Roles of Carbon Nanostructures for Advanced Energy Solutions Prashant V. Kamat University of Notre Dame Radiation Research Laboratory South Bend, IN Presented by: Brian Ellis, UW

Outline Fuel cells, carbon nanotubes and current research Proposed areas of research Resources

Scope of Research Fuel cells: energy conversion device Applications: portable electronics, home power generators, zero- emission vehicles Utilize carbon nanostructures (fullerenes, carbon nanotubes etc) as support to boost the electrode performance Design of new metal catalysts and composites for improving the efficiency of electrode reactions Develop membrane assembly and evaluate the overall performance in portable fuel cells (Direct methanol and hydrogen fuel cells) GM Hy-wire GM HydroGen3

Fuel Cells Anode 2 H 2 4 H e - CH 3 OH CO + 4 H e - Cathode O 2 (g) + 4 H e - 2 H 2 O Both reactions require catalyst (Pt or Pt alloy)

Properties of SWNT’s Conductivity: metallic when fully aromatic Strength: resistant to bending, stretching Surface area: m 2 /g Porosity: hollow Functionalization: can perform many reactions with nanotube surface to add reactive groups, pendant molecules, polymers P. M. Tajayan. Chem. Rev. 99 (1999), D. Tasis et. al. Chem. Rev. 106 (2006), 1105.

Nanotube Applications for Fuel Cells Carbon nanostructures: high surface area, mechanical strength, conductivity Candidate materials for hydrogen storage Electrode surfaces: minimize use of precious metals Maximize electrode area (porous supports for catalysts)

Recent Research in the Kamat Group

Deposition of SWNT films One-step solubilization of SWNT: sonicate SWNT with tetraoctylammonium bromide, prevents aggregation Film deposition: conducting glass plate (doped tin oxide) dipped in organo-silane to functionalize surface Electrodeposition (50V DC) CNT in THF CNT in THF/TOAB CNT film P. V. Kamat et. al. J. Am. Chem. Soc. 126 (2004),

Alignment of Nanotubes in a DC Field Apply high DC voltage (>100V): polarization of nanotubes Linear bundles form, aligned perpendicular to electrode surface P. V. Kamat et. al. J. Am. Chem. Soc. 126 (2004),

Pt Deposition on SWNT films CNT film immersed in solution of H 4 PtCl 6 Electrochemical pulses (12ms) at -350mV vs. SCE until 0.1 C reached Loading: 56μg/cm 2 of Pt Pt nanoparticles: uniform size, 20nm diameter P. V. Kamat et. al. J. Phys. Chem. B. 108 (2004),

Pt on Fullerenes C 60 suspension in acetonitrile Conducting glass electrodes, electrodeposition (100V DC) produces brownish film Loading of Pt: fullerene film immersed in solution of H 4 PtCl 6, electrodeposition at -350mV vs. SCE Pt: nm clusters P. V. Kamat et. al., Nano Lett., 4 (2004), 415.

TiO 2 -Pt/Ru Hybrid Electrodes Large band gap semiconductors (TiO 2 ) photocatalyze methanol oxidation; supplement Pt/Ru catalyst system Prepared Pt-Ru catalyst brushed onto one side of carbon fiber paper; TiO 2 suspension dropped onto other side Anode Pt/Ru TiO 2 C-paper TiO 2 on C-paper Pt/Ru on C-paper P. V. Kamat et al. J. Phys. Chem. B. 109 (2005),

Proposed Topics of Research

Mesoporous Carbon Deposition of carbon onto mesoporous silica 1) Sodium silicate + CTAB + non-ionic surfactant Mesoporous SiO 2 2) Mesoporous SiO 2 + sucrose + H 2 SO 4 C/SiO 2 3) C/SiO 2 + NaOHMesoporous C High Surface area ( m 2 /g) Electrodeposit Pt nanoparticles onto C B. Fang et. al. J. Pyhs. Chem. B. 110 (2006), 4875.

Metal Core-Pt shell Nanoparticles Any inexpensive metal/metal oxide could be used as core (Ni, Co, Fe, Fe 3 O 4, etc) Ni core: NiCl 2 + CTAB + N 2 H 4 H 2 ONi nanoparticles Ni core/Pt shell nanoparticles: Ni nanoparticles + H 2 PtCl 6 + potassium bitartarate Disperse with nanotubes in sonicator, microwave heating to fuse nanoparticles to nanotubes Pt Ni Cushing et al. Chem. Rev. 104 (2004), 3893.

Funtionalize SWNT’s deposited on electrode: Add bis-(ethylenediamine)platinum (II) chloride: Nucleophilic substitution Monolayer Pt Surface on SWNT’s °C, F 2 [(H 2 NCH 2 CH 2 NH 2 )Pt]Cl 2 NH NH 2 NH NH 2 NH NH 2 NH Cl-Pt-Cl D. Tasis et. al. Chem. Rev. 106 (2006), 1105.

Monolayer Pt Surface on SWNT’s H 2 PtCl 6 electrodeposition NH NH 2 NH NH 2 NH NH 2 NH Cl-Pt-Cl H 2, 400°C Pt Reduce Pt 2+ to Pt, deposit on surface

Aligned SWNTs Increase the concentration of nanotubes to cover electrode

Aligned SWNTs: Hydrogen Storage Dissolve electrode in acid, network of aligned SWNT’s remains Potential material for hydrogen storage H2H2 Exact mechanism and sites for absorption not known

Purchases Brunauer, Emmett, Teller (BET) surface area equipment ($50,000) Raman spectrometer for characterizing CNT’s ($180,000)

Conclusions Carbon nanostructures have physical properties (high conductivity, strength, porosity) applicable for use in fuel cells Utilize these materials for increasing the surface area of electrodes and hydrogen storage Deposit Pt nanoparticles or mixed core-shell nanoparticles to minimize the amount of precious metals consumed

Acknowledgements Collaborators K. Vinodgopal, Indiana University Northwest D. Meisel, Notre Dame Radiation Laboratory Students/Postdocs S. Barazouk, K. Drew, G. Girishkumar, I. Robel