ElectroCat: Developing Platinum Group Metal-Free Catalysts for Oxygen Reduction Reaction in Acid: Beyond the Single Metal SiteFree Catalysts for Oxygen Reduction Reaction
in Acid: Beyond the Single Metal Site
P. I. Qingying Jia
06/08/2021
DOE Hydrogen Program AMR Project ID#: FC302 2021 Annual Merit Review and Peer Evaluation Meeting
This presentation does not contain any proprietary, confidential, or otherwise restricted information
Project Goals
activity and power density in PEMFCs.
• Develop PGM-free catalysts with high site density and utilization for improved activity and power density in PEMFCs.
• Understand active site formation, nature, and degradation of Fe-N-C catalysts.
The cost-effective and efficient PGM-free catalysts developed by this project, if succeed, may be used in PEMFCs to facilitate its large-scale and sustainable deployment.
2
Overview
Timeline
• Northeastern University Sanjeev Mukerjee
Development of M(x) -N-C catalysts with improved turnover frequency (TOF) and/or catalytically-active
site density.
Synthesis of M(x) -N-C catalysts via surface deposition methods to bypass the pyrolysis to achieve (1)
well-defined model catalysts, (2) alternative synthesis route, and (3) understanding of active site
formation mechanism.
activity loss ≤ 40 ≤ 40
Loss in power density Percentage
power loss - ≤ 50
4
Approach
Synthesis 1. Room/low temperature synthesis of M-N4 sites (100%) 2. Wet impregnation with innovative MMA precursors (80%) 3. Chemical vapor deposition (CVD) (100%) 4. Ionothermal carbonization (70%) 5. Ion Beam-Assisted Deposition (IBAD) (90%) 6. Flash pyrolysis (80%)
Characterizations Spectroscopy: in situ XAS, Mossbauer, XPS, NMR, XRD Microscopy: SEM, HAADF-STEM, HRTEM
ORR performance evaluation RDE, PEMFC
Site density evaluation Cyclic Voltammetry, Nitride stripping, NO stripping, Mossbauer
Mass transport modeling
NC-ArNH3
HT at ~200 oC to stabilize
the M ions absorbed
0.1 M HClO4
FeOx rather than single-atom FeNx formed upon LT synthesis and it exhibits instable ORR activity in acid. 6
Accomplishments and Progress
H NMR
XANES confirms the Co in (CoN3)2OH-O2 is at the oxidation state of +3,
rather than +2 observed for all previous Co-Nx sites. FT-EXAFS indicates Co-
Co bond distance comparable to that of Co(OH)2, and Co-N/O distance
comparable to that of Co(II)Pc. We interpret these results as the OH bridge
two Co-Nx sites making the Co at +3 without altering the Co-N structure.
Co(ClO4)2+ methanol
Co(ClO4)2 + Fe(ClO4)2
improve the activity is undergoing.
Path R (Å) N σ2 (Å2)×10-3
Co-N/O 1.91(1) 4.4(6) 9(2)
Co-C 2.77(2) 8(1) 9(2)
-
- -
- -
90% Fe(III) FeCl3 is chosen as the precursor for CVD
due to its low boiling point of 316 . Thermochimica Acta, 2010, 497, 52
No Fe(II)-N4
O2 -Fe(III)-N4
N C < 6 ppm 2.16 4.23 84.00
NC CVD 750 < 6 ppm 1.75 4.18 79.35
FeNC CVD 750 2.00 0.12 4.24 85.48 TPR: ZnCl2
After the CVD, NO
significant changes on the
FeCl3 (g)+ Zn-N4 → Fe-N4 + ZnCl2 (g)
Transmetalation mechanism on the formation of Fe-N4 sites during CVD is identified. 8
H2 -air
E1/2=0.85 V
H2 -O2
H2 -O2
5 cm2 MEA; Cathode: 6 mg/cm2, Anode: 0.3 mgPt/cm2; H2: 200 ml/min; O2:
1000 ml/min; PO2 = 1 bar partial pressure, 100% RH, 80 ; Nafion-212. = PH2
~45% activity loss after 3 full
scans in H2-O2 PEMFCs.
