Hierarchical construction of 3D binder-free NiMoO4/CoFe2O4/NF arrays to enhance water splitting and charge-storage efficiency

Developing inexpensive, highly active, robust bi-functional electrocatalysts for energy conversion and storage technology remains a vital challenge. Herein, we hierarchically constructed 3D binder-free NiMoO4/CoFe2O4/NF heterostructure material via an effective and facile two-step hydrothermal process. The strong electronic coupling among NiMoO4 and CoFe2O4 counterparts alternates the charge environment at the NiMoO4/CoFe2O4 interface, which builds the highway for a rapid and continuous charge transfer process. According to the surface characterization data, the 3D NiMoO4/CoFe2O4/NF surface possesses numerous multivalent active sites and affords robust structural and chemical stability to the electrode material. Benefiting from the hierarchical morphological reconstruction and synergistic effect between two functional materials of NiMoO4/CoFe2O4/NF heterostructure attained excellent over potential values of 88 mV and 249 mV with minimal Tafel slope value of 73 mV dec(-1), 84 mV dec(-1) for HER and OER respectively. For overall water splitting, experimental results demonstrated splendid stability over 50 h with a small cell voltage of 1.56 V at a current density of 10 mA cm(-2) in a 1 M KOH alkaline electrolyzer. Furthermore, its specific capacitance (CS) reached 811C g(-1) at 1 A/g and retained 85.5 % cycling stability after 5000 cycles at a current density of 5 A/g in a 6 M KOH electrolyte medium. This bi-functional hierarchical NiMoO4/CoFe2O4/NF heterostructured assembly will render outstanding electrocatalytic activity for future sustainable energy conversion and storage systems.