PERFECTUATION OF NANO-SCALED NON-PLATINUM ELECTROCATALYSTS FOR HE/O

1. Second Regional Symposium on Electrochemistry South-East Europe June 6 to 10, 2010, Belgrade, Serbia PERFECTUATION OF NANO-SCALED NON-PLATINUM ELECTROCATALYSTS FOR HE/O Orce Popovski *, Perica Paunović** and Svetomir Hadži Jordanov** *Military Academy “General Mihailo Apostolski” Skopje, R. of Macedonia **Faculty of Technology and Metallurgy, University „Sts. Cyril and Methodius“, Skopje, R. of Macedonia orcepopovski@yahoo.com

2. The Hydrogen economy concept • Fossil fuels are the most convenient and available energy sources • Unclosed loop of their exploitation makes them environmentally unfriendly and unsustainable source of energy • The combustion products go into the atmosphere, accompanied with other gases and cause serious pollution • On the other side, the enormous consumption rate of fossil fuels contribute to their soon total exhaust. • Modern science is facing a challenge to find out alternative source of energy which can satisfy the global energy needs, but also to be environmentally friendly. • In this context, the hydrogen economy as system of hydrogen production, storage, transportation and conversion in electricity by fuel cellsis very perspective.

3. Environment Solar Energy Oxygen in Oxygen out Photovoltaic Conversion Water in Water out Hydrogen Storage & Transport Electric Power Water electrolysis Electric Power Fuel Cell The Solar Hydrogen Energy Conversion Cycle The ultimate solution for energy production, saving and conversion is the use of renewable energy sources, and particularly Solar Photo-Voltaic Hydrogen Energy Conversion Cycle

4. Reducing the use of noble metals • Increasing catalytic activity the less noble metals – our crucial task Electrode materials for hydrogen evolution • Electrode materials for HE/O are of critical importance in hydrogen economy concept • Their selection is not at all an easy task • The conflict of technical and economical issues is evident: • the best electrocatalysts (Pt, Pd, Ru) –low abundance, • – high cost • the cheaper one (Ni, Co etc.) –chemical unstable • –low activity

5. How to solve this problem? There are two approaches: Physical approach Increasing of the active surface by lowering the grain size of the catalytic phase and supporting materials to nano-scale • highly developed surface • excellent electrical conductivity • optimal micro porosity • adequate water handling capability • good corrosion resistance Chemical approach Development of multicomponent catalysts with catalytic activity comparable with that of Pt • decrease the noble metal mass • increase the activity as a result of inter electronic and/or inter ionic interactions

6. Co-TiO2 Ni-TiO2 CoPt-TiO2 CoRu-TiO2 CoRuPt-TiO2 Vulcan XC-72; MWCNTs; MWCNTs(a) Bi- and multi-component catalysts E-Tek – 20% Pt / 80%Vulcan XC-72 – the most used electrode material The main goal was: production, characterization and modification of platinum and non-platinum hypo-hyper d-electrocatalyst for HE/O Followed multicomponent systems were prepared by sol-gel method and studied: 10%Me + 18%TiO2 + Vulcan XC-72; MWCNTs; MWCNTs(a)

7. Hypo d-phase Metallic phase (hyper d-) TiO2 (anatase) Ni, Co Electroconductive support material Vulcan XC-72 Non-platinum mixed electrocatalysts Improvement – I step 10% Me + 18% TiO2 + Vulcan XC-72

8. Bi-functional role of TiO2 • Catalyst’s support • SMSI effect Polarization curves Aqeuose solution: 3.5 M KOH room temperature

9. XRD analysis 10% Ni + 18% TiO2 + Vulcan XC-72 A - anatase 10% Co + 18% TiO2 + Vulcan XC-72 A - anatase Co amorphous grain size < 2 nm Ni crystalline grain size 1520 nm TiO2 anatase grain size 78 nm

10. FTIR analysis

11. Hypo d-phase Metallic phase (hyper d-) TiO2 (anatase) Ni, Co Electroconductive support material MWCNTs Non-platinum mixed electrocatalysts Improvement – II step 10% Me + 18% TiO2 + MWCNTs

12. Non-platinum hypo-hyper d-electrocatalysts Polarization curves Aqeuose solution: 3.5 M KOH room temperature

13. Metallic phase (hyper d-) Hypo d-phase TiO2 (anatase) Co, Pt Electroconductive support material MWCNTs(a) Cobalt-platinum mixed electrocatalysts Improvement – III step ACTIVATION • Me = Co • Me = CoPt (4:1) • Me = CoPt (1:1) • Me = Pt 28% HNO3  = 4 h t = 25oC 600 rpm 10% Me + 18% TiO2 + MWCNTs (a)

14. To1= 180oC Tp1= 278oC Tp3= 893oC Tp2= 645oC To2= 585oC Non-activated MWCNTs To3= 847oC Activated MWCNTs To1= 173oC Tp1= 272oC Tp2= 757oC Tp2= 575oC To3= 617oC To2= 523oC TGA/DTA Activated MWCNTs higher thermal stability  smaller diameter of tubes, higher level of purity

15. RAMAN spectroscopy Activated MWCNTs higher crystallinity lower amount of amorphous carbon

16. Polarization curves

17. XRD analysis Pt – 11 nm Anatase – 3-4 nm Pt – 4 nm Anatase – 3-4 nm

18. Electrocatalytic activity for hydrogen evolution in the EasyTest Cell ELAT – 0.5 mg.cm-2 Pt + Vulcan XC-72 1 – 10% Co + 18% TiO2 + MWCNTs 2 – 10% CoPt (4:1) + 18% TiO2 + MWCNTs 3 – 10% CoPt (1:1) + 18% TiO2 + MWCNTs

19. CONCLUSIONS 1. Involving TiO2 stable catalyst support increase of intrinsic catalytic activity trough SMSI 2. Involving MWCNTs as catalyst support increase of catalyst’s surface area imrovement of trans- and inter- particle porosity  better dispersion of metallic phase increase of intrinsic activity 3. Activation MWCNTs as catalyst support higher stability of MWCNTs higher purity (lower amount of amorphous carbon) shortening of the MWCNTs length (increase of surface area) 4. Involving Pt in metallic phase high activity of CoPt (with only 20% Pt in metallic phase) the presence of Co reduces Pt particles (23 times) increase of catalytic activity as result of size effect

20. THANKS FOR YOUR ATTENTION