Tuning the Capacitance Properties of Nanocrystalline MnCO₃by the Effect of a Carbonizing Agent

Abstract

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).

Unveiling Mesoporous Graphitic Carbon Nitride as a High Performance Electrode Material for Supercapacitors

“…The R s and R ct were computed by fitting impedance spectra using an equivalent circuit shown in Figure c. It is well known that poor cycling stability of the electrode material is attributed to instability of the material causing phase change or dissolution during cycling, increase in the internal resistance of the material, etc ,. Owing to the high chemical and structural stability of MGCN, it neither undergone dissolution nor phase change during extended cycling as reflected in Figure a.…”

The Charge Storage Mechanism of MnCO3 in Aqueous Electrolytes

“…It has been reported that some of the metal oxides undergo phase transformation during extended GCD cycling . Nevertheless, MnCO 3 retains its phase even after 500 GCD cycles in aqueous 0.1 M Mg(ClO 4 ) 2 electrolyte (Figure d) …”

“…In addition, it also exhibits electrochromism . Most importantly, MnCO 3 is studied extensively as an anode material in lithium‐ion batteries, and as an electroactive material in supercapacitors …”

“…The capacitance properties of MnCO 3 are studied in either slightly acidic (Na 2 SO 4 , NaClO 4 , Mg(ClO 4 ) 2 ), or alkaline (KOH) electrolytes. The specific capacitance value in the range of 100 to 300 F g −1 reported for MnCO 3 and its composites is believed to arise from both the mechanisms, i. e., adsorption/desorption of ions at the electrode/electrolyte interface resulting in the formation of electric double layer and pseudocapacitance. However, the charge compensation at the Mn sites remains unclear.…”

MnCO3 on Graphene Porous Framework via Diffusion-Driven Layer-by-Layer Assembly for High-Performance Pseudocapacitor

“…Commonly studied materials include metal oxides or metal hydroxides such as RuO 2 , MnO 2 , Co 3 O 4 , Ni­(OH) 2 , and Co­(OH) 2 . − Although these compounds provide significantly higher theoretical capacitance than carbon materials, their actual performance generally suffers due to poor conductivity and stability. As such, alternative pseudocapacitor materials with improved properties are continuously being sought after, MnCO 3 being one of them. − Various methods have been used to synthesize MnCO 3 nanostructures with different morphologies and compositions. For example, micron-sized spheres comprised of agglomerated submicron MnCO 3 cubes were prepared by electrodeposition from an aqueous mixture of MnSO 4 and Na 3 C 6 H 5 O 7 .…”