Uniformly mesoporous NiO/NiFe2O4 biphasic nanorods as efficient oxygen evolving catalyst for water splitting

Development of efficient, stable and earth-abundant metal oxide electrocatalysts is crucial to improve the efficacy of water electrolysis for harvest and storage solar energy. In this work, we report the synthesis, structural characterization and electrocatalytic water oxidation performances of mesoporous NiO/NiFe2O4 nanorods. It is found that different calcination temperature of NiFe-based coordination polymer leads to various structural composites and completely preserves the original nanorod-like morphology of coordination polymer precursor. The nanorods obtained at 350 degrees C identified as NiO/NiFe2O4 have the largest surface area of 191.5 m(2) g(-1) with an average pore size of 6.4 nm. When used as oxygen evolving catalyst in water splitting, NiO/NiFe2O4 nanorods are found to exhibit the highest electrocatalytic water oxidation activity in basic media compared to the composites obtained at other temperatures, even much better than those of individual NiO or NiFe2O4 as well as commercial RuO2 and IrO2. The current density of 10 mA cm(-2) is met at an overpotential of 302 mV with a Tafel slope of 42 mV dec(-1). The excellent electrocatalytic performance could be attributed to the synergetic benefits of biphasic NiO/NiFe2O4 mesoporous structure and large surface area, which offer pathways for easy accessibility of electrolytes and fast mass/charge transportation. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.