為了滿足日益增加的能源需求並避免資源枯竭和環境污染，對於高性能，低成本和環境友好的能源儲存裝置來說，合適的材料成為必不可少的因素。因此，生物質廢棄物的開發和再利用可以促進可持續能源新材料的探索，加強能源供應市場的價格競爭力，減輕對環境的污染，並且符合綠色與可持續發展戰略的迫切要求。
咖啡豆，廣泛存在於各個家庭和星巴克等咖啡店的一種現成的生物質原材料，在過去的幾年裡已經越來越受大眾的歡迎。在本文中，我們藉由一個綠色和低成本的化學活化的方法從咖啡渣中製作多孔碳並用於高性能超級電容器。我們還通過水熱法在泡沫鎳表面生長出氧化鈷奈米線陣列，並進一步將其做成高性能超級電容器電極。
對電極材料的形態和化學成分進行分析的方法包括X射線繞射（XRD），拉曼光譜，比表面積和孔隙率分析儀（BET），掃描電子顯微鏡（SEM），能量色散X射線光譜（EDX）和透射電子顯微鏡（TEM）。電化學性能採用循環伏安，定電流充放電測試和電化學阻抗譜（EIS）分析。
以氧化鈷作為正極和咖啡渣作為負極的非對稱超級電容器不但具有1.8伏特的高操作電壓，還有很高的能量密度（90.9 Wh/kg, 1623.7 W/kg）和功率密度（16200 W/kg, 63 Wh/kg），，在穩定性測試中也顯示了較好的循環壽命。並且將非對稱超級電容器串聯後，可以有效的驅動一個藍色LED指示燈和一個微型馬達。

因此，本文證明了以被視為毫無利用價值的咖啡渣作為前驅物，搭配高電容量氧化鈷奈米線陣列，製備成高性能非對稱超級電容器電極材料是可行的。並且其成本低廉、環境友好，且製備方式簡易，兼具廢物利用與綠色能源的特色，更可以對大自然減輕負擔，是一種極具潛力、理想的高性能非對稱超級電容器。

In order to match the increasing energy and to avoid resource depletion and environmental pollution, there is a demand for the development of high-performance, low cost and environmental-friendly energy storage devices. Suitable materials become the essential ingredients. So the development and utilization of biomass waste materials could boost the exploring of novel materials for sustainable energy, enhance price competitiveness in energy supply markets, relieve environmental pollution and match the urgent requirement for green and sustainable development strategies.
Coffee, a readily available biological material in kitchen and Starbucks, has become more and more popular to public in the past few years. In this paper, porous carbon were synthesized from coffee ground through a green and low-cost chemical activation method and used for high-performance supercapacitor materials. We also have developed an electrode composed of well-aligned cobalt oxide nanowire arrays which are grown on nickel foam surfaces fabricated by a facile hydrothermal approach and further investigated as the electrode for high-performance supercapacitors.
The morphology and chemical composition of the electrode materials were characterized by X-ray Diffraction (XRD), Raman spectroscopy, Surface Area and Porosimetry Analyzer (BET), Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Transmission electron microscope (TEM). The electrochemical properties are analyzed by using cyclic voltammetry, constant current charge-discharge measurement and Electrochemical Impedance Spectroscopy (EIS).
The pseudo supercapacitor device with a potential range from 0-1.8 V is consisted of the positive electrode (cobalt oxide) and coffee ground as the negative electrode has demonstrated high energy density (90.9 Wh/kg at 1623.7 W/kg), high power density (16200 W/kg at 63 Wh/kg) and an excellent long-term stability. Two pseudo supercapacitors connected in series can efficiently power a blue LED indicator and drive a mini motor.
This paper illustrated that the utilization of inexpensive precursors and universal resource taken from nature is an ideal way for the preparation of high performance supercapacitor electrode materials.

1. Lu, S.-M., et al., Development strategy of green energy industry for Taipei—A modern medium-sized city. Energy Policy, 2013. 62: p. 484-492.
