The efficiency of electrochemical water splitting is greatly hindered by the thermodynamic uphill reaction of oxygen evolution reaction (OER). Thus, it is important to synthesize an active OER electrocatalysts with abundant active sites, favorable conductivity and good durability. Herein, a facile reduction method using NaBH4 as readily available reductant has been developed to fabricate the reduced CoFe2O4 nanosheets (NS). The obtained reduced CoFe2O4 NS are rich in oxygen deficient sites, leading to more active sites as well as the enhanced conductivity than the pristine CoFe2O4 hollow nanosphere, which reaches the current density of 10 mA cm(-2) at the overpotential of 320 mV in 1 M KOH. Meanwhile, CoFe2O4 samples with three different morphology nanostructures including hollow nanospheres, bulk and nanoparticles have been provided to study the effect of different morphology on NaBH4 reduction efficiency. As expected, after NaBH4 reduction, CoFe2O4 hollow nanosphere with relatively higher surface area exhibits most obvious improvement for OER activity and also its corresponding reduced CoFe2O4 NS showed best OER performance than the reduced CoFe2O4 bulk as well as the reduced CoFe2O4 nanoparticles, implying the hollow nanospheres feature more accessible surface area than bulk and nanoparticles samples, thus greatly facilitate efficiency of NaBH4 reduction treatment. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.