Electrodeposition of Manganese and Molybdenum Mixed Oxide Thin Films and Their Charge Storage Properties

Abstract

Manganese and molybdenum mixed oxides in a thin film form were deposited anodically on a platinum substrate by cycling the electrode potential between 0 and +1.0 V vs Ag/AgCl in aqueous manganese(II) solutions containing molybdate anion (MoO(4)2-). A possible mechanism for the film formation is as follows. First, electrooxidation of Mn2+ ions with H2O yields Mn oxide and protons. Then, the protons being accumulated near the electrode surface react with MoO(4)2- to form polyoxomolybdate through a dehydrated condensation reaction (by protonation and dehydration). The condensed product coprecipitates with the Mn oxide. Cyclic voltammetry of the Mn/Mo oxide film-coated electrode in aqueous 0.5 M Na2SO4 solution exhibited a pseudocapacitive behavior with higher capacitance and better rate capability than that of the pure Mn oxide prepared similarly, most likely as a result of an increase in electrical conductivity of the film. Electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy clearly demonstrated that the observed pseudocapacitive behavior results from reversible extraction/insertion of hydrated protons to balance the charge upon oxidation/reduction of Mn3+/Mn4+ in the film.

A novel formaldehyde sensor based on the pseudocapacitive catalysis of birnessite

“…2a, the unmodified GC electrode exhibits no feature associated with FA, confirming no activity of GC toward oxidation of FA. H-and L-Bir/GCs in the absence of FA provide pseudocapacitive characteristics in the whole potential region examined, which can be attributed to continuous redox reactions of Mn 4+ /Mn 3+ accompanied with insertion/deinsertion of protons or electrolyte metals (Na + in the present case) into/from the oxide film [21]. The capacitive response of L-Bir/GC is larger than that of H-Bir/GC, probably reflecting its larger electroactive area.…”

“…The electrode coated with highly crystallized film gave rise to pseudocapacitive properties [21]. In this study, we found that the similarly-prepared film but composed of small birnesite crystallites exhibits high catalytic activity toward FA oxidation, which can be successfully applied to determine the concentration of FA.…”

Effects of the Co content in the material characteristics and supercapacitive performance of binary Mn–Co oxide electrodes

“…It was found in the literature that the incorporation of Ni [28,29], Pb [28], Mo [30], and V [31] oxides could enhance the specific capacitance of the Mn oxide. Nevertheless, the effects of Co oxide addition were not extensively studied [29,[32][33][34], and the experimental results from different research groups varied significantly.…”

Boron-doped MnO2/carbon fiber composite electrode for supercapacitor

“…They believed that the free electron metal atoms as electron donors can change the electronic structure of MnO 2 for a better conductivity and high capacitive performance. In fact, the doped materials do show better performance in magnetic, electrical and electrochemical properties, for example, cyclic voltammetry of the Mn/Mo oxide film-coated electrode exhibits a pseudocapacitive behavior with higher capacitance and better rate capability than that of the pure Mn oxide prepared similarly [15]. It is believed that if the radii of doping ion is lower but not so much than that of Mn 3+ ion and the bond between doping ion and O 2À is stronger than Mn-O bond, partial substitution of Mn 3+ ions may induce the reduction of lattice constant and the increase of Mn oxidation state, consequently, improving electrochemical properties [11,12].…”