Porous silicon as base material of MEMS-compatible fuel cell components José Geraldo Alves Brito Neto Tokyo University of Science - Faculty of Science and Technology Department of Mechanical Engineering - Hayase Group
Cathode Anode Galvanic Cells
Galvanic Cells Load Cathode Anode Salt Bridge
Anions Electrons Anode Side Reduced Reagent Cations Oxydized Product
Electrons Load Salt Bridge Cations Cathode Anode Anions
Cations Electrons Cathode side Anions Reduced Product Oxidized Reagent
Galvanic Cells Load Current Cathode Anode Salt Bridge
Galvanic Cells Current Load Anode Cathode
Galvanic Cells Current Load Ri Anode Cathode
Fuel Cells Electron donor: Fuel (H2, methanol, ethanol, glucose??) Electron acceptor: O2 Salt bridge: aqueous alkaline solution, molten alkaline carbonate, O2- conducting ceramic, polymeric electrolyte
Polymer Electrolyte Membrane Fuel Cells
Polymer Electrolyte Membrane Fuel Cells Nafion
Polymer Electrolyte Membrane Fuel Cells
Polymer Electrolyte Membrane Fuel Cells
Polymer Electrolyte Membrane Fuel Cells Current collector/ Field flow plates
Polymer Electrolyte Membrane Fuel Cells Gas diffusion layer
Polymer Electrolyte Membrane Fuel Cells Oxidation Catalyst Layer
Polymer Electrolyte Membrane Fuel Cells Anode
Polymer Electrolyte Membrane Fuel Cells Cathode Current collector Gas diffusion layer Reduction catalyst layer
Polymer Electrolyte Membrane Fuel Cells Polymer Electrolyte Membrane
Polymer Electrolyte Membrane Fuel Cells
Polymer Electrolyte Membrane Fuel Cells H2 O2
Current Collector Gas Diffusion Layer H2 Catalyst Layer Polymer Electrolyte Membrane H2 Electrons H+
Electrons Load H2 O2
Polymer Electrolyte Membrane Catalyst Layer Gas Diffusion Layer Current Collector H2O H+ O2 O2 Electrons
Polymer Electrolyte Membrane Fuel Cells Typically employed materials: Gas diffusion layer: carbon cloth Catalyst layer: platinum nanoparticles supported on finely divided carbon black Polymer electrolyte membrane: Nafion
source: Li et al - Electrochimica Acta 2006 51 5250
2 He (...) 5 6 7 8 9 10 B C N O F Ne 13 14 15 16 17 18 Al Si P S Cl Ar 29 30 31 32 33 34 35 36 Cu Zn Ga Ge As Se Br Kr (...)
2 He (...) 5 6 7 8 9 10 B C N O F Ne 13 14 15 16 17 18 Al Si P S Cl Ar 29 30 31 32 33 34 35 36 Cu Zn Ga Ge As Se Br Kr (...)
We must synthesize and manipulate porous materials by MEMS-compatible methods
We must synthesize and manipulate porous materials by MEMS-compatible methods Porous Silicon
Porous Silicon Silicon Wafer Counter electrode HF-containing bath
Porous Silicon Facile synthesis Compatible to MEMS technologies Wide range of pore morphologies can be obtained by changing simple parameters.
Porous Silicon Porous layer 5 m Bulk silicon
Porous Silicon
Porous Silicon Porous layer Bulk silicon 500nm
Porous Silicon
Immersion plating By immersion of the porous silicon sample in a solution containing PtCl62ions and HF, the following reactions take place: PtCl62-(aq) + Si(s) + 2H2O - SiO2(s) + 6F (aq) + 4H+(aq) - Pt(s) + SiO2(s) + 4H+(aq) + 6Cl (aq) SiF62-(aq) + 2H2O
Porous layer 5 m Bulk silicon
Porous platinum!! Porous layer Bulk silicon 5 m
138 Pt M line 810 Si K line 5 m Porous layer Bulk Silicon 5 m 0 0
Porous Platinum Roughness factors on the order of 600; Area/volume rations on the order of 80 m2/cm3
Cell assembly Silicon wafer Oxide layer
Cell assembly Removal of oxide layers by dipping in concentrated HF
Cell assembly Sputtering of a Cu layer
Cell assembly Patterned dissolution of the Cu layer
Cell assembly Formation of a porous silicon layer on the opposite face
Cell assembly Immersion plating of the Pt catalyst
Cell assembly Deposition of Ti and Au contact bands
Cell assembly Plasma etching of the fuel channels
Cell assembly Anode Cathode
Cell assembly Anode Polymer Electrolyte Membrane Cathode
Cell assembly Hot pressing of the membrane-electrode assembly Anode Polymer Electrolyte Membrane Cathode
Electrons H2 A Load Anode Cathode O2
Next Steps Extend the synthetic method to other metals Improve the characteristics of the porous Pt layers Solve problems of the cell assembly procedure Develop methods to produce other components of the cell based on porous silicon