Efficient Capacitor Materials from Active Carbons Based on Coconut Shell/Melamine Precursors

Specially elaborated technology for the preparation of active carbon has allowed us to obtain a series of samples with a highly developed Brunauer-Emmett-Teller (BET) surface of over 3000 m(2)/g, very high total pore volume of over 2 cm(3)/g, and high nitrogen content of up to 5.9 atomic %. Materials are characterized by an extremely developed nanostructure in a small mesopore region (2-3.5 nm). X-ray photoelectron spectroscopy (XPS) analysis shows the entire lack of pyridinic nitrogen (N-6) and considerable amount of oxygen, mainly in the form of phenolic surface groups (OH). which is very helpful in obtaining high-capacitance properties. This is confirmed by the results of extended electrochemical examinations. Material with the highest level of nitrogen enrichment reveals excellent capacitance characteristics if employed as both the negative and positive electrode in an acidic capacitor (307 and 293 F/g, respectively) or the negative electrode in an alkaline capacitor (368 F/g). This paper discusses the influence of nitrogen and oxygen functionality on capacitance properties of active carbons, especially on the charge-exchange dynamic of electrodes of both polarities in acidic and alkaline electrolytes.