Preparation and catalytic studies of pyrrole-doped carbon black oxide cathode materials for oxygen reduction reactions

Oxygen reduction reaction (ORR) is an important cathode reaction for alkaline fuel and air-metal batteries. Because of the high cost and low stability of traditional Pt-based cathode materials for ORR, it is important to find an alternative cathode material of high performance and stability and low cost. Nitrogen-doped carbonaceous materials are currently of keen interest among those alternative oxygen cathode materials. The arrangement of carbon atoms in carbon black (CB) is similar to that of graphite, and it is wellknown that CB has a unique advantage over other carbon materials owing to its relatively low price and wide availability. Based on cheap carbon black, pyrrole-doped carbon black oxide (rCBO-Pyrrole) cathode materials were prepared using a facile synthesis method for this article, and their catalytic performances toward ORR were studied. The characterization of the catalysts was explored using a scanning electron microscope (SEM), a transmission electron microscope (TEM), ultraviolet-visible spectroscopy (UV-Vis), and Brunauer-Emmett-Teller (BET) specific surface area and X-ray photoelectron spectroscopy (XPS). The results of these analyses indicate that nitrogen is successfully doped in the rCBO-Pyrrole composite. BET results show that both rCBO and rCBO-Pyrrole have large specific surface areas, which increase significantly after pyrrole doping of carbon black. Further, the results of catalytic performances show that the rCBO-Pyrrole composite induces excellent catalytic activity toward ORR and exhibits the best performance after heat treatment at 700 ℃. In the electrolyte of KOH (1 mol·L^-1), the onset potential of rCBO-Pyrrole is 0. 9 V vs RHE, and the limit diffusion current density of this catalyst is 2. 6 m A·cm^-2. Moreover, the electron transfer number of ORR on rCBO-Pyrrole is higher than 3. 5, which indicates a preference for the four-electron reduction pathway. These characteristics and results demonstrate that this kind of material has broad potential applicability.