Design and synthesis of carbon nanofibers decorated by dual-phase TinO2n-1 nanoparticles with synergistic catalytic effect as high performance oxygen reduction reaction catalysts

As a green pollution-free reaction, oxygen reduction reaction (ORR) plays a significant role in many energy storage and conversion devices. Although commercial Pt/C possesses the highest ORR activity (especially in acidic medium), the high cost, low stability and poor methanol tolerance making the development of non-platinum electrocatalysts with high performance especially important. Herein, we design and synthesize a carbon nanofiber decorated by Ti4O7/Ti3O5 dual-phase nanoparticles (CNF/T4/T3) as ORR catalysts with excellent activity. With the employment of electrospinning followed by precisely controlled calcination process, the composite catalysts with uniform fibrous morphology can be obtained. Such CNF/T4/T3 composite catalysts exhibited an improved electrochemical performance with onset and half-wave potential of 0.91 V and 0.78 V respectively in alkaline solution. By comparing the catalytic performance with the pure T4 or T3 phase decorated on the same carbon nanofiber, it is found that the mixture of the two titanium sub-oxide phases can optimize the onset potential and limited current density at the same time. Density functional theory calculations suggest that different steps of ORR take place on T3 and T4 successively, which is the main reason of the excellent ORR performance for the dual-phase structure. This work provided a novel designing concept for the functional electrocatalysts using electrospinning technique for the application of energy storage and conversion.