Mn3O4@C Nanoparticles Supported on Porous Carbon as Bifunctional Oxygen Electrodes and their Electrocatalytic Mechanism

Abstract Mn 3 O 4 nanoparticles encapsulated inside carbon nanospheres supported on a carbon plate (Mn 3 O 4 @CS/CP) were designed, their bifunctional electrocatalytic performance for both, the oxygen evolution reaction (OER) at the anode and the oxygen reduction reaction (ORR) at the cathode were studied in alkaline solution. The prepared Mn 3 O 4 @CS/CP catalyst exhibits excellent electrocatalytic performance towards ORR, with less negative onset potential and long durability. Combining the results of in‐situ Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations, it is revealed that Mn 3 O 4 acts as active site for ORR to promote the transformation of OH* into OH − . In addition, Mn 3 O 4 @CS/CP possesses an excellent electrochemical OER performances with the lower overpotential along with prosper Tafel slope and robust durability. DFT calculations show the transformation from O* to OOH* is the rate determining step for OER, and Mn 3 O 4 @CS/CP shows the minimum barrier, indicating that graphene sheet on the outer of Mn 3 O 4 improves the transformation from O* to OOH*. The oxygen electrode activity parameter (potential difference between OER at current density of 10 mA/cm 2 and ORR at current density of −2 mA/cm 2 ) on Mn 3 O 4 @CS/CP is 0.72 V, which is superior to those of most bifunctional electrocatalysts reported to date, predicting a promising application in metal‐air batteries and fuel cells.