Investigation on the pseudocapacitive charge storage mechanism of MnO2 in various electrolytes by electrochemical quartz crystal microbalance (EQCM)

Effect of strontium doping on the electrochemical pseudocapacitance of Y1−xSrxMnO3−δ perovskites

“…The charge storage mechanism in perovskites could be completed through the cation reduction process, which leads to O 2À ions interconversion into OH À through the incorporation or diffusion of water into the structure. [30][31][32][33][34][35][36][37] The peaks at À0.25 and À0.6 V correspond to the reduction of Mn 3+ to Mn 2+ , and Mn 4+ to Mn 3+ , respectively. The peaks centered at À0.12 V and À0.42 V correspond to the oxidation of Mn 2+ to Mn 3+ and Mn 3+ to Mn 4+ respectively.…”

“…29 Hence, interconversion of oxide ion into hydroxide ion is not limited due to size difference and is kinetically favorable in resulting in high redox-mediated capacitance in the materials such as RuO 2 and MnO 2 where the presence of hydrated H 2 O plays an active role in resulting high pseudocapacitance due to reversible proton intercalation. [30][31][32][33][34][35][36][37] In the present work, Sr-doped YMnO 3 samples were successfully synthesized by the solid-state ceramic route, and their electrochemical pseudocapacitance as anode materials were investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance methods. In stoichiometric YMnO 3 , the Mn is present usually in a +3 oxidation state, as we dope low-valence Sr atom at Y sites, Mn 3+ oxidized to +4 oxidation state which may lead to the lattice distortion in YMnO 3 structure and enhanced electrical conductivity in the materials through Mn 3+ -O 2À -Mn 4+ hopping conduction.…”

“…29 Hence, interconversion of oxide ion into hydroxide ion is not limited due to size difference and is kinetically favorable in resulting in high redox-mediated capacitance in the materials such as RuO 2 and MnO 2 where the presence of hydrated H 2 O plays an active role in resulting high pseudocapacitance due to reversible proton intercalation. 30–37…”

Scalable Synthesis of Pre‐Intercalated Manganese(III/IV) Oxide Nanostructures for Supercapacitor Electrodes: Electrochemical Comparison of Birnessite and Cryptomelane Products

“…[15,29,[32][33][34][35][36] In addition, the form of the MnO z polymorph is known to play a critical role in capacitance decay; for instance, it has been shown that Jahn-Teller distortions of MnO 6 octahedra cause less disruption to the two-dimensional channels of δ-MnO z than the corresponding ion pathways of α-MnO z . [37] Although numerous investigations into the electrochemical behaviors of MnO z materials have addressed how storage performance depends on factors such as crystallographic phase [22,[37][38][39][40][41][42][43][44] and the nature of intercalating cations, [11,14,25,31,[45][46][47][48][49][50][51][52][53][54] the effects of guest cation type and MnO z structure are rarely explored simultaneously within a single self-consistent study. Furthermore, researchers have hitherto adhered to a convention of measuring storage parameters as functions of current density and potential scan rate at just one stage during testing, either with the electrode in its as-prepared state or after a designated number of activation cycles.…”

Deciphering the Influence of Electrolytes on the Energy Storage Mechanism of Vertically-Oriented Graphene Nanosheet Electrodes by Using Advanced Electrogravimetric Methods

“…Thus, EQCM provided useful information, as for example, dealing with the effects and role of (de)solvation, electro-adsorption/desorption of both anions and cations and its ionic exchange behavior on nano/micro-porous carbon during the charge-discharge cycles. To date, EQCM has been widely employed for thin planar films based on carbonaceous structures such as carbon nanotubes or nanoporous carbon [41], pseudocapacitive materials such as transition metal oxides (MnO 2 ) [42,43] or nitrides (e.g. vanadium nitrides) [44].…”