~34% power density (0.45
scans in H2-air PEMFCs.
F, indicating good integration
phase & catalytic/electron-
conducting phase.
FeNC-CVD-750 delivers 33 mA·cm-2 at 0.9 V in H2-O2 PEMFCs and 0.45 W·cm-2 in H2/air, but rapid degradation. 9
No D2
Nitrite stripping
NO stripping
Fe content: 2 wt%
TOF(0.8 V) = 0.8 e -·site-1·s -1
Normally higher Fe wt% of Fe-N-
C leads to lower U, limiting
SDmass. This issue is alleviated by
CVD that exclusively forms gas-
and proton- accessible Fe-N4
via transmetalation.
Energy Environ. Sci., 2020,13, 2480 SDmass = 1.9×1020 sites·g-1
Record high (~1020) catalytically-active site density verified by four different methods, accounting for the high ORR activity. 10
Accomplishments and Progress
Tafel in Cathode
• The model can predict the cell performance for various O2
concentrations
• Transport limited behavior observed in air-based cathode due to
lower O2 concentrations
kinetics
FeNC-CVD-750 to that of
poor ORR kinetics, in
agreement with TOF study.
the PEMFC performance.
Developed predictive modeling capabilities to capture ORR performance in both RDEs and PEMFCs. 11
Accomplishments and Progress
and low porosity
• Higher ohmic losses in O2 electrode due to higher cathode
thickness
interface
Voltage breakdown analysis
Lower performance
Very high ohmic loss (dry membrane)
Transport gains not enough to compensate
The modeling shows that the ORR activity of FeNC-CVD-750 is mainly limited by ORR kinetics. 12
Accomplishments and Progress
CVD@750 + + XCl
Ball milling
Molten salt (XCl, X=Li, Na, K, Cs) added to:
• Remove Zn from ZIF-8 at lower temp via ZnCl2
(732 ) rather than Zn (907 ) sublimation.
• Tuning the morphology and porosity of N-C.
• Alleviate demetalation of Fe-N4.
Substantial degradation observed within 40 cycles, • Better control over the morphology of N-C. due primarily to full exposure of Fe-N4 sites by CVD.
O2 -0.5 M H2SO4, 0.6-0.95 V (3s)
Fe dissolution
NaCl
A shift of 23-30 mV observed after 20K cycling; 6-10 mV recovered by refreshing the electrolyte.
Improved durability with comparable activity is achieved by ionothermal carbonization. 13
Accomplishments and Progress
• Scientific challenge: RT/LT synthesis of M-N4.
• Concept: using high energy beam of IBAD alternative
to high temperature to drive the formation of M-N4.
• Engineering challenge: deposition Fe evenly onto
highly porous powders.
deposition.
Target mass
precursor (g)
Fe deposition
thickness (Å)
Large metallic Fe nanoparticles observed for all cases.
IBAD deposition on powders up to 200 implemented, but no M-N4 site formation identified. 14
Accomplishments and Progress
Response to Previous Year Reviewers’ Comments
This project has not been previously reviewed at an AMR because of COVID-19.
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Northeastern University (University Prime)
Qingying Jia (PI), Sanjeev Mukerjee (Co-PI), Lynne LaRochelle Richard, Li Jiao, Qiang Sun
Catalyst design and characterization, in situ XAS, mechanism and degradation studies, MEA
fabrication and testing, management and coordination.
