Bifunctional Electrodeposited 3D NiCoSe 2 /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 (η) (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 (NiCoSe 2 ) nanosheets over 3D nickel foam (NF) via a facile and scalable electrodeposition method. The resulting 3D NiCoSe 2 /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 η 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 NiCoSe 2 /NF. Hence, as a result, the 3D hybrid NiCoSe 2 /NF OER electrode outperforms the previously reported electrocatalysts including the expensive state-of-the-art OER electrocatalysts like RuO 2 and IrO 2 . Such enhancement in the OER catalytic efficiency of NiCoSe 2 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 NiCoSe 2 /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 NiCoSe 2 /NF when benchmarked against bare NF (−0.4 V and <50 mA cm –2 ). Furthermore, 3D hybrid NiCoSe 2 /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 NiCoSe 2 /NF hybrid electrode to be a viable candidate for its widespread use in various water-splitting technologies.