2. Sebastian, R. and R. Pena Alzola, Flywheel energy storage systems: Review and simulation for an isolated wind power system. Renewable and Sustainable Energy Reviews, 2012. 16(9): p. 6803-6813.
3. Veluswamy, H.P., R. Kumar, and P. Linga, Hydrogen storage in clathrate hydrates: Current state of the art and future directions. Applied Energy, 2014. 122: p. 112-132.
4. Yoshino, A., 1 - Development of the Lithium-Ion Battery and Recent Technological Trends, in Lithium-Ion Batteries, G. Pistoia, Editor. 2014, Elsevier: Amsterdam. p. 1-20.
5. Nishi, Y., 2 - Past, Present and Future of Lithium-Ion Batteries: Can New Technologies Open up New Horizons?, in Lithium-Ion Batteries, G. Pistoia, Editor. 2014, Elsevier: Amsterdam. p. 21-39.
6. Karandikar, P.B., et al., Development, modeling and characterization of aqueous metal oxide based supercapacitor. Energy, 2012. 40(1): p. 131-138.
7. Shukla, A.K., et al., Electrochemical capacitors: Technical challenges and prognosis for future markets. Electrochimica Acta, 2012. 84: p. 165-173.
8. Hannan, M.A., F.A. Azidin, and A. Mohamed, Hybrid electric vehicles and their challenges: A review. Renewable and Sustainable Energy Reviews, 2014. 29: p. 135-150.
9. Miller, J.R. and A.F. Burke, Electrochemical capacitors: challenges and opportunities for real-world applications. The Electrochemical Society Interface, 2008. 17(1): p. 53.
10. Mansour, A., et al., Design and analysis of a high frequency DC–DC converters for fuel cell and super-capacitor used in electrical vehicle. International Journal of Hydrogen Energy, 2014. 39(3): p. 1580-1592.
11. Pandolfo, A.G. and A.F. Hollenkamp, Carbon properties and their role in supercapacitors. Journal of Power Sources, 2006. 157(1): p. 11-27.
12. Wenzl, H., BATTERIES | Capacity, in Encyclopedia of Electrochemical Power Sources, J. Garche, Editor. 2009, Elsevier: Amsterdam. p. 395-400.
13. Kurzweil, P., HISTORY | Electrochemical Capacitors, in Encyclopedia of Electrochemical Power Sources, J. Garche, Editor. 2009, Elsevier: Amsterdam. p. 596-606.
14. Sharma, P. and T.S. Bhatti, A review on electrochemical double-layer capacitors. Energy Conversion and Management, 2010. 51(12): p. 2901-2912.
15. Lin, N., et al., Hydrothermal synthesis of hydrous ruthenium oxide/graphene sheets for high-performance supercapacitors. Electrochimica Acta, 2013. 99: p. 219-224.
16. Patil, U.M., et al., Chemically synthesized hydrous RuO2 thin films for supercapacitor application. Journal of Alloys and Compounds, 2011. 509(5): p. 1677-1682.
17. Toupin, M., T. Brousse, and D. Belanger, Charge storage mechanism of MnO2 electrode used in aqueous electrochemical capacitor. Chemistry of Materials, 2004. 16(16): p. 3184-3190.
18. Liang, K., X. Tang, and W. Hu, High-performance three-dimensional nanoporous NiO film as a supercapacitor electrode. Journal of Materials Chemistry, 2012. 22(22): p. 11062-11067.
19. Rakhi, R., et al., Substrate dependent self-organization of mesoporous cobalt oxide nanowires with remarkable pseudocapacitance. Nano letters, 2012. 12(5): p. 2559-2567.
20. Lou, X.W.D., Growth of ultrathin mesoporous Co 3 O 4 nanosheet arrays on Ni foam for high-performance electrochemical capacitors. Energy & Environmental Science, 2012. 5(7): p. 7883-7887.
21. Cao, F., et al., Hydrothermal-synthesized Co(OH)2 nanocone arrays for supercapacitor application. Journal of Power Sources, 2012. 216: p. 395-399.
22. Zhi, M., et al., Nanostructured carbon-metal oxide composite electrodes for supercapacitors: a review. Nanoscale, 2013. 5(1): p. 72-88.
