synthesis and characterization of nitrogen doped reduced

Synthesis and Characterization of Nitrogen Doped Reduced Graphene Oxide Based Cobalt-ZIF-8 Catalysts for Oxygen

Reduction Reaction

Title: Synthesis and Characterization of Nitrogen Doped Reduced Graphene Oxide Based Cobalt-ZIF-8 Catalysts for Oxygen Reduction ReactionAuthors: H. Shirzadi Jahromi, S. Saxena, S. Sridhar, M. K. Ghantasala, R. Guda (Western Michigan University), E. Rozhkova, and K. Suthar (Argonne National Laboratory)

Slide 2240th ECS MeetingSession: I01A Polymer Electrolyte Fuel Cells & Electrolyzers 21 (PEFC&E 21) -Diagnostics/Characterization Methods, MEA Design/Model.Publication ID: I01A-1024

Introduction| Who are we

Hassan Shirzadi Jahromi

Sudharsan Sridhar

ShiviSaxena

Dr. Ramakrishna Guda

Dr. Muralidhar K. Ghantasala

Dr. Elena Rozhkova

Dr. Kamlesh Suthar



Agenda

https://afdc.energy.gov/sp/assets/car_pages/hydrogen-ef5e5e351e15df47f1681bae5c9b82869e41b1467ea878d9093d543b74da9593.jpg

• Introduction

• Synthesizing Samples

• Characterization of the Samples

• Electrochemical Measurements

• Conclusion



Introduction| Fuel Cell Catalysts

• Platinum

• Transition metals

• Carbon-based Catalysts

• Combination of Carbon, Transition Metals - MOF

https://img.fuelcellsworks.com/wp-content/uploads/2019/07/Improved-Fuel-Cell-Catalys.jpg https://www.researchgate.net/profile/Osama-Ayadi/publication/336232647/figure/fig1/AS:809872803258370@1570100131259/Basic-structure-of-PEM-fuel-cell.png



Synthetic scheme of Nitrogen doped Reduced Graphene Oxide

(i)H2SO4 ,(ii) KMnO4 , Stir (12h)Nitrogen dopedGraphene Oxide

Graphite Flakes + NaNO3(ice-bath)

(iii) C3H6N6 (Melamine), Stir (12h)

(i)H2O2 ,(ii) Dry

(iii) 2HN-NH2

Nitrogen dopedReduced Graphene

Oxide

Synthetic scheme of Cobalt doped ZIF-8

Methylimidazole+ Co(NO3)2.6H2O

(MeOH as solvent)

(i)Stir (2hr, RT) ,(ii) ZnNO3.6H2O

(iii) Centrifuge, (iv) Wash

Cobalt doped ZIF-8

Experimental Section| Synthesising Samples



Synthesis of N-Gr-Co-ZIFx and Gr-Co-ZIFx & Pyrolyzing at 600 C

Co-ZIF8 +MeOH(Sonicated for 5hr)

N-Gr/ Gr +MeOH(Sonicated for 3hr)

+

(i) Stir Overnight(ii) Centrifuge, ppt

(iii) Wash (DI, EtOH),(iv) Dry

N-Gr- Co-ZIF/ Gr-Co-ZIFx

Pyrolysis (600ºC,Argon (2hr)

N-Gr- Co-ZIF/ Gr-Co-ZIFx-600

Experimental Section| Synthesising Samples



Results and Discussion| Characterization of Samples

X-ray diffraction (XRD)

Scanning Electron Microscope (SEM)

https://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/FTIR_Spectrometer_%2B_ATR.jpg/330px-FTIR_Spectrometer_%2B_ATR.jpg

Fourier-transform infrared spectroscopy (FTIR)

Raman spectroscopy

https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/SEM_chamber1.JPG/330px-SEM_chamber1.JPG

http://www.snlabs.com/images/RAMAN_S.jpg

https://upload.wikimedia.org/wikipedia/commons/thumb/3/30/Freezed_XRD.jpg/450px-Freezed_XRD.jpg




Scanning Electron Microscope (SEM)

• More porous Gr-Co-ZIF0.9 after carbonization.

• Grain size reduction (~20%) in Ge-Co-ZIF0.9 after carbonization.

• 20-25% grain size reduction after carbonization in N-Gr-Co-ZIF0.9.

SEM image of (a) Gr-Co-ZIF0.9, (b) Gr-Co-ZIF0.9-600, (c) N-Gr-Co-ZIF0.9 and (d) N-Gr-Co-ZIF0.9-600 samples.




Fourier-transform infrared spectroscopy (FTIR)

• Ring stretch frequency of ZIF-8 observed for all samples

• Lower peak intensity of C=N

In absence of nitrogen

• The IR peaks within 420-425 cm-1

region are assigned to Zn-N (ZIF-8).

• A peak shift by increasing

the Co/Zn ratio.

Comparison of FTIR for (a) Gr-Co-ZIF0.9, (b) Gr-Co-ZIF0.9-600, (c) N-Gr-Co-ZIF0.9 and (d) N-Gr-Co-

ZIF0.9-600 samples.

Metal-Nitrogen peak comparison with different loading of Cobalt in

FTIR.




Raman spectroscopy

• Carbonization and nitrogen doping effects on Raman Spectra.

• Higher ID/IG ratio is indicative of more defects in the sample.

• Highest value for ID/IG ratio for the N-Gr-Co-ZIF0.9-600.

