Introduction / Background

TEM Results

Discussion

Conclusions

Acknowledgements

References

EEC-1132648 Summer Research Project:

ELECTROCHEMICAL CAPACITORS C.S.Peterson; M.P.Yeager; W.Du.; X.Teng

The Joan and James Lietzel Center for Science, Technology, Engineering and Math

Education: Research Experience for Teachers in Engineering Program 2012

Topic: METAL OXIDE NANAOSTRUCTURES AS FARADIAC REDOX REACTIONS FOR ENERGY STORAGE APPLICATIONS OPTIONS WITH

POWER AND ENERGY DENSITIES BETWEEN BATTERIES AND CAPACITORS:

Goal: Can a coating of polypyrrole on nanoparticle Mn3O4 metal oxide be prepared by in-situ polymerization to improve the specific capacitance of by reducing charge-transfer resistance over the electrode/electrolyte

interface?

Electrochemical capacitors (EC) store energy in an electric field that can be charged and discharged rapidly. These electrochemical capacitors are useful in combination with conventional batteries in providing electrical energy storage and release where rapid high power delivery or uptake is needed. Though small single cell low voltage EC have been commercially available, different applications require improved energy density.

Psuedo-capacitors or redox-supercapacitors (SCs) are a class of the EC energy storage device that fill the gap between batteries with high energy densities and electrostatic capacitors with high power densities. These redox-capacitors rely on metal oxides nanomaterials which undergo fast and reversible surface reactions for charge storage. Emerging energy applications for EC/SC with characteristics of high power and improved energy densities has prompted research into materials for electrodes in EC/SCs. These materials should be low cost, low toxicity, have large specific capacitance and long life cycle based on to their potential for multi-electron transfer during Faradaic reactions.

This is an investigation to enhance the conductivity of the redox reaction by reducing the distance traveled to between the metal oxide and the electrode through creating a nanometer thickness layer of polypyrrole conductive polymer on the metal oxide through in-situ polymerization.

To facilitate charge transfer of Faradaic redox reaction of : Mn+2--> Mn+3 + e-conductive polymer, polypyrrole, PPy, was formed from the monomer in-situ with nanoparticle metal oxide.

 Compared cyclic voltagrammetric specific capacitance

*100/ % Mn3O4 (+ 20% PTFE non-conductive) *50/50 % in-situ polymerizered pyrrole / Mn3O4 *90/10 % in-situ polymerizered pyrrole / Mn3O4

*100 % polymerizered pyrrole

In-situ polymerization of pyrrole on metal oxide nanoparticles for pseudo capacitors.IN-SITU Polymerization

Synthesis: Nanoparticle Metal Oxide Mn3O4

7/12 syn /50% by weight PPy 1 to 10 Mn3O4to PPy:

7/12 syn with 10% /90% by weight PPy

50/50 % by weight Ppy/Mn3O4:

90/10 % by weight Ppy/Mn3O4

7/12/12 synthesis

The optimization of electrode materials are critical for further development. Increasing the surface area through synthesis of nanometer size particles increase surface reactions. How these metal oxides are adhered to the electrode may play a significant role in their effectiveness. Though there is ongoing research of the choice of metal oxide for redox reaction, reducing the resistivity to the electron charge transfer to the electrode from the Faradaic redox reaction may enhance the specific capacitance and charge / discharge cycle endurance of the psuedo-capacitor.

Cat Peterson is an in-service high school teacher in Naugatuck, CT. Prior to teaching, she earned a B.S. in Chemistry from the University of Connecticut and enjoyed ten years of S.T.E.M. careers, holding jobs as application chemist, quality director, product/ project manager and program launch leader for a variety of engineered polymer composite manufacturers. Cat then became certified in 7-12 grade Chemistry and General Science, and teaches Academic and Honors chemistry to sophomores and juniors along with diverse science electives. After earning her M.S. in Chemistry from Saint Joseph College in 2009, she had been reenergized in promoting S.T.E.M. education and career awareness. This opportunity to conduct summer research in a S.T.E.M. area through the National Science Foundation grant awarded to the James and Joan Lietzel Center at the University of New Hampshire, Durham, NH. has empowered her to encourage, excite and teach students to appreciate science, math, technology and engineering.

