One-pot synthesis of monodispersed porous CoFe2O4 nanospheres on graphene as an efficient electrocatalyst for oxygen reduction and evolution reactionsElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ra23306b

• Main Authors: Yan, Wenning, Cao, Xuecheng, Ke, Ke, Tian, Jinghua, Jin, Chao, Yang, Ruizhi
• Format: Journal Article
• Published: 22.12.2015
• ISSN: 2046-2069
• DOI: 10.1039/c5ra23306b

Monodispersed porous spinel-type cobalt ferrite oxide (CoFe 2 O 4 ) nanospheres (CFO-ns) directly grown on reduced graphene oxide (rGO) sheets are fabricated by a one-pot solvothermal method. With this special structure of CFO-ns and the covalent coupling between CFO-ns and rGO in the CFO-ns/rGO hybrid, more active sites are exposed and the transport of O 2 and electrolyte is faciliated when the CFO-ns/rGO hybrid is employed as an electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The CFO-ns/rGO hybrid demonstrates high catalytic activity for both the ORR and OER. It shows a more positive onset potential of −0.11 V ( vs. Ag/AgCl) for the ORR, which is 50 mV higher than that of CFO-ns + rGO physical mixture (−0.16 V). Meanwhile, the onset potential of CFO-ns/rGO hybrid (0.56 V) for the OER is 40 mV lower than that of CFO-ns + rGO mixture (0.60 V). The high activity of the CFO-ns/rGO hybrid is attributed to the special structure of CFO-ns, the covalent coupling between CFO-ns and rGO as well as the suppressed agglomeration of CFO-ns and restacking of rGO in the hybrid. Moreover, the covalent coupling between CFO-ns and rGO endows the hybrid with excellent electrochemical stabilities for both the ORR and OER. Monodispersed porous CoFe 2 O 4 nanospheres grown on graphene with high ORR/OER activities are fabricated by a simple one-pot solvothermal method.