23. Riaz, U. and S.M. Ashraf, Conductive Polymer Composites and Blends. 2014: p. 509-538.
24. Zhang, Y., et al., Progress of electrochemical capacitor electrode materials: A review. International Journal of Hydrogen Energy, 2009. 34(11): p. 4889-4899.
25. Zhou, C., et al., Construction of high-capacitance 3D CoO@polypyrrole nanowire array electrode for aqueous asymmetric supercapacitor. Nano Lett, 2013. 13(5): p. 2078-85.
26. Huang, M., et al., Facile synthesis of hierarchical Co3O4@MnO2 core–shell arrays on Ni foam for asymmetric supercapacitors. Journal of Power Sources, 2014. 252: p. 98-106.
27. Gao, H., et al., High-performance asymmetric supercapacitor based on graphene hydrogel and nanostructured MnO2. ACS Appl Mater Interfaces, 2012. 4(5): p. 2801-10.
28. Jiang, H., et al., A green and high energy density asymmetric supercapacitor based on ultrathin MnO2 nanostructures and functional mesoporous carbon nanotube electrodes. Nanoscale, 2012. 4(3): p. 807.
29. Fan, Z., et al., Asymmetric supercapacitors based on graphene/MnO2 and activated carbon nanofiber electrodes with high power and energy density. Advanced Functional Materials, 2011. 21(12): p. 2366-2375.
30. Shen, J., et al., High-performance asymmetric supercapacitor based on nanoarchitectured polyaniline/graphene/carbon nanotube and activated graphene electrodes. ACS Appl Mater Interfaces, 2013. 5(17): p. 8467-76.
31. Cao, L., et al., Preparation of the Novel Nanocomposite Co(OH)2/ Ultra-Stable Y Zeolite and Its Application as a Supercapacitor with High Energy Density. Advanced Materials, 2004. 16(20): p. 1853-1857.
32. Huang, L., et al., Nickel–Cobalt Hydroxide Nanosheets Coated on NiCo2O4 Nanowires Grown on Carbon Fiber Paper for High-Performance Pseudocapacitors. Nano Letters, 2013. 13(7): p. 3135-3139.
33. Rakhi, R.B., et al., Substrate dependent self-organization of mesoporous cobalt oxide nanowires with remarkable pseudocapacitance. Nano Lett, 2012. 12(5): p. 2559-67.
34. Dong, X.-C., et al., 3D Graphene–Cobalt Oxide Electrode for High-Performance Supercapacitor and Enzymeless Glucose Detection. ACS Nano, 2012. 6(4): p. 3206-3213.
35. Wang, H., Z. Li, and D. Mitlin, Tailoring Biomass-Derived Carbon Nanoarchitectures for High-Performance Supercapacitors. ChemElectroChem, 2014. 1(2): p. 332-337.
36. Zhang, L., et al., High-Performance Supercapacitor Electrode Materials Prepared from Various Pollens. Small, 2013. 9(8): p. 1342-1347.
37. Yao, H., et al., Crab Shells as Sustainable Templates from Nature for Nanostructured Battery Electrodes. Nano Letters, 2013. 13(7): p. 3385-3390.
38. Wu, X.-L., et al., Biomass-Derived Sponge-like Carbonaceous Hydrogels and Aerogels for Supercapacitors. ACS Nano, 2013. 7(4): p. 3589-3597.
39. Huang, W., et al., Hierarchical porous carbon obtained from animal bone and evaluation in electric double-layer capacitors. Carbon, 2011. 49(3): p. 838-843.
40. Olivares-Marin, M., et al., Cherry stones as precursor of activated carbons for supercapacitors. Materials Chemistry and Physics, 2009. 114(1): p. 323-327.
41. Qian, W., et al., Human hair-derived carbon flakes for electrochemical supercapacitors. Energy & Environmental Science, 2014. 7(1): p. 379-386.
42. Guo, Y., et al., Performance of electrical double layer capacitors with porous carbons derived from rice husk. Materials chemistry and physics, 2003. 80(3): p. 704-709.
