Manipulating electronic delocalization of Mn3O4 by manganese defects for oxygen reduction reaction

Manganese-based oxides are promising in electrocatalytic oxygen reduction reaction, but the activity and conductivity need further improvement. Herein manganese defected Mn3O4 was fabricated by solvothermal synthesis of manganese glycerate and then thermal calcination. The experimental and computational results reveal that manganese defects in Mn3O4 modify the electronic structure to improve conductivity and electronic delocalization, which helps to expose more surface Mn3+ as major active site, thereby facilitating O2 activation and OH* desorption, and reducing the Gibbs free energy variation in the rate-limiting step of ORR. Accordingly, the onset potential, half-wave potential and limiting current density of manganese defected Mn3O4 are 0.87 V, 0.65 V and 5.0 mA cm-2, better than that of normal Mn3O4 (0.77 V, 0.62 V and 2.6 mA cm-2). This work provides an effective approach to tune the defects and electronic structures of Mn3O4 for better electrochemical activity.