the fp was heated at 600  c for 30  min under n2 in order to fully remove the h2o and decompose cellulose , followed by carbonisation at 1000 , 1300 , 1500 and 1700  c for 30  min with a temperature ramp of 5  c min ( for an image of the carbonised fp , see supporting information ) .
scanning electron microscope ( s-4700 , hitachi , japan ) , atomic force microscope ( xe-100 , parksystems , korea ) , and an x - ray photoelectron spectroscope ( xps ) using an al k source ( 1486.6  ev ) were used to characterise the morphology , conductivity , and chemical composition of the fp samples .
xps peak position was calibrated to the adventitious c  1s peak at 285.0  ev .
electrochemical measurements were performed at room temperature ( 202  c ) with -autolab iii potentiostat ( eco - chemie , netherlands ) , running gpes software ( version 4.9 ) .
a pt wire served as a counter electrode and an ag / agcl electrode as the reference .
the carbonised fp was cut into small square piece of 0.7  cm diameter , and directly used as working electrode with a titanium plate as the current collector .
the capacitance was calculated by cyclic voltammetry and galvanostatic charge / discharge methods in a.c.s .
all solutions were prepared with milli - q water ( > 18  m  cm at 25  c ) .
the specific capacitance values calculated from the cv results are based on equation  ( 1 ) , where cv is the specific capacitance of an individual sample , is the total voltammetric charge obtained by integration of positive and negative sweep , e1 and e2 are the potential limits , m is the mass , and v is the scan rate . 

1 the specific capacitance values calculated from the gcd results are based on equation  ( 2 ) , where the i is discharge current , t is the discharging time , v is the potential drop during the discharge process in the range of vmax and  vmax , and m is the mass for the electrode materials .
a scan rate of 5  mv  s was used for gcd measurements used to calculate the specific capacitance . 
 2
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 advanced carbon materials are important for the next - generation of energy storage apparatus , such as electrochemical capacitors . here 
 , the physical and electrochemical properties of carbonised filter paper ( fp ) were investigated . 
 fp is comprised of pure cellulose and is a standardised material . 
 after carbonisation at temperatures ranging from 600 to 1700  c , fp was contaminant - free , containing only carbon and some oxygenated species , and its primary fibre structure was retained ( diameter 2040  m ) . 
 the observed enhancement in conductivity of the carbonised fp was correlated with the carbonisation temperature . 
 electrochemical capacitance in the range of 1.8117  f  g1 was achieved , with fp carbonised at 1500  c showing the best performance . 
 this high capacitance was stable with > 87  % retained after 3000 charge  
 discharge cycles . 
 these results show that carbonised fp , without the addition of composite materials , exhibits good supercapacitance performance , which competes well with existing electrodes made of carbon - based materials . 
 furthermore , given the lower cost and renewable source , cellulose - based materials are the more eco - friendly option for energy storage applications . 
Experimental Section
Supporting Information