1WELCOME

Allison Mentor: Dr. Tratnyek

Frontline Mentor: Jim Nurmi

2

• 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

3

• 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

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

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.

6Electrochemical Setup

• Potentiostat • Glassy carbon rotating

disk electrode • Ag/AgCl reference

electrode• Platinum wire counter

electrode• Na2SO4 electrolyte

solution

7

• 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

8

• 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.

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)

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

11Results

Fig. 1aCyclic voltammetry,Various types of manganese on electrode surface

Fig. 1bDifferential CV,ΔI vs. Potential Manganese

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

13

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.