Hierarchical CoWO 4 /Ni x Fe y S microspheres bearing crystalline-amorphous interface as a multifunctional platform for outperformed water splitting and sensitive hydrazine sensing.

Highly efficient and multifunctional electrocatalysts are of high value in energy transformation and electrochemical sensing. Herein, hierarchically architectured cobalt tungstate/nickel iron sulfide (CoWO4 /Nix Fey S) microspheres with a crystalline-amorphous interface have been prepared on bimetallic substrate of nickel-iron foam (NIF) by a two-step hydrothermal method. Electrochemical characterization shows that CoWO4 /Nix Fey S microspheres can boost the electrocatalytic activity effectively through the synergistic effect on the crystalline-amorphous interface. When the CoWO4 /Nix Fey S is applied as the electrocatalysts for oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), the overpotentials at a high current density of 500 mA cm-2 are only 322.8 mV and 306.5 mV, respectively. The overall water splitting device composed of CoWO4 /Nix Fey S/NIF couple only needs a cell voltage of 1.80 V to reach a current density of 100 mA cm-2 , and 2.19 V to reach 500 mA cm-2 . The CoWO4 /Nix Fey S/NIF can be also utilized as an effective electrochemical platform for the sensing of toxic hydrazine in a wide range from 50 μM to 17.3 mM, with a detection limit of 46.4 μM. All these results display that the CoWO4 /Nix Fey S/NIF can be a high-performance multifunctional material for energy transformation and environmental pollutant monitoring.