Controlled synthesis of tubular ferrite MFe2O4 (M = Fe, Co, Ni) microstructures with efficiently electrocatalytic activity for water splitting

Ferrite MFe2O4 (M = Fe, Co, Ni) tubular microstructures were successfully synthesized through a simple two-step strategy. The tubular FeOOH microstructures were first obtained by a heating reflux route. Then, tubular ferrite MFe2O4 (M = Fe, Co, Ni) microstructures were produced by a solvothermal method. The as-prepared products were characterized by the powder X-ray diffraction (XRD), the field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and EDS mapping. Experiments showed that as-obtained ferrite catalysts demanded the overpotentials of -201 similar to-359 mV or similar to 340-432 mV to afford the current density of -/+10 mA cm(-2) for hydrogen evolution reaction (HER) or oxygen evolution reaction (OER) with long-term durability for 50 h in 1.0 M KOH solution. Among them, NiFe2O4 tubular microstructures presented the best electrocatalytic activities for HER and OER due to the largest BET specific surface area, the highest electrochemical active surface area and the smallest chargetransfer resistance. Obviously, the present ferrite tubular microstructures have potential application as a bifunctional electrocatalyst for full water splitting. (C) 2019 Elsevier Ltd. All rights reserved.