Spinel oxides wrapped on electrospun carbon nanofibers: Superior electrocatalysts boosted by enhanced conductivity and rich oxygen vacancies

Spinel oxides have been considered as promising precious metal-free catalysts for oxygen reduction reaction (ORR). However, the poor intrinsic conductivity and moderate electrocatalytic performance hinder their practical applications. Hence, various strategies have been explored and reported in addressing the issues. Herein, an elaborate approach for enhancing the ORR performance of spinel NiCo2O4 is proposed, by combining the decoration of NiCo2O4 nanoparticles on electrospun carbon nanofibers and defect engineering with rich oxygen vacancies on NiCo2O4 nanoparticles through a facilely controlling on calcination circumstance, which could not only increase more active sites and improve the intrinsic catalytic activity, but also render an excellent stability for long-term operation. Thus, the as-prepared hybrid exhibits significantly improved ORR electrocatalytic performance, including a high limited current density of −5.8 mA cm−2, a positively shifting of the onset potential at 0.88 V and half-wave potential at 0.76 V (vs. RHE). The performance of rechargeable Zn-air battery based on the as-prepared catalyst surpasses the one based on Pt/C catalyst significantly. This work can be also applied to other metal oxides based electrocatalysts, and then provided an avenue for the realization of metal-air batteries and fuel cells with high efficient and cost-effective.