Lawrence Berkeley National Laboratory (National lab sub)
Adam Weber (Co-PI), Lalit Pant
Mass transport modeling
Argonne National Laboratory (EMN Consortium Member)
Deborah J. Myers, Jae Hyung Park, Magali Ferrandon, Evan Wegener, A. Jeremy Kropf
In-temperature XAS, TPR, NO stripping, brainstorming
Oak Ridge National Laboratory (EMN Consortium Member)
Dave Cullen, Karren More
Hui Xu, Fan Yang, Sichen Zhong, Thomas Stracensky
PEMFC testing and MEA fabrication
Institut Charles Gerhardt Montpellier (University unfunded partner)
Frederic Jaouen, Jingkun Li, Moulay Tahar Sougrati
CVD, Mossbauer, ex situ XAS, brainstorming
Thin-films Research, Inc (Local industry sub-contractor)
T.R. Raghunath
IBAD 16
Remaining Challenges and Barriers
• Further improve the activity of at least one type of Fe-N-C catalysts to 0.035 A·cm-2 and
above at 0.9 V in H2-O2 PEMFCs.
• Further improve the powder density of Fe-N-C catalysts to 0.5 W·cm-2 in H2-air PEMFCs.
• Improve the durability of Fe-N-C catalysts to ≤ 50% activity loss upon AST.
• Make FeCoN6-OH-O2 and (FeN3)2-OH-O2 catalysts based on (CoN3)2-OH-O2 for improved
activity and durability.
These four challenges will be tackled by optimizing FeCoN6-OH-O2 catalysts with improved TOF
and FeNCXCl -CVD-750 catalysts with improved site density, mass transport, and durability.
• Understand the degradation mechanism of Fe-N-C catalysts and electrodes in PEMFCs.
By studying the degradation modes of FeNCXCl -CVD-750 catalysts with different pore size and
distribution and different degradation behaviors.
17
Advance ionothermal carbonization to further improve the activity and durability of Fe-N-
C catalysts. 1. improve site density by enriching the nitrogen content with lower temperature pyrolysis of N-C.
2. improve mass transport by tunning the pore size and distribution.
3. improve the durability by tunning the pore size and distribution and functionalizing the carbon.
4. improve the understanding of Fe-N4 degradation mechanism.
Synthesize FeCoN6-OH-O2 and (FeN3)2-OH-O2 catalysts.
Identify MMC sites via STEM and in situ XAS.
Conduct mass transport modeling to understand the bases of the activity and durability of
catalysts (with MMC sites) with high PEMFC performance.
Any proposed future work is subject to change based on funding levels.
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Summary
activity loss ≤ 40 ≤ 40
Loss in power density Percentage
power loss - ≤ 50
34% at
1,000 cycles
Major Accomplishments
The CVD was pioneered as a new synthesis route to make highly active Fe-N-C catalysts with record-high site density.
Synthesis of di-nuclear metal centers was achieved.
Fe-N4 site formation mechanism (transmetalation) was verified.
The Fe-N4 evolution pathway during pyrolysis was reavealed by in-temperature XAS.
19
Acknowledgements
Yu Huang, Zipeng Zhao
Technologies Office (HFTO)
National Renewable Energy
Full Patent Application: No.: PCT/US2020/058362; Title: Fe-N-C Catalysts Synthesized by Non-
Contact Pyrolysis of Gas Phase Iron; Reference No.: INV-20028. PCT Application filed on
10/30/20
We are in the process of licensing the above patent to Advent Technologies for the synthesis of
PGM-free catalysts.
We plan to expand the CVD method (patented) to the synthesis of other PGM-free catalysts for
other applications.
Simulated H NMR
A possible structure of (CoN3)2OH-O2
Although the peak around 2 overlaps that of Co foil, its arising from the Co-Co bond
can be ruled out by the FT-EXAFS spectra at the Real and Imaginary spaces.
Note the absence of the peak around 2.7 (the Co-Co bond in (CoN3)2OH-O2) in the
ZIF8-derived Co-N-C with predominately Co-N4 sites.
