Oxygen reduction electrocatalysts based on spatially confined cobalt monoxide nanocrystals on holey N-doped carbon nanowires: the enlarged interfacial area for performance improvement

Abstract

Due to the high cost of Pt-based materials used in the electrocatalysis of the oxygen reduction reaction (ORR), an alternative composed of non-precious metals is highly desirable. Herein a hybrid with cobalt monoxide nanocrystals spatially confined in holey N-doped carbon nanowires (CoO/NCWs) was synthesized via metal oxide assisted surface pitting of chemical vapor deposited carbon nitrogen nanowires and colloidal assembly. The catalyst consists of a Co²⁺ enriched surface and delivers a remarkably higher ORR electrocatalytic activity and stability than its surface smooth N-doped carbon nanotube supported counterpart, with a kinetically limited current density (30.3 mA cm⁻² at 0.7 V) nearly three times that of the latter. It also outperformed the commercial Pt/C catalyst. As characterized by cyclic voltammetry and XPS, the enlarged interfacial area by spatially confined hybridization is believed to be responsible for the improved ORR performance, which might create more active catalytic sites for the ORR. We propose that in-depth consideration of interfacial construction is essential when designing carbon supported metal oxide catalysts for the ORR in alkaline media.