Controlling Stability and Selectivity in the Competing Chlorine and Oxygen Evolution Reaction over Transition Metal Oxide Electrodes

Abstract Chlor‐alkali electrolysis is a large‐scale industrial process, where the evolution of gaseous chlorine (chlorine evolution reaction, CER) at the anode is accompanied by a selectivity problem as the evolution of gaseous oxygen (oxygen evolution reaction, OER) constitutes an undesirable side reaction, which diminishes chlorine selectivity. The active component in the anode material is RuO 2 with the (110) facet as most stable surface termination, for which the elementary reaction steps on an atomic scale of the competing CER and OER are already resolved. Here, the selectivity issue and the stability range of a RuO 2 (110) electrode are explored under CER/OER conditions by combining the kinetic description with surface Pourbaix diagrams and linear scaling relationships. These investigations directly merge into a advanced material screening approach, indicating that the free energy difference between the limiting OOH (OER) and OCl (CER) adsorbate is reconciled as a measure for stability and CER selectivity. This finding supports computational researchers within their search of improved electrode materials based on transition metal oxides for electrocatalytic chlorine formation.