Stabilizing Reconstructed Ir-O Motifs by Mn Doping for Enhanced Acidic Water Oxidation

초록

Reconstructed Ir-O motifs are the origin of the high catalytic activity of mixed-metal oxides for acidic water oxidation but suffer from severe degradation caused by lattice oxygen participation in the process. Herein, we incorporate acid corrosion-resistant Mn into orthorhombic La3IrO7 (La3Ir1-x Mn x O7), promoting surface reconstruction to produce an asymmetric Mn-O-Ir local structure that is stable and highly active for the acidic oxygen evolution reaction (OER). The catalyst with 23.15 wt % Ir content exhibits significantly enhanced stability with no obvious degradation after operation for 175 h and outstanding mass activity of 284.7 A gIr -1 at 1.57 V vs RHE, which is 4.8-fold higher than that of commercial IrO2. Experimental and theoretical research revealed that Mn doping-induced charge accumulation around the Ir center and optimized orbital energy levels of Ir and coordinated O inhibit the lattice oxygen mechanism (LOM) but promote the adsorbate evolution mechanism (AEM), thus enhancing catalytic stability. Furthermore, the strong electronic coupling between Mn and Ir optimizes the adsorption free energy of the *OOH intermediate as the rate-determining step of the OER, thus improving its activity and accelerating the overall kinetics. This work offers a novel strategy for stabilizing in situ reconstructed Ir-O highly active motifs via the integration of an acid corrosion-resistant metal element into low-iridium mixed oxides.

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