Reusable water oxidation catalyst with dual active center for enhanced water oxidation: Iridium oxide nanoparticles immobilized on monodisperse-porous Mn5O8 microspheres

A reusable catalyst with dual active center for chemical water oxidation is synthesized for the first time by immobilization of iridium oxide nanoparticles (IrO2 NPs) on monodisperseporous manganese oxide microspheres acting both catalytic active center and support. Individual catalytic activity of manganese oxide microspheres is explained by multiple oxidation states of manganese which are capable of forming oxidative oxygen species. Monodisperse-porous microspheres in the form of Mn5O8, MnO2 and Mn2O3 are used for synthesis of different catalysts and the highest activity in water oxidation is observed with the catalyst synthesized using Mn5O8 microspheres. The catalytic activity is correlated with the total Mn(II) and Mn(III) percentage of manganese oxide type selected for composite catalyst. The oxygen evolution up to 244 mmol is achieved in 30 min with the catalyst synthesized using Mn5O8 microspheres. Maximum TON and TOF numbers are obtained as 298 and 557 h(-1) with excellent reusability. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

A reusable catalyst with dual active center was synthesized for the first time, using iridium oxide nanoparticles immobilized on monodisperse porous manganese oxide microspheres. The catalyst showed maximum activity in water oxidation when synthesized with Mn5O8 microspheres, and the catalytic activity was correlated with the oxidation states of manganese oxide. Oxygen evolution up to 244 mmol was achieved in 30 min, with maximum TON and TOF numbers obtained as 298 and 557 h(-1) respectively, demonstrating excellent reusability.