MnCO3 as an electrode material for supercapacitor is slowly gaining momentum. So far, wet chemical methods have been used to synthesize MnCO3 for supercapacitor applications. The electrode fabrication of thus prepared MnCO3 requires a certain percentage of conductive additive and binder; both of them do not contribute significantly to the measured capacitance. Herein, we report electrodeposition of MnCO3 and its capacitance properties. MnCO3 has been electrodeposited from an aqueous mixture of MnSO4 and Na3C6H5O7 by chronopotentiometry. X‐ray diffraction and Raman spectroscopic studies confirm the formation of MnCO3. Microscopic studies reveal the formation of micron‐sized spherical particles by the agglomeration of sub‐micron sized cubes. Electrodeposited MnCO3 delivers a specific capacitance of 194 F g−1 at a specific current of 0.5 A g−1 and demonstrates good rate capability. Further, it also exhibits high cycling stability over 10,000 cycles with retention of 92% of its initial specific capacitance value and 100% coulombic efficiency.

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Nanocrystalline MnCO 3 is synthesized by hydrothermal reduction of KMnO 4 using different amounts of pyrrole. The effect of molar ratio of KMnO 4 :pyrrole on the phase purity, size of the particle, textural and capacitance properties of MnCO 3 is studied systematically using various physico-chemical and electrochemical techniques. While X-ray diffraction studies confirm decline in the phase purity of MnCO 3 , FTIR, Raman spectroscopic and thermogravimetric studies reveal an increase in the amount of adsorbed water and residual carbon content on increasing the pyrrole concentration during the synthesis. An increase in the size of the particles and reduction in the number of mesopores are observed from the morphological and sorption studies on increasing the pyrrole concentration during the synthesis. A highest specific capacitance value of 296 F g −1 is obtained at a current density of 0.16 A g −1 for the nanocrystalline MnCO 3 , and this capacitance value found to decrease on increasing the concentration of pyrrole during the synthesis of nanocrystalline MnCO 3 (166 and 140 F g −1 for the KMnO 4 :pyrrole ratio of 1:1 and 1:2, respectively).

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Synthesis of mesoporous graphitic carbon nitride (MGCN) by soft template method is still challenging and its application as an electrode material for supercapacitor remains unexplored. Herein, we introduce MGCN as an electrode material for supercapacitors. MGCN is synthesized by facile direct carbonization of methylolated surfactant-polymer composite and bulk graphitic carbon nitride (BGCN) is synthesized under similar condition but in the absence of surfactant. MGCN displays excellent capacitance properties in 1 M H 2 SO 4 electrolyte with a specific capacitance as high as 279 F g À 1 at a current density of 0.25 A g À 1 . It also exhibits good rate capability and outstanding cycling stability with excellent coulombic efficiency of 100% over 5000 cycles. This superior capacitive storage performance is attributed to the high surface area, easily accessible mesopores and high pyridinic nitrogen content. High surface area and uniform pores of MGCN provide more active sites for charge storage and reduce diffusion path length for ions while high pyridinic nitrogen enhanced the overall specific capacitance by surface Faradaic reaction.