Effects of Ir-Incorporation and Nanostructuring in β-MnO2 for an Enhanced Electrocatalytic Oxygen Evolution Reaction

We investigated the electrocatalytic properties of Ir/beta-MnO2, with 4.2-5.6 atomic % (at %) iridium. The Ir/beta-MnO2 was synthesized by heating Ir/R-MnO2-formed via a surfactant-assisted (SA) method using KMnO4, IrCl3.H2O, and sodium dodecyl sulfate (SDS)-to 400 degrees C. The Ir/beta-MnO2 (SA) was nano-sized based on scanning and transmission electron microscopy (SEM and TEM). Using linear sweep voltammetry (LSV), 5.6 at % Ir/beta-MnO2 (SA) exhibited an overpotential ( eta) of 327 +/- 5 mV for the oxygen evolution reaction (OER), at 10 mA cm(-2) in 0.5 M H2SO4 electrolyte. At 10 mA cm(-2) the Ir/beta-MnO2 (SA) catalyzed the OER for 72 h at an eta of 534 mV. During this time there was a 12 % loss in Mn and 8 % loss in Ir from the structure. An IrO2 catalyst exhibited an initial eta of 420 +/- 7 for the OER, but after 20 h of operation at 10 mA cm(-2) there was a steep rise in potential (>550 mV) and 12 % loss in Ir. The enhanced activity and stability of Ir/beta-MnO2 (SA) is attributed to the incorporation of Ir into the MnO2 lattice during synthesis and the formation of nano-sized particles using the SA method.