Mass transfer to horizontal gas-generating electrodes

Нефедов, В. Г.; Artyushenko, O. A.; Kashevarova, E. V.

doi:10.1134/s1023193506060073

Cited by 5 publications

(3 citation statements)

References 18 publications

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“…Due to the considerable convection, the Nernst diffusion layer is small and consistent in the three independent experiments [d = (60-75) lm]. Although bubbles could not be seen or detected, it is nevertheless possible to assess the influence of convection with its key variable d. The Nernst diffusion layer thickness is very small, but such small diffusion layers at macroscopic electrodes have been measured before for the oxygen evolution reaction [55]. SECM also appears to be a good method to study convection at gas evolving electrodes, i.e.…”

Section: Secm Measurements Of Diffusion Layersmentioning

confidence: 95%

New oxygen evolution anodes for metal electrowinning: investigation of local physicochemical processes on composite electrodes with conductive atomic force microscopy and scanning electrochemical microscopy

Schmachtel¹,

Pust

Kontturi³

et al. 2009

J Appl Electrochem

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Atomic force microscopy (AFM), conductive atomic force microscopy (CAFM) in air, and scanning electrochemcial microscopy (SECM) in 2 M H 2 SO 4 have been used to investigate model composite electrodes obtained by pressing sieved MnO 2 particles into a Pb matrix. These model electrodes shall resemble new composite electrodes produced by coldspraying and currently being tested for Zn electrowinning. CAFM showed a very uneven distribution of the current path through the matrix electrode with the highest currents measured at the MnO 2 / Pb domain boundary. SECM images in the substrate-generation/tip-collection mode in vertical and horizontal planes could show spatial concentration distribution of H ? , O 2 and H 2 O 2 that could be evaluated qualitatively despite interfering turbulent convection due to raising gas bubbles. There is a concentration overvoltage due to deviations of the H ? and O 2 concentration close to the surface from the bulk value. It amounts to about 40-50 mV for both compounds. H 2 O 2 is formed as an intermediate and is consumed at the MnO 2 catalyst particles.

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Section: Secm Measurements Of Diffusion Layersmentioning

confidence: 95%

New oxygen evolution anodes for metal electrowinning: investigation of local physicochemical processes on composite electrodes with conductive atomic force microscopy and scanning electrochemical microscopy

Schmachtel¹,

Pust

Kontturi³

et al. 2009

J Appl Electrochem

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“…It is beyond the scope of this paper to review the topic of hydrodynamics of electrochemically generated gases [34] but it is important to evaluate the magnitude of the mass-transfer enhancement achievable by gas generation at the anode. Most experimental data and available models obtained in aqueous electrolytes [35,36,37] suggest a potential ten-fold increase in the mass-transfer coefficient for gas generation at a current density higher than 1000 A.m -2 . All things being equal, such tenfold enhancement of the free-convection case (equation 9) would justify the experimental current density reported for oxygen evolution in molten oxides.…”

Section: Other Contributions To Mass-transfer During Oxygen Evolutionmentioning

confidence: 99%

Electrochemical engineering of anodic oxygen evolution in molten oxides

Allanore

2013

Electrochimica Acta

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Molten oxide electrolysis (MOE) is a metal extraction process that exhibits an exceptionally high productivity in comparison with other electrowinning techniques.Furthermore, MOE has the ability to generate oxygen as an environmentally benign byproduct, which is a key asset to improve metal extraction sustainability. From an electrochemical engineering standpoint, the high concentration of metal cations dissolved in the electrolyte justifies cathode current densities above 10 000 A.m -2 . At the anode, the available data suggest a mechanism of oxidation of the free oxide anions which concentration in oxide melts is reported to be limited. In this context, the application of available mass-transfer correlations for the anodic oxygen evolution suggests a key role of convection induced by gas bubbles evolution.

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“…A novel ring microelectrode encircling a hydrophobic microcavity was effective in avoiding bubble coverage in AWE, and the cell voltage is lower than those associated with conventional microelectrodes [13] . In addition, the tuning of flow fields [14] , magnetic fields [15] , [16] , acoustic fields [17] , [18] , and electrolyte formulation [19] can mitigate the impact of bubbles on the overpotential of the electrolysis system. Nonetheless, although the above methods can mitigate bubble-induced energy losses, they also add complexity due to the addition of auxiliary measures in the electrolysis systems [20] .…”

Section: Introductionmentioning

confidence: 99%