Dynamic Electrodeposition of Manganese Dioxide: Temporal Variation in the Electrodeposition Mechanism

Abstract

The time resolved mechanism of electrodeposition and the effect of this changing mechanism on the nucleation and growth of solid manganese dioxide has been investigated in both acidic and neutral electrolytes on the rotating ring disc electrode (RRDE). The fate of the Mn 3+ intermediate is a key feature of this electrodeposition mechanism, the formation of which is dependent on the substrate, which in this case is either platinum, MnO 2 or MnOOH. On the platinum surface, for all electrolytes, soluble Mn 3+ is produced initially. The stability of this soluble Mn 3+ species determines the initial morphology, and rate of change of mechanism for the process. In a neutral electrolyte, nucleation and growth of MnO 2 occurs primarily through the precipitation of a 2D film of MnOOH on the platinum, which rapidly covers the surface. Nucleation in an acidic H 2 SO 4 system occurs primarily via a disproportionation route which forms 3D MnO 2 hemispheroids that cover the substrate slowly. Subsequent growth of MnO 2 in both electrolytes then proceeds via formation of a MnOOH film, which is subsequently oxidized in the solid state to form MnO 2 . MnOOH oxidation to MnO 2 appears kinetically limited, which is overall a limiting factor in the electrodeposition process.

Mn3O4@NC Composite Nanorods as a Cathode for Rechargeable Aqueous Zn‐Ion Batteries

“…Due to the activation, the specific capacity increases in the initial cycles. [13,27,49,50] The storage and reaction mechanisms were studied by CV and EIS tests to further discover the underlying cause for the improvement of electrochemical performance of Mn 3 O 4 @NC Nrs electrode. Even measured at higher current density of 1000 mA g À 1 , Mn 3 O 4 @NC Nrs can also exhibit a satisfactory capacity of 97 mAh g À 1 after 700 cycles (Figure 6e).…”

“…[44,47,48] The reasonable explanations can be ascribed to two aspects: (1) the reversible reactions and low electrochemical activities of active materials are caused by the infiltration of the electrolyte to the cathode, and (2) the synergistic effect of Zn 2 + and Mn 2 + and the redox reaction effect of Mn 2 + exist in electrolyte, which restrain the structural collapse and aggregation of active materials and diminish the generation of other impurities reducing the performances of ZIBs. [13,27,49,50] The storage and reaction mechanisms were studied by CV and EIS tests to further discover the underlying cause for the improvement of electrochemical performance of Mn 3 O 4 @NC Nrs electrode. Figure 7a showed the CV curves of Mn 3 O 4 @NC Nrs conducted at different scan rates centering from 0.1-5.0 mV s À 1 .…”

Electrodeposition of Adherent Submicron to Micron Thick Manganese Dioxide Films with Optimized Current Collector Interface for 3D Li-Ion Electrodes

“…10,11,22,23 The general mechanism is 3+ stability, which can further either diffuse out from the electrode surface to the bulk of the solution (initially) or precipitate as a passivating MnOOH layer. In the latter case, oxidation of MnOOH to form MnO 2 needs to happen to open up a site for the reaction to continue, which was identified as the limiting factor in the growth process.…”

“…In the latter case, oxidation of MnOOH to form MnO 2 needs to happen to open up a site for the reaction to continue, which was identified as the limiting factor in the growth process. 11 The MnO 2 formation mechanism is as follows:…”

“…Various substrates have been used for the electrodeposition of MnO 2 material for their use in electrochemical capacitors or batteries. [11][12][13][14] The importance of substrate variation for the EMD deposition mechanism has been highlighted but not given much attention.…”