Catalytic Reactivation of Industrial Oxygen Depolarized Cathodes by in situ Generation of Atomic Hydrogen

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.

The Key Role of Water Activity for the Operating Behavior and Dynamics of Oxygen Depolarized Cathodes

“…Although both set‐ups varied in the orientation of the ODC, no influence due to the hydrostatic pressure p ( h ) is expected, as the height of electrolyte level h was approx. 1 cm for both set‐ups, which leads to p ( h ) ≤ 150 Pa. A detailed documentation of the set‐up with the convective electrolyte flow is given in, and for the cell with the stagnant electrolyte in . In the latter set‐up, SECM was used to quantify the hydroxide activity under stationary operating conditions.…”