Enhancing the stability of cobalt spinel oxide towards sustainable oxygen evolution in acid

Polymer electrolyte membrane water electrolysis is more efficient than its alkaline counterpart, but its implementation, in part, hinges on developing Earth-abundant catalysts that are active and stable for the oxygen evolution reaction in acid. Now, it is shown that incorporating Mn into Co3O4 substantially extends the catalyst lifetime in acidic electrolyte while maintaining the activity. Active and stable electrocatalysts for the oxygen evolution reaction are required to produce hydrogen from water using renewable electricity. Here we report that incorporating Mn into the spinel lattice of Co3O4 can extend the catalyst lifetime in acid by two orders of magnitude while maintaining the activity. The activation barrier of the obtained spinel Co2MnO4 is comparable to that of state-of-the-art iridium oxides, most probably due to the ideal binding energies of the oxygen evolution reaction intermediates, as shown using density functional theory calculations. The calculations also show that the thermodynamic landscape of Co2MnO4 suppresses dissolution, which results in a lifetime of over 2 months (1,500 hours) at 200 mA cm(geo)(-2) at pH 1. As the lifetimes of other 3d metal oxygen evolution catalysts are in the order of days and weeks, despite current densities being lower by an order of magnitude, our results are an important step towards the realization of noble-metal-free water electrolysers.