Reversible Redox Transition and Pseudocapacitance of Molybdenum/Surface Molybdenum Oxides

Abstract

Redox transitions and superior pseudocapacitance are two typical characteristics in the electrochemical behavior of metallic Mo (with surface Mo oxides) and bulk Mo oxides; both of which were attributed to the participation of H+/cations. The effects of different electrolyte anions (Cl−, SO42− and ClO4−) on redox transition and pseudocapacitance of thin-film ‘Mo/Mo oxides’ electrodes were assessed in this work through DC and AC electrochemical experiments. Voltammetric peak potentials and currents and potential-dependent pseudocapacitance were strongly dependent on the electrolyte's anion. The variations were tested at different electrolyte pH levels and using different electrolyte cations (Li+, Na+ and K+). The results were correlated with those obtained using a Se4+ based electrolyte. The findings reported here are expected to aid the applicability of Mo and its oxides in electrocatalysis, electrodeposition, supercapacitor, display, corrosion control and solar cells.

Electrodeposition of Copper, Selenium, Indium, and Gallium on Molybdenum/Surface Oxides: Unary, Binary, Ternary and Quaternary Compositions

“…28,33 This result is consistent with the earlier report by Petitl et al, 41 where the authors showed that mass transfer limited slow electrodeposition of In on Mo cannot be detected with traditional CV. However, In deposited surface modifications of Mo were readily detected with optical second harmonic generation.…”

“…The decrease in C p after reaching a maximum can be associated with the hydrogen evolution process. 28 (b) Selenium CV recorded in Se(IV) electrolyte showed primarily two reduction peaks, C 1 and C 2 (Figures 2A-2C), where C 1 could be attributed to surface oxide's reduction 28 and C 2 to H 2 Se formation (Eq. 5).…”

“…C p was obtained by curve fitting the EIS plots recorded at a series of potentials using a software controlled batch process (Nova 1.6, FRA potential scan). 28,29 EIS plots were recorded at regular intervals at 40 different potentials (at each potential corresponding to each point in the capacitance-potential plot) between −0.05 and −1.0 V; under 0.01 V AC signals over the frequency range of 10 −1 to 10 5 Hz. The estimated error in determining C p by curve fitting was always less than 10%.…”

Electrochemical Multi-Coloration of Molybdenum Oxide Bronzes

“…The first peak can be attributed to the characteristic redox transition of Mo oxides. 8,13 The second peak may be due to a subsequent Mo oxide's reduction. Both the peaks were accompanied with a frequency decrease indicating mass gain.…”

“…13 In this work, we wish to report our findings on the electrochemical multi-coloration of surface Mo oxide bronzes electrochemically derived from Mo in neutral aqueous solutions. To the best of our knowledge this is the first report on the fabrication of red, blue, and yellow colored bronzes on Mo in aqueous solution by an electrochemical strategy.…”