1. Platinum nanoparticles-cobalt oxide nanostructures as efficient binary catalyst for ethylene glycol electro-oxidation
Ghada H. El-Nowihy
Chemical Engineering Department, Faculty of Engineering, The British University in Egypt
Supervisors
Prof. Mohamed S. El-Deab
Chemistry Department, Faculty of Science, Cairo University
Prof. Ahmad M. Mohammad
Prof. Mostafa M. H. Khalil
Chemistry Department, Faculty of Science, Ain Shams University
Prof. Mohamed A. El-Shahir

2. Outline Fuel Cells: Essence and Motivation
Direct Ethylene Glycol Fuel Cells (DEGFCs)
Limitations and Means of Overcoming
Experimental
Results & Discussion
Conclusions

3. Energy Crisis & Alternative Energy Sources
Solar energy
Wind energy
Hydroelectric energy
Geothermal energy
Bioenergy
Fuel cells energy

4. Fuel cells: What and Why?
Chemoelectric engine that convert chemical energy of the fuel direct to electricity.
Clean energy:
Hydrogen + Oxygen  H2O + Heat + electricity “Fuel cell vehicle”
Gasoline + Oxygen  CO2 + H2O + Heat + electricity “Gasoline vehicle”
“air pollutant”

5. Fuel cells: What and Why?
High energy density (kWh/kg) :
Energy produced per unit weight of the fuel
High efficiency:
No moving parts
Combined heat and power (CHP) generation
Unlimited runtime:
In fuel cell, no charging time like batteries

6. How Fuel Cell Works

7. Direct Ethylene Glycol Fuel Cell (DEGFC): Advantages
Ethylene glycol is liquid fuel much safer and easier to transport and handle than pressurized H2 cylinders
Large Energy Density & less expensive hydrogen source
HCOOH → CO2 + 2H+ + 2e “DFAFC provide kW.h/kg” FA
CH3OH + H2O → CO2 + 6H+ + 6e “DMFC provide kW.h/kg”
MeOH
CH2OH-CH2OH + 2H2O → 2CO2 + 10H e− “DEGFC provide kW.h/kg” EG

8. Limitation: Poisoning of Pt catalyst
CO poison formation:
Pt-COads
main catalyst poison
CO2 evolution:
Ptfree
Surface Modifier “MOx NPs”
CH2OH-CH2OH + 2H2O CO2 + 10H e− EG
Fig. (A)
Fig. (B)

9. How Nanoparticles solve the problem of catalyst poisoning
(1) Bifunctinal effect:
Provide Oxygen containing species to adsorbed CO generating CO2
(2) Third body effect “ensemble effect”:
Change the geometry required for the adsorption of CO poison on the Pt substrate “i.e.; prevent Pt atoms contiguity”.
(3) Electronic effect:
Change electronic structure of Pt to weaken the binding energy between Pt &CO.

10. Experimental A. Electrodes and pretreatments B. Electrode modification
Chemicals & solutions
Electrochemical measurements Potentiostat
Electrochemical cell
Electrodes
Working electrode: GC
Reference electrode: Ag/AgCl/KCl(sat.)
Counter electrode: spiral Pt wire
B. Electrode modification
nano-Pt & nano-MOx
C. Materials Characterization
Electrode morphology & surface composition
FE-SEM & EDS

11. Characterization of electrodes: Morphological
FE-SEM Pt/GC electrode.
FE-SEM of NiOx/Pt/GC electrode.
FE-SEM of MnOx/Pt/GC electrode.
FE-SEM of CoOx/Pt/GC electrode.

12. Characterization of electrodes: Compositional
EDS of Pt/GC electrode.
EDS of NiOx/Pt/GC electrode.
EDS of MnOx/Pt/GC electrode.
EDS of CoOx/Pt/GC electrode.

13. Characterization of electrodes: Electrochemical
CV of Pt/GC electrode.
CV of NiOx/Pt/GC electrode.
Ni(OH)2 ↔ NiOOH + H+ + e-

14. CoOx/Pt electrode: Characterization
CV of MnOx/Pt/GC electrode.
CV of CoOx/Pt/GC electrode.
2 MnOOH + 2 OH− ↔ 2 MnO2 + 2 H2O + 2 e−
3 Co (OH)2 + 2 OH- → Co3O4+ 4 H2O+ 2 e−
Co(II) Co(II)&Co(IV)
Co3O OH- + H2O → 3 CoOOH + e−
Co(II)&Co(IV) Co(III)
CoOOH + OH- → CoO2 + H2O + e−
Co(III) Co(IV)

15. Ip is 2 times of that obtained at Pt/GC
Electrocatalytic activity of ethylene glycol (EG) oxidation at various electrodes
CoOx/Pt/GC
MnOx/Pt/GC
Highest enhancement
at CoOx/Pt/GC
Ip is 2 times of that obtained at Pt/GC
NiOx/Pt/GC
Pt/GC
LSVs for EGO at a) Pt/GC, b) NiOx/Pt/GC, c) MnOx/Pt/GC and d) CoOx/Pt/GC electrodes in 0.5 M NaOH solutions containing 0.5 M EG. Potential scan rate is 50 mV s−1.

16. Stability of CoOx/Pt/GC electrode
NiOx/Pt
CoOx/Pt/GC Pt
Pt/GC
I-t curve for 3 h of continuous electrolysis.
 Highest activity
 Highest stability

17. Origin of catalysis NiOx MnOx CoOx 2 pathways
Ni(OH)2 ↔ NiOOH + H+ + e-
Ni(II) Ni(III)
MnOx
2 MnOOH + 2 OH− ↔ 2 MnO2 + 2 H2O + 2 e−
Mn(III) Mn(IV)
CoOx pathways
Co(OH)2 + OH- ↔ CoOOH + H2O + e CoOOH + OH- ↔ CoO2 + H2O + e-
Co(II) Co(III) Co(III) Co(IV)
CoOOH + EG → intermediates + Co(OH) CoO2 + EG → intermediates + CoOOH
CoOOH + intermediates → products + Co(OH) CoO2 + intermediates → products + CoOOH

18. Conclusions
1) nano-NiOx, nano-MnOx and nano-CoOx act as catalytic mediators facilitate charge transfer of the EGO better konetis for EGO higher energy obtained from the DEGFC. 2) CoOx/Pt/GC electrode highest catalytic activity towards EGO when compared to Pt/GC, NiOx/Pt/GC and MnOx/Pt/GC electrodes. 3) CoOx/Pt/GC electrode high stability; stable oxidation current over prolonged time of oxidation Role of “nano-CoOx”

20. Origin of catalysis
2 MnOOH + 2 OH− ↔ 2 MnO2 + 2 H2O + 2 e− Mn(III) Mn(IV) 2 MnO2 + Pt−COads + H2O → 2 MnOOH + Ptfree + CO2 Mn(IV) (main poison) Mn(III) Pt−COads + 2 OH − → Ptfree + CO2 + H2O + 2 e−

21. Origin of catalysis
Ni(OH)2 ↔ NiOOH + H+ + e- Ni(II) Ni(III) Ni(III) + EG → intermediates + Ni(II) Ni(III) + intermediates → products + Ni(II) Co(OH)2 + OH- ↔ CoOOH + H2O + e- Co(II) Co(III) CoOOH + EG → intermediates + Co(OH)2 CoOOH + intermediates → products + Co(OH)2 CoOOH + OH- ↔ CoO2 + H2O + e- Co(III) Co(IV) CoO2 + EG → intermediates + CoOOH CoO2 + intermediates → products + CoOOH