An Optimal Design of Electrode Surface Morphology to Improve Water Electrolysis Efficiency
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1) The document proposes a novel "mushroom top" electrode surface morphology to improve the efficiency of water electrolysis through increasing the effective surface area of the electrode. 2) Simulation results show the mushroom structure provides up to a 13.4% increase in surface area compared to other structures like pyramids or straight sidewalls. 3) Experimental testing of nickel electrodes with the mushroom morphology show a linear approximation of a 20.4% reduction in resistance, translating to a 25.6% increase in electrolysis efficiency.
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An Optimal Design of Electrode Surface Morphology to Improve Water Electrolysis Efficiency
- 1. A Novel Design of Electrode Surface Morphology to Improve Water Electrolysis Efficiency Jaehyeong Lee Sangmin Lee, Myra Halpin North Carolina School of Science and Mathematics
- 2. Introduction Fuel economy still hydrocarbon dominant Air, water, and soil pollution Unsustainable Alternatives Electrolysis Has the potential to be cost competitive against hydrocarbon fuels, sustainable (Its just water!) Two ways to improve, use different metal to improve catalytic effect Or increase effective surface area of the electrode
- 3. Surface Area Calculation: Aspect Ratio or Height? Equation to find effective surface area: *d = side length of structure *a = space between structures *h = thickness Constant Aspect Ratio Model Peaks Nanoparticle Surfaces Constant Thickness Model Increases exponentially Smaller d/a
- 4. The Mushroom Top Concept (Left) Pyramid Structure, Additional Surface Area: A-B (Center) Mushroom Structure, Additional Surface Area: A+B (Right) Straight Sidewall, Additional Surface Area: A Effective surface area difference between mushroom structure and straight sidewall structure Shows as much as 13.4% increase in surface area in additional surface area vs. aspect ratio graph
- 5. Electroplating Electroplating selected Ease of control Applied current Plating time Low operating temperature Wide market available Plate thickness directly proportional to plating time and applied current
- 6. Photoresist Patterning/Developing AZ2070 Photoresist, 9um thick: 2000rpm for 30 second spin 1 min, 100属C bake Developing Procedure 400nm UV Exposure 2.5 minutes 150属C Heat Treatment 1.5 minutes MIF300 developing 1.5 minutes
- 7. Butler Volmer Equation Butler Volmer Equation with Ohmic Component 1 0 log(Ja)( A/cm2) -1 Fit of Voltammogram using -2 above Butler Volmer Equation -3 Ohmic fit data-0.5M Buttler Volmer fit -4 0 1 2 3 4 5 6 7 8 E-E0 (V)
- 8. Modifications to Butler Volmer
- 9. Optimal KOH Concentration Different KOH concentrations tested in Pt-Pt system 0.5M, 1.0M, 1.5M, 2.0M Cyclic Voltammetry Analysis using modified Butler Volmer Equation Resistance values compared versus concentrations Between 0.5M and 1.0M, large resistance drop Tapers off past 1.0M, 1.0M selected
- 10. Electrode Mounting Fixture *Kelvin Probe Method used to remove voltage drop through the wire.
- 11. Surface Area Dependence on I-V Characteristics
- 12. Impact of New Surface Morphology on System
- 13. Conclusion The new surface morphology shows significant improvement compared to smooth surfaces SEM photos verify new structures mushroom sidewall gives 4 times more effective surface area than straight side wall Linear approximation: Average Resistance Reduction from approximation 20.4% Translates into 25.6% increase in efficiency.
- 14. Questions?
- 15. Future Works Find trend of electrolysis efficiency as function of pattern size and spacing Photolithography techniques with higher controllability Smaller pattern size Further increased effective surface area Apply mushroom top surface morphology with high aspect ratio materials (nanowires/nanotubes) Other nonnoble metals with greater catalytic effect than Ni Cobalt/Manganese High efficiency electrolysis may become a prominent source of fuel in the future.