Bifunctional Electrodeposited 3D NiCoSe2/Nickle Foam Electrocatalysts for Its Applications in Enhanced Oxygen Evolution Reaction and for Hydrazine Oxidation

The development of stable and efficient oxygen evolutional electrocatalysts is fundamental to the production of hydrogen by water electrolysis. However, so far the majority of electrocatalysts require a substantial overpotential (eta) (approximately >250 mV) to catalyze the bottleneck oxygen evolution reaction (OER). To overcome this large overpotential for OER, herein we report the growth of nickel-cobalt-selenide (NiCoSe2) nanosheets over 3D nickel foam (NF) via a facile and scalable electrodeposition method. The resulting 3D NiCoSe2/NF hybrid electrode requires an overpotential of merely 183 mV to reach the current density (J) of 10 mA cm(-2). To the best of our knowledge, this is the lowest eta value reported so far for any earth-abundant material-based OER electrocatalyst to attain the same current density. Moreover, a significant reduction in Tafel slope (88 mV dec(-1)) is observed between bare NF and NiCoSe2/NF. Hence, as a result, the 3D hybrid NiCoSe2/NF OER electrode outperforms the previously reported electrocatalysts including the expensive state-of-the-art OER electrocatalysts like RuO2 and IrO2. Such enhancement in the OER catalytic efficiency of NiCoSe2 nanosheets over NF can be attributed to its enormous electrochemical active surface area (ECSA) (108 cm(2)), large roughness factor (270), highly conductive NF substrate, and the presence of multiple catalytically active OER species (NiOOH and CoOOH) on its surface. In addition, 3D hybrid NiCoSe2/NF electrocatalyst was tested for hydrazine oxidation for its bifunctional utilization. Much lower onset potential values (-0.7 V vs SCE) and high current densities (>200 mA cm(-2)) are observed for 3D hybrid NiCoSe2/NF when benchmarked against bare NF (-0.4 V and <50 mA cm(-2)). Furthermore, 3D hybrid NiCoSe2/NF OER electrode shows excellent stability of 50 h for continuous OER in strongly alkaline solutions while maintaining its enormous ECSA, chemical composition, and structural morphology. The excellent bifunctional electrocatalytic activity, long-term stability, and facile preparation method enable NiCoSe2/NF hybrid electrode to be a viable candidate for its widespread use in various water-splitting technologies.