Cobalt-Iron Oxide Nanoarrays Supported on Carbon Fiber Paper with High Stability for Electrochemical Oxygen Evolution at Large Current Densities

Here, we demonstrate that nonprecious CoFe-based oxide nanoarrays exhibit excellent electrocatalytic activity and superior stability for electrochemical oxygen evolution reaction (OER) at large current densities (>500 mA cm –2 ). Carbon fiber paper (CFP) with three-dimensional macroporous structure, excellent corrosion resistance, and high electrical properties is used as the support material to prevent surface passivation during the long-term process of OER. Through a facile method of hydrothermal synthesis and thermal treatment, vertically aligned arrays of spinel Co x Fe 3– x O 4 nanostructures are homogeneously grown on CFP. The morphology and the Fe-doping content of the CoFe oxide nanoarrays can be controlled by the Fe 3+ concentration in the precursor solution. The arrays of CoFe oxide nanosheets (NSs) grown on CFP (Co 2.3 Fe 0.7 O 4 -NSs/CFP) deliver lower Tafel slope (34.3 mV dec –1 ) than CoFe oxide nanowire (NW) arrays grown on CFP (Co 2.7 Fe 0.3 O 4 -NWs/CFP) in alkaline solution, owing to higher Fe-doping content and larger effective specific surface area. The Co 2.3 Fe 0.7 O 4 -NSs/CFP electrode exhibits excellent stability for OER at large current densities in alkaline solution. Moreover, the morphology and structure of CoFeO nanoarrays are well preserved after long-term testing, indicating the high stability for OER.