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 S-4, and NiCo2 Se-4,Se- 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 S-4 and NiCo2 Se-4 via sulfidation and selenization reactions. The well crystalline, porous nature of NiCo2O4, NiCo2 S-4, 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.