1. Solar Hydrogen Project Group Update 29 th July 2009

2. Ir Deposition Growth Nucleation

3. Week 4 Progress Zack Ulissi

4. Mesh Cathode (Conductor) Membrane Photo-Anode Absorption, αe-e- h+h+ 2e 2H + H2H2 + Diffusion Kinetics Fluid Flow+ Diffusion Fluid Flow+ Diffusion H2OH2O + 2H + O2O2 Kinetics Absorption, Diffusion (2), Band Bending Electrolyte Flow (if laminar)

5. Tertiary Current Distribution pH Distribution Gradient Driven Convection Plate Voltage Potential Distribution in Reactor Electrochemica l Reaction Rates Band Bending Electrolyte Distribution

6. Tertiary Current Distribution pH Distribution Gradient Driven Convection Plate Voltage Potential Distribution in Reactor Electrochemica l Reaction Rates Band Bending Electrolyte Distribution

7. pH Distribution Plate Voltage Potential Distribution in Reactor Electrochemic al Reaction Rates Band Bending Electrolyte Distribution Assume a strong supporting electrolyte Assume no band bending (for now) Permittivity based on electrolyte concentration Voltage Distribution

8. pH Distribution Plate Voltage Potential Distribution in Reactor Electrochemic al Reaction Rates Band Bending Electrolyte Distribution Diffusion Term Force from electrical pot. Reaction Term Convection term (from flow) Coupling H + and OH - : pH=6 V=0V, pH=5.3 V=0.1V, pH=6.8

9. pH Distribution Plate Voltage Potential Distribution in Reactor Electrochemic al Reaction Rates Band Bending Electrolyte Distribution pH=6 V=0V, pH=4 V=0.1V, pH=6.8 OH- Consumption Reaction (O2 Production) Next: Buttler-Volmer kinetics based on potential and H + /OH - concentrations

10. Fluid flow in the bioreactor

11. FZ update Testing Clarks electrode (pO2 probe) for measuring dissolved H 2 Update on sartorius reactor fittings/ tubing

12. Clark-type electrode: (A) Pt- (B) Ag/AgCl-electrode (C) KCl electrolyte (D) Teflon membrane (E) rubber ring (F) voltage supply (G) galvanometer The Clark Electrode is an electrode that measures oxygen on a catalytic Pt surface using net reaction: O 2 + 4 e − + 2 H 2 O → 4 OH −

13. Anode (Pt) Cathode (Pt) Reference Ag/AgCl Guard (Pt) Polarization voltage -670 +/- 50 mV Sartorius/ Hamilton Dissoved oxygen sensor