Oxygen Reduction Properties On Cathode Of Carbon Nanofibers Functional Groups As Catalyst Or Pt Catalyst Support

As a novel kind of carbon material with special electrical properties, adjustability of microstructures and larger surface area, carbon nanofibers (CNFs) has attracted intensity attention as catalyst or caltalyst support in fuel cell. According to the difference of the microstructures, CNFs can be divided into tubular CNFs (T-CNF), fish-bone CNFs (F-CNF) and platelet CNFs (P-CNF).In this paper, we have studied the effect of CNFs surface microstructures and functional groups on oxygen reduction reaction (ORR) by using CNFs as catalyst or catalyst support to load Pt nanoparticles. And now the main rusults we obtained are as follows:(1) The CNFs tip actom is more active than the sidewall actom towards ORR, and the tip actom is more conducive to the loading of Pt nanoparticle, so the Pt/F-CNF catalyst exhibits higher ORR activity than Pt/T-CNF catalyst.(2) Carboxyl groups (CNF-OX), Carbonyl groups (CNF-CO), hydroxyl groups (CNF-OH) and nitrogen-containing groups (CNF-ON) were introduced onto F-CNF surface by different treatments. Cyclic voltammetric results show that CNF-ON exhibits the highest ORR activity, followed by CNF-OX, CNF-CO, CNF-OH and CNF-P. RDE results showed that ORR on CNF-ON/GC electrode was almost entirely by the four-electron reduction pathway, the ORR on CNF-OX/GC, CNF-CO/GC and CNF-OH/GC electrodes proceed from a two-electron reduction pathway at low potentials to a gradual four-electron reduction pathway at more negative potentials, while a two-electron reduction pathway within the whole range of potential studied was found on the untreated carbon nanofiber (CNF-P/GC) electrode.(3) Using CNF-OX and CNF-OH as catalyst support, respectively. High resolution transmission electron microscopy (HRTEM) characterization showed that the Pt nanoparticles were highly dispersed on the two modified CNFs supports, and the Pt nanoparticles supported on the CNF-OH exhibited a smaller mean particle size and a more uniform particle size distribution. RDE analyses revealed that compared with Pt/CNF-OX, Pt/CNF-OH exhibits a better activity towards ORR, and this may be attributed to the smaller particle size and the better dispersion of Pt nanoparticles on CNF-OH support.