1. 59th International Conference on Analytical
Sciences and Spectroscopy(ICASS)
Nakkiran Arulmozhi
Electrochemistry and Electrocatalysis Laboratory
Department of Chemistry
Queen’s University
1

2. Motivation
2
“Electro-oxidation of COchem on 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

3. 3
Improved Laboratory
Advanced
Single
Crystal
Electro-
chemistry
Laboratory
Automated
Bead
Growth
Facility
CCD
Based
Laue
Diffraction
Precision
Surface
Finish
Annealing
Setup
EC Set-up
Electrolyte
100
Disorder

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 Rate Dependence 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 Diameter Optimization
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 energy of FCC structure
γ{111} < γ{100} < γ{110}
Bead Wobbling Controlled Growth

10. 10
Cost Analysis and Conclusion
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)

11. 11
Acklowdegement
& our research group