Carbon Monoliths with Hierarchical Porous Structure for All-Vanadium Redox Flow Batteries Articles uri icon

authors

  • VIVO VILCHES, JOSE FRANCISCO
  • Karakashov, Blagoj
  • Celzard, Alain
  • Fierro, Vanessa
  • El Hage, Ranine
  • Brosse, Nicolas
  • Dyfour, Anthony
  • Etienne, Mathieu

publication date

  • September 2021

start page

  • 1

end page

  • 15

issue

  • 3

volume

  • 7

International Standard Serial Number (ISSN)

  • 2313-0105

abstract

  • Carbon monoliths were tested as electrodes for vanadium redox batteries. The materials
    were synthesised by a hard-templating route, employing sucrose as carbon precursor and sodium
    chloride crystals as the hard template. For the preparation process, both sucrose and sodium chloride
    were ball-milled together and molten into a paste which was hot-pressed to achieve polycondensation
    of sucrose into a hard monolith. The resultant material was pyrolysed in nitrogen at 750 ◦C, and
    then washed to remove the salt by dissolving it in water. Once the porosity was opened, a second
    pyrolysis step at 900 ◦C was performed for the complete conversion of the materials into carbon.
    The products were next characterised in terms of textural properties and composition. Changes in
    porosity, obtained by varying the proportions of sucrose to sodium chloride in the initial mixture,
    were correlated with the electrochemical performances of the samples, and a good agreement
    between capacitive response and microporosity was indeed observed highlighted by an increase
    in the cyclic voltammetry curve area when the SBET increased. In contrast, the reversibility of
    vanadium redox reactions measured as a function of the difference between reduction and oxidation
    potentials was correlated with the accessibility of the active vanadium species to the carbon surface,
    i.e., was correlated with the macroporosity. The latter was a critical parameter for understanding
    the differences of energy and voltage efficiencies among the materials, those with larger macropore
    volumes having the higher efficiencies.

keywords

  • vanadium redox flow battery; hierarchical carbon; carbon electrode; porosity; sucrosebased carbon monolith