One-dimensional hierarchical nanostructures of NiCo 2 O 4 , NiCo 2 S 4 and NiCo 2 Se 4 with superior electrocatalytic activities toward efficient oxygen evolution reaction

Oxygen evolution reaction (OER), a sluggish multistep process in electrochemical water splitting, is still a challenging issue to achieve with cheap, earth-abundant non-precious and non-polluting materials. In this work, three different electrocatalysts, specifically NiCo₂O₄, NiCo₂ S₄, and NiCo₂ Se_4, synthesized by simple hydrothermal process, show excellent OER activity. This report not only projects OER performances but also demonstrates a modified method for the transformation of NiCo₂O₄ to NiCo₂ S₄ and NiCo₂ Se₄ via sulfidation and selenization reactions. The well crystalline, porous nature of NiCo₂O₄, NiCo₂ S₄, and NiCo₂Se₄ electrocatalysts with one dimensional (1D) structural morphology affords overpotentials of 346 mV, 309 mV and 270 mV at current density of 10 mA cm^-2 in 1 M KOH. In particular, NiCo₂Se₄ exhibits a low overpotential as well as a smaller Tafel slope of 63 mV dec^-1, leading to robust stability in alkaline conditions. The abundant active sites, large mass and size of NiCo₂Se₄ enhances the performance of the OER. This type of selenide-based material with low toxicity is also an advantage for eco-friendly applications.