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Towards an Improved Bead Single Crystal Electrochemistry And Electrocatalysis Laboratory
This document summarizes work done to develop an improved automated bead growth facility for growing platinum nanocrystal surfaces. It describes the motivation to study heterogeneous electrocatalyst surfaces at the nanoscale. An automated bead growth system was developed that allows for precise temperature gradients and crystal growth rates through optimized flame conditions and growth parameters. This allows for controlled faceted crystal growth and characterization of platinum nanosurfaces. The new system provides a low-cost alternative to commercial platinum single crystals for fundamental surface science studies.
Towards an Improved Bead Single Crystal Electrochemistry And Electrocatalysis Laboratory
- 1. 59th International Conferenceon Analytical Sciences and Spectroscopy(ICASS) Nakkiran Arulmozhi Electrochemistry and Electrocatalysis Laboratory Department of Chemistry Queen’s University 1
- 2. Motivation 2 “Electro-oxidation of COchemon Pt Nanosurfaces: Solution of the Peak Multiplicity Puzzle” - Langmuir, 2012, 28 (7), pp 3658–3663 Electrocatalyst crystal surface is heterogeneous in nature Structure-reactivity relationship is key factor Rational solution – studies on well defined structure Oxide growth and Electrodissolution studies Need for improved single crystal lab
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- 4. Bead Crystal Growth–Principle Melt Growth - Basis Kinetics Effect Solidification = nucleation + growth Temperature G GSolid GLiquid Tm Solid Liquid Ts ΔT ΔG Driving force for Crystal GrowthThe driving force of Solidification m m a SolidLiq a T TT HG )( Thermodynamics ΔT in small steps → uniform nucleation ΔT in large step → non uniform nucleation Solid
- 5. 5 Bead Growth System– Process and Advantage Temperature Gradient in Flame Process Parameter Flow Rate Mixing Ratio Speed of flame movement S/L boundary movement Controlled (slow) S/L boundary movement Precise temperature gradient (ΔT ) Requirement
- 6. 6 Bead Growth System– Improved Design Set-Up Advantage • Fully automated • Min step size (sub micron) • Min speed (0.9 micron/sec) • Precise flow rate and mixing ratio control • Completely stable and safe
- 7. 7 Flame Optimization Flow RateDependence Mixing Ratio Dependence Why Optimization ? 0.6 0.8 1.0 1.2 1.4 6 8 10 12 14 16 18 20 Length of Flame Fit FlameHeight(cm) Flow Rate (L/min) 40 50 60 70 80 90 100 5 10 15 20 Hydrogen Volume % in Mixture FlameHeight(cm) 2000 2500 3000 TheoriticalMaxFlameTemperature(K) Bead wobble Low temp Distribution
- 8. 8 Growth Optimization Bead DiameterOptimization Weight of the molten drop vs max diameter rgR 2 3 4 3 max R- radius of bead : r – radius of wire µ - mass :σ – surface tension Zone Refining Cycle Optimization After 20 Cycle ̴ 20 Cycles Initial Cycle – 0.0125 mm/s Final Cycle – 0.1 mm/s
- 9. 9 Video Faceted Growth Surface energyof FCC structure γ{111} < γ{100} < γ{110} Bead Wobbling Controlled Growth
- 10. 10 Cost Analysis andConclusion Commercial Pt single crystal – more than 1500$ Quick and complete Safe Physical Understanding Process Parameter Optimization No skill requirement (fully automated) Highly consistent and efficient (optimized process parameter)
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