TiO/Ti3O5-Decorated Electrospun Carbon Nanofibers as High-Performance Oxygen Reduction Reaction Electrocatalysts

Magne ' li phases TinO2n-1 (3 <= n <= 10) have been widely utilized in various electrochemical fields due to the adjustable phase composition and band structure. In addition, the excellent electrical conductivity and regularly distributed oxygen vacancies of TinO2n-1 phases lead to superior electrocatalytic activity. This work successfully synthesized different types of dual-phase TinO2n-1 nanoparticle-decorated electrospun carbon nanofibers (CNFs) to act as high-performance oxygen reduction reaction (ORR) electrocatalysts. Based on the precisely controlled calcination temperature and holding time, the combinations among two of TiO(T1), Ti2O3(T2), and Ti3O5(T3) dual-phase nano-particle-decorated CNF composite catalysts can be obtained after a one-step calcination process. The CNF/T1/T3 catalysts with an ideal 4-electron transfer path exhibit the best ORR catalytic activity with the onset and half-wave potential of 0.91 and 0.77 V, respectively. Compared with commercial Pt/C catalysts, such composite catalysts possessed better methanol tolerance and chemical stability with less than 20% relative current density attenuation after a 80,000 s-long cycle process. Furthermore, density functional theory (DFT) calculations suggest the different reaction energy barriers of ORR steps on the surface of different TinO2n-1 phases. Compared with the single-phase CNF/TinO2n-1 catalysts, the energy barrier of the rate-determining step can be reduced significantly through the diffusion of intermediate products, which proved the synergistic catalytic effect of the dual-phase TinO2n-1 nanoparticles.