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

Abstract

Magnéli phases Ti n O2n–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 Ti n O2n–1 phases lead to superior electrocatalytic activity. This work successfully synthesized different types of dual-phase Ti n O2n–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 Ti n O2n–1 phases. Compared with the single-phase CNF/Ti n O2n–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 Ti n O2n–1 nanoparticles.

Analysis of the Inhomogeneous Growth of Sputtered Black TiO2 Thin Films

“…Conversely, for n > 4, substantial changes in the crystal structures lead to notable shifts in the catalytic properties. 22 , 23 Raman studies of Ti 2 O 3 , Ti 3 O 5 , and Ti 4 O 7 show a variety of peaks for each phase. 24 − 26 The congruence in peak positions between these studies and the broad peaks observed in Figure 6 supports the presence of these three Magneli phases in the sample investigated.…”

“…Magneli phases with n ≤ 4 prove to be promising catalysts, exhibiting enhanced catalytic activity, remarkable stability, and resistance to corrosion. Conversely, for n > 4, substantial changes in the crystal structures lead to notable shifts in the catalytic properties. , Raman studies of Ti 2 O 3 , Ti 3 O 5 , and Ti 4 O 7 show a variety of peaks for each phase. − The congruence in peak positions between these studies and the broad peaks observed in Figure supports the presence of these three Magneli phases in the sample investigated. However, the absence of an identifiable dominant phase necessitates the assumption of a composite mixture consisting of three distinct phases.…”