1 welcome allison mentor: dr. tratnyek frontline mentor: jim nurmi
TRANSCRIPT
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1WELCOME
Allison Mentor: Dr. Tratnyek
Frontline Mentor: Jim Nurmi
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• Manganese Metal (Mn0)– Atomic Number 25– Second most abundant
transition metal in the Earth’s crust.
– Physical and chemical properties similar to iron metal.
• Aq Manganese (Mn2+)– Bioavailable form of
manganese.– Found in soils, sediments,
and natural waters.– Occurs as a cation in
solution.
Reduced Forms of Manganese
http://en.wikipedia.org/wiki/Manganese
Photo from Wendy Smythe
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• Manganese Dioxide (MnO2)– Plays a key role in the
biogeochemical cycles of metals and organic carbon.
– Can degrade pollutants through oxidation.
– Used as a cathode in dry cells and batteries.
• Permanganate (MnO4-)
– Powerful oxidizer used for water treatment.
– Violet color
Oxidized Forms of Manganese
www.liboxgoa.com/potassium%20permanganate.html
http://en.wikipedia.org/wiki/Manganese_dioxide
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4Areas of Manganese Research
• Accumulate charges at the electrode/electrolyte interface.
• Power supply
• Naturally abundant• Bacteria can oxidize Mn(II) in natural
aqueous environments
• Environmental impact• Overexposure can lead to permanent,
neurodegenerative damage, with symptoms of Parkinson’s disease
• Soil and sediment remediation • Metal removal and recovery
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5Purpose: Capacitance of Biogenic Manganese
Compare the electrical potential of synthetic MnO2 and biogenic manganese oxides by fabricating electrodes and measuring current vs. potential by cyclic voltammetry.
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6Electrochemical Setup
• Potentiostat • Glassy carbon rotating
disk electrode • Ag/AgCl reference
electrode• Platinum wire counter
electrode• Na2SO4 electrolyte
solution
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• Self Made– Precipitate KMnO4 and polyethelyne glycol
• Adapted from Ragupathy, P., et al, “Remarkable Capacity Retention of Nanostructured Manganese Oxide upon Cycling as an Electrode Material for Supercapacitor”
• Manufactured– Mn2O3 from Fisher Scientific
• Biogenic manganese from P. Putida GB-1
Source of Materials
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• Ethanol• 5 wt % Nafion solution
• MnO2 particles
Comparison of Methods: Mao’s Method
iAdapted Mao, L., et al. “Electrochemical Characterization of Catalytic Activities of Manganese Oxides to Oxygen Reduction in Alkaline Aqueous Solution.” Journal of The Electrochemical Society, 149 (2002): 504-507.
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9Comparison of Methods: Liu’s Method
• MnO2
• Acetylene black
iiAdapted from Liu, E., et al. “Potentiodynamical deposition of nanosized manganese oxides as high capacitance electrochemical capacitors.” Journal of Materials Science: Materials in Electronics 18 (2007): 1179–1182.
• Polyvinylidene fluoride (PVDF)
• N-methyl-2-pyrrolidone (NMP)
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10Method Experimentation Results
•Liu’s Method is used in because of better electrode coverage
•Electrode tip must be heated in so MnO2
slurry adheres to electrode
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11Results
Fig. 1aCyclic voltammetry,Various types of manganese on electrode surface
Fig. 1bDifferential CV,ΔI vs. Potential Manganese
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12Conclusions
• Reproducible electrochemical results • CVs of synthetic manganese oxides and
biogenic manganese produce different results, which demonstrates that they have different electrochemical characteristics.
• Larger capacitance differences are observed at intermediate potentials
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Thank you Dr. Paul Tratnyek, Dr. Jim Nurmi, Karen Wenger, Dr. Antonio Baptista, Elizabeth Woody, CMOP, and the Apprenticeships in Science and Engineering program for making my internship possible.