Spin-coated vs. electrodeposited Mn oxide films as water oxidation catalysts

Simelys Hernández, CARMINNA SOPHIA OTTONE MELIS, Sara Varetti, Marco Fontana, Diego Pugliese, Guido Saracco, Barbara Bonelli, Marco Armandi

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Manganese oxides (MnOx), being active, inexpensive and low-toxicity materials, are considered promising water oxidation catalysts (WOCs). This work reports the preparation and the physico-chemical and electrochemical characterization of spin-coated (SC) films of commercial Mn2O3, Mn3O4 and MnO2 powders. Spin coating consists of few preparation steps and employs green chemicals (i.e., ethanol, acetic acid, polyethylene oxide and water). To the best of our knowledge, this is the first time SC has been used for the preparation of stable powder-based WOCs electrodes. For comparison, MnOx films were also prepared by means of electrodeposition (ED) and tested under the same conditions, at neutral pH. Particular interest was given to α-Mn2O3-based films, since Mn (III) species play a crucial role in the electrocatalytic oxidation of water. To this end, MnO2-based SC and ED films were calcined at 500 °C, in order to obtain the desired α-Mn2O3 crystalline phase. Electrochemical impedance spectroscopy (EIS) measurements were performed to study both electrode charge transport properties and electrode-electrolyte charge transfer kinetics. Long-term stability tests and oxygen/hydrogen evolution measurements were also made on the highest-performing samples and their faradaic efficiencies were quantified, with results higher than 95% for the Mn2O3 SC film, finally showing that the SC technique proposed here is a simple and reliable method to study the electrocatalytic behavior of pre-synthesized WOCs powders.

Original languageEnglish
Article number296
JournalMaterials
Volume9
Issue number4
DOIs
StatePublished - 1 Jan 2016

Keywords

  • Electrochemical impedance spectroscopy
  • Electrodeposition
  • Manganese oxides films
  • Polyethylene oxide
  • Water oxidation

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