Novel Co1-xS/C-3 supported on N-doped ketjen black as an efficient electrocatalyst for oxygen reduction reaction in alkaline media

Abstract

Highly efficient and low-cost catalysts are greatly desirable for oxygen reduction reaction (ORR) in the cathode of metal-air batteries. Herein, a novel Co1-xS/C-3/N-KB catalyst is prepared by a facile process with cheap raw materials. The electrocatalytic performance of Co1-xS/C-3/N-KB for ORR are investigated systematically. As results, Co1-xS/C-3/N-KB exhibits a half-wave potential of 0.72 V and a limiting current density of 6.0 mA·cm−2, comparable to the commercial Pt/C. Moreover, by means of Koutecky–Levich and RRDE techniques, the catalyst is confirmed to catalyze ORR at a four-electron pathway. Besides, chronoamperometric studies indicate a better catalytic stability of Co1-xS/C-3/N-KB than that of Pt/C with the current density retention rates of 93.4% and 88.3%, respectively. In addition, during the accelerated durability test, Co1-xS/C-3/N-KB shows only 11.5 mV negative shift of half-wave potential after 5000 cycles, even better than Pt/C (34.6 mV negative shift). When used as cathode catalyst for primary Al-air battery, the Co1-xS/C-3/N-KB catalyst exhibited excellent discharge voltage and better stability than Pt/C. The excellent ORR catalytic activity and stability of Co1-xS/C-3/N-KB can be due to the synergistic effect between the Co1-xS/C active sites and the N-KB support, which is not only beneficial to oxygen adsorption but also promotes efficient electron transfer, thus facilitating the oxygen reduction process. Besides, the coated/doped carbon and doped nitrogen in Co1-xS/C particles also have certain contribution, enhancing the electronic conductivity and catalytic stability, therefore facilitating the electronic transfer inside Co1-xS/C active particles during the oxygen reduction process.