43. Subramanian, V., et al., Supercapacitors from activated carbon derived from banana fibers. The Journal of Physical Chemistry C, 2007. 111(20): p. 7527-7531.
44. Balathanigaimani, M., et al., Highly porous electrodes from novel corn grains-based activated carbons for electrical double layer capacitors. Electrochemistry Communications, 2008. 10(6): p. 868-871.
45. Raymundo‐Pinero, E., M. Cadek, and F. Beguin, Tuning carbon materials for supercapacitors by direct pyrolysis of seaweeds. Advanced Functional Materials, 2009. 19(7): p. 1032-1039.
46. Rufford, T.E., et al., Microstructure and electrochemical double-layer capacitance of carbon electrodes prepared by zinc chloride activation of sugar cane bagasse. Journal of Power Sources, 2010. 195(3): p. 912-918.
47. Elmouwahidi, A., et al., Activated carbons from KOH-activation of argan (< i> Argania spinosa</i>) seed shells as supercapacitor electrodes. Bioresource technology, 2012. 111: p. 185-190.
48. Marsh, H. and F.R. Reinoso, Activated carbon. 2006: Elsevier.
49. Wei, L., et al., Hydrothermal Carbonization of Abundant Renewable Natural Organic Chemicals for High-Performance Supercapacitor Electrodes. Advanced Energy Materials, 2011. 1(3): p. 356-361.
50. Otowa, T., R. Tanibata, and M. Itoh, Production and adsorption characteristics of MAXSORB: High-surface-area active carbon. Gas Separation & Purification, 1993. 7(4): p. 241-245.
51. Huang, C., T. Sun, and D. Hulicova-Jurcakova, Wide electrochemical window of supercapacitors from coffee bean-derived phosphorus-rich carbons. ChemSusChem, 2013. 6(12): p. 2330-9.
52. Jisha, M.R., et al., Electrochemical characterization of supercapacitors based on carbons derived from coffee shells. Materials Chemistry and Physics, 2009. 115(1): p. 33-39.
53. Rufford, T.E., et al., Nanoporous carbon electrode from waste coffee beans for high performance supercapacitors. Electrochemistry Communications, 2008. 10(10): p. 1594-1597.
54. Qian, W., et al., Human hair-derived carbon flakes for electrochemical supercapacitors. Energy & Environmental Science, 2014. 7(1): p. 379.
55. Li, X., et al., Preparation of capacitor's electrode from sunflower seed shell. Bioresour Technol, 2011. 102(2): p. 1118-23.
56. Rufford, T.E., et al., Double-layer capacitance of waste coffee ground activated carbons in an organic electrolyte. Electrochemistry Communications, 2009. 11(5): p. 974-977.
57. Endo, M., et al., Capacitance and pore-size distribution in aqueous and nonaqueous electrolytes using various activated carbon electrodes. Journal of the Electrochemical Society, 2001. 148(8): p. A910-A914.
58. Eliad, L., et al., Ion sieving effects in the electrical double layer of porous carbon electrodes: estimating effective ion size in electrolytic solutions. The Journal of Physical Chemistry B, 2001. 105(29): p. 6880-6887.
59. Zhao, X., C. Johnston, and P.S. Grant, A novel hybrid supercapacitor with a carbon nanotube cathode and an iron oxide/carbon nanotube composite anode. Journal of Materials Chemistry, 2009. 19(46): p. 8755-8760.
60. Demazeau, G., Solvothermal processes: a route to the stabilization of new materials. Journal of Materials Chemistry, 1999. 9(1): p. 15-18.
61. Novaconi, S. and N. Vaszilcsin, Inductive heating hydrothermal synthesis of titanium dioxide nanostructures. Materials Letters, 2013. 95(0): p. 59-62.
62. Lozano-Castello, D., et al., Carbon activation with KOH as explored by temperature programmed techniques, and the effects of hydrogen. Carbon, 2007. 45(13): p. 2529-2536.
63. Wang, J. and S. Kaskel, KOH activation of carbon-based materials for energy storage. Journal of Materials Chemistry, 2012. 22(45): p. 23710-23725.
