Three-dimensional self-supporting catalyst with NiFe alloy/oxyhydroxide supported on high-surface cobalt hydroxide nanosheet array for overall water splitting.

The development of available dual-function electrocatalysts is of great significance to the effective storage of excess electricity. Here, we obtained a three-dimensional Co(OH)2 nanosheet with high surface area on nickel foam (Co(OH)2/NF) via conventional hydrothermal. NiFe-coated Co(OH)2 nanosheet array (NiFe@Co(OH)2 NSAs/NF) was further constructed by electrodeposition for water splitting. By optimizing and regulating the deposition time, NiFe@Co(OH)2 NSAs/NF with a deposition time of 500 s (NiFe-500@Co(OH)2 NSAs/NF) only needs 98 mV of overpotential and can be stabilized for 100 h for hydrogen evolution at 10 mA cm-2 due to the rich density active components for NiFe alloy/oxyhydroxide layer and interaction with Co(OH)2 nanosheets. Thanks to the excellent 3D nanosheet array structure and the close integration between Co(OH)2 and the upper layer NiFe, NiFe@Co(OH)2 NSAs/NF with a deposition time of 200 s (NiFe-200@Co(OH)2 NSAs/NF) can provide 10 mA cm-2 with only 204 mV and maintain constant catalysis within 100 h. Therefore, the constructed NiFe@Co(OH)2 NSAs/NF (500||200) double-electrode cell for water splitting requires only 1.58 V drive potential and can maintain 24 h durability at 10 mA cm-2. The design of the catalyst opens up new ideas for the large-scale application of transition metals in water splitting.