• Higher ID/IG ratio after carbonization.

Raman spectra showing D and G bands for synthesized materials, confirming the doping

process and pyrolyzing with increasing ID/IG ratios

ID

Wavelength (cm-1)

IG

Wavelength (cm-1)

ID

(a.u.)IG

(a.u.)ID/IG

N-Gr-Co-ZIF0.9 1315.5 1597.1 963.9 847.7 1.13

N-Gr-Co-ZIF0.9-600 1337.1 1597.9 399.5 309.6 1.29

Gr-Co-ZIF0.9 1315.5 1597.1 663.1 546.2 1.21

Gr-Co-ZIF0.9-600 1303.7 1599.8 1816.5 1419.9 1.27




X-ray diffraction (XRD)

• Study the effect of Nitrogen doping and carbonization on Crystallinity.

• similar peak pattern with different intensities for all samples.

• Lower intensities after carbonization in the XRD

• Crystallinity might have been affected along with a reduction in grain size and increase in porosity.

• Limited effect of Carbonization at 600 C

• May require higher temperature.

• Not significant effect on crystallinity by Nitrogen doping.

Powder XRD patterns for (a)Co-ZIF0.9, (b)Co-ZIF0.9-600, (c)N-Gr-Co-ZIF0.9, (d)Gr-Co-ZIF0.9, (e)N-Gr-Co-ZIF0.9-600,

(f)Gr-Co-ZIF0.9-600 samples.



Experimental Section|Electrochemical Measurements

Electrochemical Measurements

• AB bipotentiostat, Pine Chem USA

• Ag/AgCl (KCl-saturated) - Reference Electrode

• Pt Disk- Counter Electrode

• 0.1 M HClO4 - Electrolyte

• PineChem Glassy Carbon - Working Electrode

• Oxygen and Nitrogen Saturated



Results and Discussion| Oxygen Reduction Reaction

INK preparation

• pre-mixing 5.0 mg of the sample in 212.5 µL isopropyl alcohol (IPA) and 150 µL 5 wt% Nafion solution in required amount of water and ultrasonicating in ice bath for 60 min.

• 10 μL of the catalyst ink was deposited on the cleaned glassy carbon electrode( 5mm ) with catalyst loading of 255.10 μgcm−2 and allowed to air dry




Cyclic Voltammetry (CV)

• Cyclic voltammogram for 40 wt% Pt/C catalyst.

• A pair of broad redox peaks in N2 and O2 conditions.

• Relatively larger and clear ORR peak at 342 mV in the presence of Oxygen.

Comparison of CV plots for 40 wt% Pt/C catalyst purged in nitrogen and oxygen.




Comparison of CV plots for different Co-MOF samples purged in oxygen


• A better ORR peak for N-Gr-Co-ZIF0.9 relative to the

Co-ZIF0.9 and Gr-Co-ZIF0.9 .

• 55% and 83% higher area under the curve for

Gr-Co-ZIF0.9-600.

• Highest power density in Gr-Co-ZIF0.9-600.

• More visible ORR peak in N-Gr-Co-ZIF0.9-600.

• Increase in potential of ORR peak by adding Gr and N-Gr.

• Nitrogen doped Reduced Graphene Oxide

enhanced the catalytic performance.





• The effects of carbonization on CV plots for Reduced Graphene Oxide-MOF samples.

• 41% increase in the area under the curve.

• 11 mV increase in ORR potential.

CV plots of Gr-Co-ZIF0.9 samples before and after carbonization purged in nitrogen and oxygen




CV plots of N-Gr-Co-ZIF0.9 samples before and after carbonization purged in nitrogen and oxygen.


• Carbonization effects on the CV plots of nitrogen doped reduced graphene oxide-MOF samples.

• 23% increase in the area under the curve.

• 58 mV increase of the cathodic potential.




Comparison of CV plots for N-Gr-Co-ZIF0.9-600 and Gr-Co-ZIF0.9-600 purged in nitrogen and oxygen


• Nitrogen doping Decreases area under the curve.

• 23 mV and 63 mV lower potential than that of Pt/C catalyst, for N-Gr-Co-ZIF0.9-600 and Gr-Co-ZIF0.9-600respectively.



Conclusion

• The structural and chemical properties of the synthesized materials obtained by FTIR, SEM, EDS, Raman and XRD .

• A reduction in grain size and increased porosity noted after carbonization.

• Most striking C=N stretching vibrations detected in N-Gr-Co-ZIF0.9-600.

• Highest number of defects observed in N-Gr-Co-ZIF0.9-600 sample.

• Reduced crystallinity observed after nitrogen doping and carbonization.

• Enhancing the catalytic performance of the investigated samples due to incorporation of Reduced Graphene Oxide.

• Increase in Catalytic performance of the samples with pyrolysis.

• N-Gr-Co-ZIF0.9-600 showed excellent catalytic activity, and high selectivity for ORR in acidic medium.

The Carbonized Nitrogen Doping of Reduced Graphene Oxide Metal Organic Framework materials with Cobalt inclusion showed potential for use as a fuel cell catalyst material.



Acknowledgement

Access to facilities at Center for Nanoscale Materials was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357.

Contact:❑ Email: [email protected]❑ LinkedIn: https://www.linkedin.com/in/hassan-shirzadi/

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synthesis and characterization of nitrogen doped reduced

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