One-dimensional hierarchical nanostructures of NiCo <sub>2</sub> O <sub>4</sub> , NiCo <sub>2</sub> S <sub>4</sub> and NiCo <sub>2</sub> Se <sub>4</sub> with superior electrocatalytic activities toward efficient oxygen evolution reaction
Shrine Maria Nithya Jeghan, Gibaek Lee
Abstract
Abstract 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 NiCo 2 O 4 , NiCo 2 S 4 , and NiCo 2 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 NiCo 2 O 4 to NiCo 2 S 4 and NiCo 2 Se 4 via sulfidation and selenization reactions. The well crystalline, porous nature of NiCo 2 O 4 , NiCo 2 S 4 , and NiCo 2 Se 4 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, NiCo 2 Se 4 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 NiCo 2 Se 4 enhances the performance of the OER. This type of selenide-based material with low toxicity is also an advantage for eco-friendly applications.