== Graphene Micro-Supercapacitors ==
Co-I [[GarrettFrankson]] and [[AustinJeffries]]
<<BR>>
Current Status: Building Project Page
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=== Project Overview ===
The electronic devices we use in our everyday life utilize two different types of electrical sources in order to operate: batteries and capacitors. A battery stores a fair amount of energy but is slow to charge and discharge (low power density). A capacitor can charge and discharge very rapidly (high power density) but stores a very small amount of energy. A supercapacitor combines the best of both by storing a large amount of energy while also being able to charge and discharge very rapidly.
A capacitor is often constructed with two layers of conducting foil separated by a paper-thin layer of insulator. The capacity of such a device is proportional to the area of the foil A and inversely proportional to the insulator thickness t, C∝A/t. A supercapacitor has an atomic scale insulator thickness given by the solvation layer surrounding an ion in an electrolyte, and a large surface area. Supercapacitors on the order of 10^0^ - 10^3^ Farads are now [[https://www.sparkfun.com/products/746|commercially available]] and approach the energy density of batteries while still offering fast charge and discharge rates.
The authors of the ''Nature'' paper below, El-Kady and Kaner, have provided a [[http://vimeo.com/51873011|video introduction]] to graphene based supercapacitors.
{{http://i.imgur.com/fJd0bZS.jpg|Fabrication of Microsupercapacitors|width=1000}}
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=== Project Goals ===
===== Short Term Goals =====
1. Create graphene micro-supercapacitor material using the methods outlined by El-Kady and Kaner.
2. Conduct a series of tests on how to maximize the amount of charge stored within each graphene micro-supercapacitor.
===== Long Term Goals =====
1. Design an apparatus that can hold many graphene micro-supercapcitors in an efficient and usable way for use in application.
2. Experiment with powering small mobile devices (ie. a flash light, a watch, a cellphone).
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=== Relevant Publications ===
[[http://www.nature.com/ncomms/journal/v4/n2/pdf/ncomms2446.pdf|Scalable fabrication of high-power graphene micro-supercapacitors for flexible and on-chip energy storage]]
*Maher F. El-Kady & Richard B. Kaner
*El-Kady and Kaner demonstrate a scalable fabrication of graphene micro-supercapacitors over large areas by direct laser writing on graphite oxide films. More than 100 micro-supercapacitors can be produced on a single disc in 30 min or less. The devices are built on flexible substrates for flexible electronics and on-chip uses. Remarkably, miniaturizing the devices to the microscale results in enhanced charge-storage capacity and rate capability. These microsupercapacitors demonstrate a power density of ~200 W cm^-3^, which is among the highest values achieved for any supercapacitor.
[[http://pubs.acs.org.ezproxy.library.wisc.edu/doi/pdf/10.1021/ja01539a017|Preparation of Graphitic Oxide]]
*William S. Hummers & Richard E. Offema
*The conventional method for the preparation of graphitic oxide is time consuming and hazardous. Hummers and Offema have developed a rapid, relatively safe [[http://bit.ly/1anuXVF|method for preparing graphitic oxide]] from graphite in what is essentially an anhydrous mixture of sulfuric acid, sodium nitrate and potassium permanganate.
[[http://research.chem.psu.edu/mallouk/articles/cm981085u.pdf|Layer-by-Layer Assembly of Ultrathin Composite Films from Micron-Sized Graphite Oxide Sheets and Polycations]]
*Nina I. Kovtyukhova et al.
*For the synthesis of graphitic oxide, El-Kady and Kaner used a modified Hummers' method developed by Nina I. Kovtyukhova et al.
*Science 2 August 2013:Vol. 341 no. 6145 pp. 534-537,DOI: 10.1126/science.1239089, Liquid-Mediated Dense Integration of Graphene Materials for Compact Capacitive Energy Storage
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=== Related literature ===
This article
"High-rate electrochemical energy storage through Li+ intercalation pseudocapacitance," http://dx.doi.org/10.1038/nmat3601, http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat3601.html
got me wondering about an old amazing thing. Palladium is a sponge for hydrogen, a phenomenon once touted as a means to achieve "cold fusion."
"Hydrogen in thin Pd-based layers deposited on reticulated vitreous carbon—A new system for electrochemical capacitors,"M. Łukaszewskia,
A. Żurowskia,cA. Czerwińskia, Journal of Power Sources Volume 185, Issue 2, 1 December 2008, Pages 1598–1604, http://dx.doi.org.ezproxy.library.wisc.edu/10.1016/j.jpowsour.2008.08.002
http://arstechnica.com/science/2013/08/simple-technique-puts-graphene-capacitors-on-par-with-lead-acid-battery/
-duncan
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=== Finance ===
[[http://bit.ly/10ERnrN|Short term budget]]
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=== Material Safety Data Sheets ===
[[https://dl.dropboxusercontent.com/s/jlb2lp4a8j9ed6f/msds_NaNO3.pdf?token_hash=AAGDr00itM6VIIO58fTmJvg9dXfPPMU9MCdDNeYyvee3PQ&disable_range=1|Sodium Nitrate]]
[[https://dl.dropboxusercontent.com/s/lvmatpsqzzhpqzh/msds_P2O5.pdf?token_hash=AAEEvlmiLbqMVwHMnd9RgIEdSnAUcjztoVQPY5pHef8QsQ&disable_range=1|Phosphorus Pentoxide]]
[[https://dl.dropboxusercontent.com/s/lx2807zy39s0kwk/msds_KMnO4.pdf?token_hash=AAGeQOzIkfuJUVHJxj_xQEdRLh3Tt1a-2H5bmvxrQ-LQ5Q&disable_range=1|Potassium Permanganate]]
[[https://dl.dropboxusercontent.com/s/2m89qe5jti1yq02/msds_H2SO4.pdf?token_hash=AAEMa6XIVAg8n60fH4t3fxZe8loLCagE_p4DmND7wOFgBg&disable_range=1|Sulfuric Acid]]
[[https://dl.dropboxusercontent.com/s/3mi2rcfctc1y0sk/msds_H2O2_3%25.pdf?token_hash=AAFOVWNSiH2XxhBTp7OqdkucaIEe5dqbHpPGd4waFy_K6g&disable_range=1|Hydrogen Peroxide]]
[[https://dl.dropboxusercontent.com/s/uro3qybz6zyh25v/msds_Graphite.pdf?token_hash=AAHPU8pcn7vEmAcjJDCu9vtf_p-3gh0bUFFvIHbtzuMh2w&disable_range=1|Graphite]]
[[https://dl.dropboxusercontent.com/s/acc7o4uc6b3k3pu/msds_GrapheneOxide.pdf?token_hash=AAHrhS7oxXmd5odPwaZ0rg1g_0aSdMsm3zTMeY3jR6Ambw&disable_range=1|Graphene Oxide]]
[[https://dl.dropboxusercontent.com/s/6fynh2dafjp76os/msds_GrapheneOxide_inH2O.pdf?token_hash=AAHZ3eg1jHQhpCK0P6ZeSY_7bASWPalDPbe2sDvNTf_8OA&disable_range=1|Dispersed Graphene Oxide]]