Abstract
We report here an efficient single step combined sonochemical and solvothermal synthesis process to obtain bulk quantities of nanospherical particles of cubic Mn2O3 and characterized its pseudocapacitive characteristics in relevance to electrochemical capacitors for the first time. It has been found that quantitative determination of specific capacitance yielded a value of capacitance of ∼100 Fg−1 within 0–0.4 V (versus SCE) potential range in a 6 M KOH alkaline electrolyte. The as‐prepared nanopowders after being subjected to heat treatment at 400 ∘C were characterized by using XRD which shows a typical cubic single‐phase structure (space group Ia-3), the broad crystalline peaks indicating the presence of explicit nanostructure. Electron microscopic studies (FE‐SEM and TEM) revealed that the synthesized powders exhibit nanospherical morphology with uniform sphere‐like grains of ∼10–15 nm range. Two heat‐treated samples were studied in the context of crystallinity versus electrochemical capacitance using rate‐dependent cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a three‐electrode system. The excellent well‐refined redox behavior corroborates with EIS measurements. The presence of near symmetric redox couple observed in CV has been attributed to pronounced one‐electron‐transfer process owing to the presence of facile Mn redox centers facilitating the reversible one‐electron transfer that accounts for its pseudocapacitance.
Highlights
The concept of electrochemical capacitor was initialized and industrialized almost 40 years ago, the demand for high power pulse requirements in today’s modern power hunger electrical and electronic devices such as telecommunication devices standby power systems, memory protection of computer electronics, and hybrid electric vehicles in the form of storage components rendered a renewed interest in electrochemical capacitors (ECs)
The hkl planes are well-indexed to a cubic phase with lattice parameter a = 9.4080 Ahaving broad crystalline peaks indicating the presence of explicit nanostructure
As the holding time is increased from 1 hour to 5 hours, while maintained at 400◦C, X-ray diffraction (XRD) peaks became relatively sharper yet maintaining the features corresponding to its nanostructure
Summary
The concept of electrochemical capacitor was initialized and industrialized almost 40 years ago, the demand for high power pulse requirements in today’s modern power hunger electrical and electronic devices such as telecommunication devices (mobile phones, PDA, etc.) standby power systems, memory protection of computer electronics, and hybrid electric vehicles in the form of storage components rendered a renewed interest in electrochemical capacitors (ECs) Depending on their charge storage mechanism, ECs utilize both nonfaradic and faradic capacitance, namely, electrochemical double-layer capacitance (EDLC) and pseudocapacitance, respectively. MnO2 is one of the common manganese oxide phases which are extensively investigated because of its applications as catalysts in ion sieves, as electrode materials in primary Li/MnO2 batteries as well as in electrochemical capacitors [15,16,17,18,19,20,21]. Using the rate-dependent cyclic voltammetry, a single electrode pseudocapacitance behavior of Mn2O3 nanosphere electrodes has been studied using a three-electrode cell comprised of a platinum counter and SCE as reference electrodes in alkaline medium (6 M KOH)
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