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

Magnéli 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 nanoparticle-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.