The Mn3O4 metal oxide was synthesized per a method devised by Matt P. Yeager et al. The material was centrifuged, vacuum dried and massed to allow for nown ratio of metal oxide to polymer. Verification of particle size of 15-20 nm by TEM magnification 40000 times is shown below:

Prepared dilute solution MnCl210 mL of  DIDW H2O70mg Mn(II)Cl2*4H2O

Prepared 0.300 M KOH:10 mL of DIDW H2O

    163 mg KOH Placed in Syringe Pump

Added dropwise with programmable syringe pump at rate of 0.167 ml per minute for 50 minutes. 145 mg KOH / 8.33 mL used. Allowed 30 additional minutes stirring to react. Used four centrifuge tubes. Centrifuged for 10 minutes: clear supernatant. Decanted and consolidated to two tubes. Filled with DI H2O for wash and centrifuged for 10 minutes. Decanted and consolidated to one tube. Filled with ethanol and centrifuged 10 minutes. Decanted and vacuum dried at room temp for 16 hours. TEM sample prepared on carbon support .

Half Cell Results

Hope to get some actual CVs this week and calculate Specific Capacitance for plain glassy carbon electron and four samples listed above

Report in Farads per gramCompare to other 650 F g-1 etc.

A sample of Mn3O4 from synthesis, mass of 10.2 mg was diluted with 4.450 mL to a 0.010M aqueous solution which was sonicated for 10 minutes prior to and 10 additional minutes after adding 105 L of a 10% pyrrole monomer dissolved in ethanol. To initiate polymerization 105 L of 0.010M aqueous Fe(NO3)3 was added, followed by 30 minutes of sonication. The sample was centrifuged and dried. A small dimension particles appeared to settle. A similar method was used in the preparation of the 9 to 1 sample pyrrole / M3O4, using 9 times the amount of pyrrole and Fe (NO3)3. The particle size that settled was noticeably larger and descended at an increased rate.

50/50 % in-situ polymerizered pyrrole / Mn3O4

90/10 % in-situ polymerizered pyrrole / Mn3O4

TEM images were taken from samples that had been oven dried and then redissolved in ethanol, prepared on carbon supported copper wire screens.

TEM images are at 40000 times magnification.

The 15-20 nm octahedral shape Mn3O4 particles can still be vsualized though the particles appear to be clumped together in 100-300 nm structures, The lighter gray, more evident in the 90/10, is assumed to be the polypyrrole compound.

FURTHER INVESTIGATIONS: •Comparision to other ratios of Ppy/Mn3O4 for optimization or other conductive polymers.•SEM determination of individual particle size Even if the PPy / Mn3O4 are not clearly distinct individually coated particles, the aggregate particle size appears to be less than 1000 nm and have a high surface area structure.

• UNH Department of Chemical Engineering• Xaiowei Teng, Wenxin Du, Matthew P. Yeager for encouraging me to undertake a unique direction utilizing

their resources which allowed me to pursue a distinct research project and enduring my unending questions

• Matthew Sullivan and Dom Montollo for coaching with laboratory synthesis and testing procedures.• Carole Lessard, Katie Stella, Baron Richardson, Michelle Kelly, Berkley Sadona and April Cartwright for

their camaraderie, inspiration, and sharing of their instructional experiences in a professional development mode.

• Nancy Cherim, at UNH-UIC for access, training and assistance in TEM photography.• Stephen R. Hale, at the Lietzel Center for coordinating the RETE program and providing well- defined

direction, appropriate resources, confident leadership and encouragement throughout this experience.

Mass on electrode of 5 micrograms total; therefore Mn3O4 loading was reduced while Ppy was increased