Journal of Power Sources 190 (2009) 587–591 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Short communication Recycled waste paper—A new source of raw material for electric double-layer capacitors D. Kalpana a,c , S.H. Cho b , S.B. Lee b , Y.S. Lee b,∗ , Rohit Misra c , N.G. Renganathan d a The Research Institute for Catalysis, Chonnam National University, Gwangju 500-757, Republic of Korea b Faculty of Applied Chemical Engineering, Chonnam National University, Gwangju 500-757, Republic of Korea c National Environmental Engineering Research Institute, Nagpur 440 020, India d Central Electrochemical Research Institute, Karaikudi 630 006, India article info Article history: Received 17 November 2008 Received in revised form 12 December 2008 Accepted 4 January 2009 Available online 30 January 2009 Keywords: Activated carbon Newspaper Supercapacitor Potassium hydroxide activation Surface area abstract For the first time, a new carbon–carbon composite electrode material for supercapacitors is prepared by simple KOH activation of waste newspaper. The amorphous nature and surface morphology of the carbon composite are investigated by X-ray diffraction (XRD), N 2 adsorption/desorption and scanning electron microscopy. The surface area and pore diameter are 416 m 2 g -1 and 5.9 nm, respectively. Electrochemical characteristics are evaluated by cyclic voltammetry (CV) and charge–discharge tests in 6.0M KOH at a 1 mA cm -2 current density. The CV results reveal a maximum specific capacitance of 180 F g -1 at a 2 mV s -1 scan rate and the data explore a development of new use for waste paper into a valuable energy storage material. © 2009 Elsevier B.V. All rights reserved. 1. Introduction According to a recent report, approximately one-fifth of the contents of household dustbins consist of paper, of which half is newspaper and magazines. This is equivalent to over 4kg of wastepaper per household each week. Present approximations sug- gest that 80% of the waste stream is disposed as landfill, 10% is incinerated, and the other 10% is recycled. Recycling or reuse is the best current solution for reducing the disposal problem [1]. The magnitude of energy production from solid waste provides a small percentage of today’s soaring power demands. There is therefore an urgent need to supply alternate energy from other resources as some forms of fuels are approaching depletion. At present, activated carbon has been used as an electrode mate- rial in electrochemical double-layer capacitors (EDLCs) due to its high surface area and high capacitance. Activated carbon can be produced either by physical or chemical activation. In physical acti- vation, the raw material is carbonized under an inert atmosphere and then activated at high temperature using either steam or carbon dioxide as the activating reagent. In chemical activation, the precur- sor is treated with chemicals to help the initial hydration. Generally, chemical activation is the preferred route as it achieves higher yields, larger surface areas, low operating temperatures, and is cost- ∗ Corresponding author. Fax: +82 62 530 1909. E-mail address: drkalpanaa@gmail.com (D. Kalpana). effective [2,3]. The mesopores (diameter of 2–50 nm) of activated carbon can be produced with specific characteristics depending on the raw materials and the activation technique. The higher the con- tent of micropore, the better in order to obtain high capacitance values and a contribution of mesopores helps the mobility of ions through the porosity of the material. The micropores participate in the charge-storage processes and the mesopores are necessary for a fast accessibility of ions. We have chosen KOH as the oxidizing agent for the activation process as it can differentially improve the porosity of the materials. Two types of energy-storage mechanism have been studied in supercapacitors: electrochemical double-layer capacitors (EDLC) and pseudo-capacitors. In an EDLC, energy storage is accumulated from the electronic and ionic charges between an electrode and electrolyte interface. Porous carbons are attractive for EDLCs due to their large surface area, high pore accessibility, good thermal and chemical stability, and low cost. The energy storage in carbon-based supercapacitors involves charge separation at the high surface area carbon|electrolyte solution interface [4–6]. Various forms of car- bonaceous materials, such as bamboo, wood, cotton, banana fibre and camphor, have been employed as electrode precursors for EDLCs [7–11]. The high adsorption capacities of activated carbons are usually related to their specific surface area, pore volume and porosity [12]. In the present work, waste newspapers have been selected as the raw material for producing activated carbon. Waste newspa- per is a cheap raw material that can be used for supercapacitors 0378-7753/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2009.01.058