N-doped porous carbon film electrodes for electrochemical capacitor, made by electrospray of precursor sol

Abstract Heteroatom doping in carbon structure enhances surface wettability, electrical conductivity, and electron-donor/acceptor properties that in turn, improves the electrochemical performance of carbon electrodes. In this article, in situ grown carbon film electrodes are obtained through electrospray of polymeric sol on carbon paper, followed by curing, and carbonization. The nitrogen functionality in these binder-free carbon film electrodes is successfully incorporated from melamine addition in resorcinol-formaldehyde sol. The film electrode shows a capacitance of 223 mF cm−2 (446 F g−1), and volumetric energy density of 15.2 mWh cm−3 at 1 mA cm−2 in a symmetric cell with 2 M KOH as electrolyte. Furthermore, these electrodes exhibit excellent cyclic stability even after 5000 charge-discharge cycles with almost complete capacitance retention at 5 mA cm−2. The outstanding electrochemical performance of carbon film electrodes are due to the combined effect of following steps: (i) incorporation of nitrogen and oxygen in right amount, (ii) retention of the desired pore size distribution, and fraction of micropores through systematic balancing of resorcinol to melamine ratio in precursor sol, (iii) disintegration of sol by electrospray prior to deposition on carbon paper, that in turn produces a porous three-dimensional interconnected network of nanoparticulate film, and (iv) lyophilization of wet gel layer that retains the pore spaces during solvent removal.