Further support of the di-nuclear Co-Co configuration. 23
Technical Back-Up
In-house ZIF-8 N-C FeNC-CVD-750
Zn-N4
Zn-N4
Fe-N4
-
- -
- -
- -
- -
-
- -
- -
- -
- -
ICP Fe (wt%) Zn (wt%) N (wt%) C (wt%)
N C < 6 ppm 2.16 4.23 84.00
FeNC CVD 650 2.25 1.05 3.97 85.42
FeNC CVD 750 2.00 0.12 4.24 85.48
FeNC CVD 900 3.76 0.23 3.32 85.42
FeNC CVD 1000 2.72 0.03 2.36 84.20
ICP Fe (wt%) Zn (wt%) N (wt%) C (wt%)
N C < 6 ppm 1.76 4.64 86.85
NC CVD 650 < 6 ppm 1.76 4.23 80.69
NC CVD 750 < 6 ppm 1.75 4.18 79.35
NC CVD 900 < 6 ppm 1.61 4.30 80.69
NC CVD 1000 < 6 ppm 1.19 3.98 83.59
Vapor evolution
of FeCl3
Unlike CVD with FeCl3, the removal of Zn did not
occur until 1000 during the CVD without FeCl3,
which supports the transmetalation mechanism
wherein Fe replaces Zn forming Fe-N4. The replaced
Zn is removed by sublimation of ZnCl2 (732 )
rather than Zn (907 ). At 650 below the boiling
point of ZnCl2, no CV capacitance improvement and
worse ORR activity, indicating less transmetalation.
FeCl3 gas reaches the highest pressure at ~700 .
At even higher temperature, N content drops.
Therefore, 750 is likely close to the optimal CVD
temperature. 25
- - -
· - · -
-
–
-
Jaouen et al. ACS Catal. 2019
Ref IS (mm s 1) QS (mm s 1) Assignment Fe
precursor
Mössbauer
Measurement
environment
J. Phys. Chem. C 2012,
116, 16007, 16001 1.06 3.99
HS Fe(II), FeN4
Adv. Energy Mater. 2019, 9,
1902412. 0.63-0.71 3.84-3.92
HS Fe(II)N4
HS Fe(II)
trapped in
Nafion ionomer
in situ
Chem. Phys. Lett. 9, 390
392 (1971) 1.15 3.0 FeCl2·4H2O std FeCl2·4H2O ex situ RT
FeCl2·2H2O Rokuhnite
(JCPDS 00-025-1040) 1. By far, D3 was observed only in the Fe-N-C catalysts
either made by using iron chloride precursors (red)
CVD or in contact with acidic media (blue).
2. hydrated FeCl2 was observed after TPR.
3. The IS and OS values of D3 close to those of
FeCl2·4H2O standard.
The lack of D2 indicates that all Fe-N4 sites formed upon We therefore assigned the D3 in FeNC-CVD-750 to CVD is accessible by air and in the form of O2-Fe-N4 (D1) FeCl2·4H2O. It can also be FeSO4·xH2O or FeSO3 for ex situ, accounting for full utilization of Fe-N4 sites. other cases. 26
Technical Back-Up
Parameter Value
GDL thickness 190 MPL thickness 45 Anode catalyst layer (CL) thickness 10 Cathode catalyst layer thickness 115 Membrane thickness 40 Anode/cathode channel RH 100%
Anode/cathode channel temperature 80 C
Anode/cathode channel pressure 150 kPa
Anode catalyst specific area (ECSA) −15.4 × 106 m
Anode CL porosity 60%
Cathode ionomer volume fraction 25%
Anode ionomer volume fraction 18%
Cathode agglomerate radius 80 nm
Cathode exchange current (low slope region) −1Fitted: 1.25 × 10−8 mA ⋅ μg Cathode exchange current (high slope region) −1From RDE: 4.56 × 10−6 mA ⋅ μg Cathode catalyst loading −2Fitted: 240 mg ⋅ cm Cathode agglomerate film thickness Fitted: 8 nm
Cathode CL porosity Fitted: 35%
Membrane vapor equilibrated protonic conductivity Fitted: Shown in Eq. (S11)
