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

We investigated the electrocatalytic properties of Ir/β‐MnO2, with 4.2–5.6 atomic % (at %) iridium. The Ir/β‐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 °C. The Ir/β‐MnO2 (SA) was nano‐sized based on scanning and transmission electron microscopy (SEM and TEM). Using linear sweep voltammetry (LSV), 5.6 at % Ir/β‐MnO2 (SA) exhibited an overpotential ( η) ${\eta ){\rm \ }}$ of 327±5 mV for the oxygen evolution reaction (OER), at 10 mA cm-2 ${\hskip0.17em{{\rm c}{\rm m}}^{-2}}$ in 0.5 M H2SO4 electrolyte. At 10 mA cm-2 ${{{\rm c}{\rm m}}^{-2}}$ the Ir/β‐MnO2 (SA) catalyzed the OER for 72 h at an η ${\eta }$ 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 η of 420±7 for the OER, but after 20 h of operation at 10 mA cm-2 ${{{\rm c}{\rm m}}^{-2}}$ there was a steep rise in potential (>550 mV) and 12 % loss in Ir. The enhanced activity and stability of Ir/β‐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. Surfactant‐Assisted (SA) Ir/β‐MnO2 shows excellent OER stability compared to Ir/R‐MnO2 and IrO2 due to uniform distribution of Ir−O−Mn structural motif and thin‐sheet like morphologies with nano‐dimensioned particles. Catalyst degradation through Ir‐loss is minimal over three days of water splitting while Ir/R‐MnO2 and IrO2 are ineffective within ~24 hours.