Recovering activity of anodically challenged oxygen reduction electrocatalysts by means of reductive potential pulses

Abstract

The stability of electrocatalysts is of great importance to ensure their applicability, but stability is generally only considered for catalysts polarised to a constant potential or current density. This excludes stability evaluation under start stop conditions in a fuel cell or in reversible batteries in which the catalyst is alternately polarised to high opposite potentials. For example, the poor cyclability of metal air batteries is mainly due to the decrease in the oxygen reduction activity of electrocatalysts during the high applied potentials for the oxygen evolution reaction during battery charging. To investigate and at least partially mitigate the loss of electrocatalytic activity for the oxygen reduction reaction, we employed reductive pulses with the aim of restoring the catalytic activity of the active sites for the oxygen reduction reaction. Optimisation of the reductive pulse parameters makes it possible to substantially prolong the oxygen reduction activity of a Fe Nx doped carbon based oxygen reduction electrocatalys