OMS-2 nanorods filled with Co-ion in the tunnels as efficient electron conduits and regulatory substance for oxygen reduction

Abstract

Co-filled OMS-2 nanorods (Co-OMS-2) of different concentrations are synthesized by a simple hydrothermal reaction. Electrocatalytic test results indicate that Co-OMS-2 has excellent catalytic activity (Vonset: 0.905 V, Vhalf: 0.806 V vs. RHE), rapid reaction kinetics, and favorable stability. The obvious improvement in catalytic behavior correlates with the enhancement of conductivity and oxygen adsorption capacity studied by specific experiments. On the one hand, ions fill the tunnels as efficient electron conduits to accelerate the electron transfer and interconversion of Mn3+/ Mn4+ couple enhance intrinsic conductivity of OMS-2. On the other hand, ions in the tunnels act as regulatory substances to regulate the oxidation state requirements and coordination geometry of MnO6 octahedron, which is helpful to stabilize Mn3+ and enhance O2 adsorption. It is essential to understand the mechanisms that regulate the oxygen reduction activity of manganese oxides by filling the metal cation. And the roles of Co-ion in the tunnels of OMS-2 for oxygen reduction reaction (ORR) were studied in depth. All the experimental studies are confirmed by density functional theory (DFT) computations. This work shows for the first time there is an explicit correlation between OMS-2 and tunnel cation for the ORR in alkaline medium.