Catalytic Reactivation of Industrial Oxygen Depolarized Cathodes by in situ Generation of Atomic Hydrogen. Issue 12 (22nd May 2019)

• Record Type: Journal Article
• Authors: Öhl, Denis; Franzen, David; Paulisch, Melanie; Dieckhöfer, Stefan; Barwe, Stefan; Andronescu, Corina; Manke, Ingo; Turek, Thomas; Schuhmann, Wolfgang
• Is Part Of: ChemSusChem. Volume 12:Issue 12(2019)
• Page Start: 2732
• Page End: 2739
• Publication Date: 2019-05-22
• Subjects: catalyst regeneration -- cathode -- chlor-alkali electrolysis -- depolarization -- gas diffusion electrode; Green chemistry -- Periodicals; Sustainable engineering -- Periodicals; Chemistry -- Periodicals; Chemical engineering -- Periodicals; 660
• DOI: 10.1002/cssc.201900628
• Languages: English
• ISSNs: 1864-5631

Abstract

Abstract: Electrocatalytically active materials on the industrial as well as on the laboratory scale may suffer from chemical instability during operation, air exposure, or storage in the electrolyte. A strategy to recover the loss of electrocatalytic activity is presented. Oxygen‐depolarized cathodes (ODC), analogous to those that are utilized in industrial brine electrolysis, are analyzed: the catalytic activity of the electrodes upon storage (4 weeks) under industrial process conditions (30 wt % NaOH, without operation) diminishes. This phenomenon occurs as a consequence of surface oxidation and pore blockage, as revealed by scanning electron microscopy, focused ion beam milling, X‐ray photoelectron spectroscopy, and Raman spectroscopy. Potentiodynamic cycling of the oxidized electrodes to highly reductive potentials and the formation of "nascent" hydrogen re‐reduces the electrode material, ultimately recovering the former catalytic activity. Abstract : Depolarization reversed : Oxygen‐depolarized cathodes used in the chlor‐alkali industry suffer from a gradual loss of catalytic activity during storage, for example, during cell shut‐down. This deactivation process can be reversed by electrochemical cycling and the formation of atomic hydrogen. A deactivating layer forms upon electrode storage, as shown by in‐depth characterization of the formed surface species and intraporous electrode space and by the removal of the formed layer.