64. Wang, H., Q. Gao, and J. Hu, High hydrogen storage capacity of porous carbons prepared by using activated carbon. Journal of the American Chemical Society, 2009. 131(20): p. 7016-7022.
65. Qiao, W., S.-H. Yoon, and I. Mochida, KOH activation of needle coke to develop activated carbons for high-performance EDLC. Energy & Fuels, 2006. 20(4): p. 1680-1684.
66. Świątkowski, A., Industrial carbon adsorbents. Studies in Surface Science and Catalysis, 1999. 120: p. 69-94.
67. Vielstich, W., Cyclic voltammetry. 2010: Wiley Online Library.
68. Kissinger, P.T. and W.R. Heineman, Cyclic voltammetry. Journal of Chemical Education, 1983. 60(9): p. 702.
69. Cao, L., et al., Preparation of the Novel Nanocomposite Co (OH) 2/Ultra‐Stable Y Zeolite and Its Application as a Supercapacitor with High Energy Density. Advanced materials, 2004. 16(20): p. 1853-1857.
70. Yu, H., et al., Using eggshell membrane as a separator in supercapacitor. Journal of Power Sources, 2012. 206: p. 463-468.
71. Orazem, M.E. and B. Tribollet, Electrochemical impedance spectroscopy. Vol. 48. 2011: John Wiley & Sons.
72. Ivers‐Tiffee, E., A. Weber, and H. Schichlein, Electrochemical impedance spectroscopy. Handbook of fuel cells, 2010.
73. Chang, B.-Y. and S.-M. Park, Electrochemical impedance spectroscopy. Annual Review of Analytical Chemistry, 2010. 3: p. 207-229.
74. Macdonald, J.R. and E. Barsoukov, Impedance spectroscopy: theory, experiment, and applications. History, 2005. 1: p. 8.
75. Retter, U. and H. Lohse, Electrochemical impedance spectroscopy, in Electroanalytical Methods. 2002, Springer. p. 149-166.
76. Lasia, A., Electrochemical impedance spectroscopy and its applications. 2002: Springer.
77. Macdonald, D.D., Reflections on the history of electrochemical impedance spectroscopy. Electrochimica Acta, 2006. 51(8-9): p. 1376-1388.
78. Pejova, B., et al., Fabrication and characterization of nanocrystalline cobalt oxide thin films. Materials Research Bulletin, 2001. 36(1–2): p. 161-170.
79. Kalpana, D., et al., Recycled waste paper—A new source of raw material for electric double-layer capacitors. Journal of Power Sources, 2009. 190(2): p. 587-591.
80. Biswal, M., et al., From dead leaves to high energy density supercapacitors. Energy & Environmental Science, 2013. 6(4): p. 1249.
81. Chen, W., et al., A fish scale based hierarchical lamellar porous carbon material obtained using a natural template for high performance electrochemical capacitors. Journal of Materials Chemistry, 2010. 20(23): p. 4773-4775.
82. Li, Q.-Y., et al., Novel activated carbons as electrode materials for electrochemical capacitors from a series of starch. Solid State Ionics, 2008. 179(7): p. 269-273.
83. Wang, X., et al., Dodecyl sulfate-induced fast faradic process in nickel cobalt oxide–reduced graphite oxide composite material and its application for asymmetric supercapacitor device. Journal of Materials Chemistry, 2012. 22(43): p. 23114.
84. Kong, L.-B., et al., Asymmetric Supercapacitor Based on Loose-Packed Cobalt Hydroxide Nanoflake Materials and Activated Carbon. Journal of The Electrochemical Society, 2009. 156(12): p. A1000.
85. Wang, X., et al., Enhancing electrochemical reaction sites in nickel-cobalt layered double hydroxides on zinc tin oxide nanowires: a hybrid material for an asymmetric supercapacitor device. Nanoscale, 2012. 4(22): p. 7266-72.
86. Yuan, A. and Q. Zhang, A novel hybrid manganese dioxide/activated carbon supercapacitor using lithium hydroxide electrolyte. Electrochemistry Communications, 2006. 8(7): p. 1173-1178.