Membrane liquid equilibrated protonic conductivity Fitted: Show in Eq. (S12)
27
Nitrite stripping
In literature by far, the SDmass and TOF were calculated based on 5 e- (n=5) pathway
Fe(III)-N4-NO + 5e- + 6H+ → Fe(III)-N4 + NH4 + + H2O; n=5; Nat. Commun. 7, 13285 (2016)
[ −2 × [ −1 . = = 1.0 × 1020 · −1
× [ −1 × [ −1
− ) × [ −1
− 2 = = 0.47 − −1 −1
(2 −)[ −1 × [ −1
pH 5.2
270 μg/cm2
Fe(III)-N4-NO + 3e- + 3H+ → Fe(III)-N4 + NH2OH; n=3; Nat Commun 12, 1856 (2021)
Energy Environ. Sci., 2020,13, 2480
FeNC-CVD-750 exhibits record-high SDmass and comparable TOF. 28
Technical Back-Up
FeNCCsCl -CVD-750 durability evaluation
800 μg/cm2, Steady-state, 900 RPM, O2-saturated 0.5 M H2SO4, 0.6-0.95 V (3s)
FeNCCsCl -CVD-750 exhibits improved durability than FeNC-CVD-750 in RDEs. 29
single-atoms on porous substrate is seen.
Co-edge
No Co redox transition until 1.0 V. The local structure is CoPc-like but distorted.
Fe-edge
Highly distorted Fe-N4 with regular redox shift.
Flash pyrolysis does not lead to the formation of di-nuclear CoFe-sites and high ORR activity. 30
Publications and Presentations
Publications
• Jiao, L.; Li, J.; Richard, L.; Sun, Q.; Stracensky, T.; Liu, E.; Sougrati, Z.; Zhao, Z.; Yang, F.; Zhong, S.; Xu, H.; Mukerjee, S.; Huang, Y.; Cullen, A. D.; Park, J.; Ferrandon, M.; M. Myers, D.*, Jaouen, F.*, and Jia, Q*. Chemical vapor deposition of Fe-N-C oxygen reduction catalysts with full utilization of dense Fe-N4 sites. 2nd Minor Revision under review by Nat. Mater.; Preprint available on ChemRxiv
• Li, J., Jiao, L., Wegener, E., Richard, L., Liu, E., Zitolo, A.,Sougrati, M., Mukerjee, S., Zhao, Z., Huang, Y, Kropf, A., Jaouen, F., Myers, D*., and Jia, Q*. Evolution pathway from iron compounds to Fe1(II)-N4 sites through gas-phase iron during pyrolysis, J. Am. Chem. Soc. 2020, 142, 1417-1423. (Highly cited Paper)
Conference Presentations
• Q. Jia, L. Jiao, J. Li, T. Stracensky, M. Sougrati, S. Mukerjee, F. Jaouen, D. Myers. Move beyond the evolution pathway for the formation of M-N4 sites upon pyrolysis of the mixture of M, N, and C precursors, PRiME 2020
• Q. Jia, J. Li, D. Myers, A. J. Kropf, S. Mukerjee. Revisiting the Nature of Active Sites in Pyrolyzed Fe-N-C Electrocatalysts: In Situ Monitoring the Structure Evolution of Active Sites in Fe-N-C Catalysts during Pyrolysis. 235th ECS Meeting, 05/26/2019 (Invited)
• L Jiao, E Liu, LLR Richard, S Mukerjee, Q Jia. Developing Platinum Group Metal Free Catalysts with Multiple Metal Centers for the Oxygen Reduction Reaction in Acid, 235th ECS Meeting
• LLR Richard, L Jiao, E Liu, Q Jia. Development of Bimetallic Non-Platinum Group Metal Catalysts Based on Metal Organic Framework Precursors, 235th ECS Meeting
• S. Mukerjee, Q. Jia., Structural and Mechanistic Basis for the Oxygen Reduction Activity of Pyrolyzed Fe-N-C Electrocatalysts. 235th ECS Meeting
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