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

Abstract

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.

RuO2 Catalysts for Electrocatalytic Oxygen Evolution in Acidic Media: Mechanism, Activity Promotion Strategy and Research Progress

“…Cation doping has been widely studied to improve the intrinsic activity of Ru oxides, and various metallic elements (e.g., Ni, Nd, Nb, W, Er, Li, Mo, ln) can greatly improve the OER activity of Ru-based electrocatalysts in acidic media. Doping does not transform the OER mechanism, and the enhanced activity primarily stems from the optimized binding energy of oxygen intermediates [ 20 , 49 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 ]. Sun et al synthesized Nb 0.1 Ru 0.9 O 2 by doping high-valence refractory metal niobium into ruthenium oxide, which promoted the electron transfer in the local structure of Ru-O-Nb and reduced the valence state of Ru sites and the covalency of Ru-O bond [ 21 ].…”