MnCo2O4 Nanofibers as Efficient Photo-electrocatalyst for Oxygen Evolution Reaction and Oxygen Reduction Reaction

Photoactive bimetal oxide catalysts towards oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) activities have not yet been comprehensively investigated. Herein, this work presents the MnCo2O4 nanofiber using as a photo-electrocatalyst for OER and ORR. After irradiation with visible light, the MnCo2O4 decreases ca. 17.1% and 15.4% in overpotential of OER and ORR, respectively, while the overpotential of the Co3O4 is reduced ca. 8.6% and 6.4% towards OER and ORR processes, respectively. These results suggest that MnCo2O4 can enhance OER/ORR performances with two-fold higher than Co3O4 under the light illumination. Due to the mixed valence states of Mn2+ and Mn3+ in its spinel structure, the MnCo2O4 has lower band gap energy (1.7 eV) than the Co3O4 nanofiber (2.0 eV). This narrower band gap can facilitate electron transfer from the valence band to the conduction band. Moreover, the photogenerated MnCo2O4* holes can accelerate the reaction with OH- and H2O which subsequently enhances OER performance.