SE

F (

cm2/

cm2)

Spec. Area (m2/g)

14

CVs of 121 segments, homogenous MEA


Summary

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• UTF and NPTF stabilization approaches are promising• UTF “A”: Up to 0.39A/mg, in MEA (ca. 4x Pt/NSTF). Significant sensitivities to composition, structure,

processing. Durability assessments initiated.• NPTF PtNi+”M”: Electrocatalyst AST durability target largely achieved. Mass activity improving.

• Electrocatalyst Simulation• DFT

• Simulations of first Pt alloy system with varying subsurface compositions and Pt skin thicknesses revealing key trends in both stability and activity.

• Correlations to project experimental data in progress.• kMC

• Initial PtxNi1-x surface area and composition evolution simulations agree reasonably well with experiment

• HT Development• HT electrocatalyst fabrication and composition and structural characterization methods validated.• HT electrochemical characterization development in progress. Showing good promise.


Highly Active, Durable, and Ultra-Low PGM NSTF Thin Film ...Overview to DOE Catalysis Working Group. Argonne National Laboratory. July 27, 2016. Highly Active, Durable, and Ultra-low

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