Ammonia Treatment of Activated Carbon Powders for Supercapacitor Electrode Application

Microporous activated carbon powder was modified by ammonia gas or ammonia/nitrogen mixture at elevated temperatures with different duration in order to obtain supercapacitor electrode materials with enhanced capacitance. XPS analysis showed higher amount of nitrogen containing functional groups (up to 4.5 at%) incorporated into carbon powders which were oxidized before ammonia treatment. The highest amount of N was introduced by treatments at 400°C, whereas extensive activation was observed after treatment at 800°C. The modified carbon powders demonstrated an increase in gravimetric capacitance up to 30% in 1 mol dm−3 H2SO4 solution. During 10,000 constant current charge/discharge cycles, the capacitance decreased by 2.5 to 10%, depending on the modified material used.