Self-Supporting Mn-RuO₂ Nanoarrays for Stable Oxygen Evolution Reaction in Acid

Currently, the process of an acidic oxygen evolution reaction (OER) necessitates the use of Iridium dioxygen (IrO₂), which is both expensive and incredibly scarce on Earth. Ruthenium dioxygen (RuO₂) offers high activity for acidic OERs and presents a potential substitution for IrO₂. Nevertheless, its practical application is hindered by its relatively poor stability. In this study, we have developed Mn-doped RuO₂ (Mn-RuO₂) nanoarrays that are anchored on a titanium (Ti) mesh utilizing a two-step methodology involving the preparation of MnO₂ nanoarrays followed by a subsequent Ru exchange and annealing process. By precisely optimizing the annealing temperature, we have managed to attain a remarkably low overpotential of 217 mV at 10 mA cm^-2 in a 0.5 M H₂SO₄ solution. The enhanced catalytic activity of our Mn-RuO₂ nanoarrays can be attributed to the electronic modification brought about by the high exposure of active sites, Mn dopant, efficient mass transfer, as well as the efficient transfer of electrons between the Ti mesh and the catalyst arrays. Furthermore, these self-supported Mn-RuO₂ nanoarrays demonstrated excellent long-term stability throughout a chronoamperometry test lasting for 100 h, with no discernible changes observed in the Ru chemical states.