CATALYZING HYDROGEN PRODUCTION FROM NABH4 USING BIMETALLIC FE@CO NANOPARTICLES
1. CATALYZING HYDROGEN
PRODUCTION FROM NABH4
USING BIMETALLICS &
METHYL VIOLOGEN
Zachary Quinn, Dr. Stacia Rodenbusch,
Nanomaterials for Chemical Catalysis,
University Of Texas At Austin
2. AIM
• Synthesize an optimal metal combination and ratio. For production
of H2 gas from NaBH4
• Have catalytic ability close to palladium at the least
• Stable in air = invulnerable to oxidation
• Synthesized Fe6@Co32 ratio. More ratios possible
• MV and possibly P-NP (clear colored)
3. BACKGROUND I: MV and bimetallics
• Reduction of methyl viologen is quite
easy
• It also turns a bright blue when reduced
from MV2+ to MV+ = indicator
• Bimetallics allow for custom composition
of nanoparticles
• They can have synergistic effects, where
the combination is higher catalytic
activity than either of the metals alone.
Pozun et al. ACS J. Phys. Chem. 2013
Stargardt & Hawkridge. Analytica Chimica Acta. 1983
4. BACKGROUND II: Comp.
• Computational created theoretical
energy maps
• Show binding/segregation energy
for hydrogen and oxygen +
cohesive energy of nanoparticles
• At different ratios with many
metals
• I chose Fe@Co, because its
binding energy was very close to
Pd@Pd: -0.6463 vs. -0.6412 eV
Henkelman/Computational stream.
http://fri.cnm.utexas.edu/~fri/fridb/server.py
5. EXPERIMENTAL PLAN: Monometallics
Co55
DENs
• 31.1 μL G6-OH in 9.939 mL H2O (pH 5*) = 5 μM
• + 27.5 μL CoCl2. Complexed for one hour. + 137.5 μL
NaBH4
Fe55
DENs
• 31.1 μL G6-OH in 9.939 mL H2O (pH 7) = 5 μM
• + 27.5 μL FeCl3. Complexed for one hour. + 137.5 μL
NaBH4
Pd55
DENs
• 8.78 μL G4-OH in 9.939 mL H2O (pH 3) = 5 μM
• + 27.5 μL K2PdCl4. Complexed for 45 minutes + 137.5
μL NaBH4
*Marvin, K. et al. Chem. Comm. (Camb). 2012
6. EXPERIMENTAL PLAN: Fe6@Co32 synthesis/kinetics
●10μM dendrimer: 17.56 μL
G4-OH + 10 mL H2O
● Adjust to pH 5/7
● Add 6 μL of 0.1 M FeCl3
+ 32 μL of 0.1 M CoCl2
●Purge for at least 10 minutes
with Ar gas
●Allow to nutate for 1 hour
● Spec analysis of dendimer
complex
● Add 190 μL of NaBH4 in
H2O/ NaOH (fast/slow)
● Perform kinetic trials:
2 mL H2O, 2 μL MV, 0.1 mL
DEN… 2 μL NaBH4 (H2O)
*In purged quartz cell with
purged reactants
● Analyze every 1 second for
200 seconds
● Wavelength analysis at 257,
400, and 605 nm
9. DATA III: Fe/Co kinetic trials
Fe55 DEN kinetics Co55 DEN kinetics
10. DATA IV: Fe6@Co32 DEN synthesis (pH sensitivity)
1. pH 5- Cobalt DEN synthesis
2. pH 7- Fe DEN synthesis
pH 7 gave higher absorbances with same spec
No mixing or nutating between metal salt additions
1
2
11. DATA V: Fe6@Co32 Reduction paths
Stability
1. Fast reduction– 0.2 NaBH4 in H2O
2. Slow reduction– 0.2 NaBH4 in NaOH
*Specs taken 3 days apart (all purged)
-From stock solution and mixed between
metal additions (peaks).
1
2
12. Gradual change in DEN solutions
3 days
Would agglomerate a few days after reduction. Once occurred
immediately after reduction (bad complex?)
13. 1. Fast reduction– 0.2 NaBH4 in H2O
2. Slow reduction– 0.2 NaBH4 in NaOH
*3 days in unsealed EPI tubes on nutator
DATA VI: Fe6@Co32 Reduction paths
Air exposure for 3 days
1
2
14. DATA VII: Fe6@Co32
Further syntheses– only fast reduction
1. Dendrimer complexes from different days:
missing factor on 11-22 (mixing?)
2. DENs from 11-22. No double
peak like initial DEN spectra.
1
2
16. Trial 1Trial 2
DATA VIII: Fe6@Co32
Kinetics: Round 2
Trial 1: 0.00004 AU sec-1 Trial 2: 0.00004 AU sec-1
*These values should not be positive, should decrease in 257 nm absorbance
17. CONCLUSIONS & FUTURE DIRECTIONS
• Monometallics were unstable and were poor catalysts
• Fe6@Co32 nanoparticles are much more stable over time
• Somewhat stable when exposed to air
• Spectrum shape and decrease in absorbance
• They seem to have little catalytic ability:
• Perhaps due to poor DEN synthesis
• Further trials will be redone to attain spectra similar to
initial trials.
