One-dimensional hierarchical nanostructures of NiCo2O4, NiCo2S4 and NiCo2Se4 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 Se4, 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.