Defect-induced FexNi1-xSe2 nanoparticles based electrocatalysts towards enhanced hydrogen and oxygen evolution reactions

Abstract

Transition metal selenides are regarded as promising materials for the production of clean energy through electrocatalytic water splitting. Creation of defects in these metal selenides is one of the prudent strategies to enrich the active sites which in turn enhances the electrocatalytic activity of these materials and makes them viable for broader applications. Herein, defect-induced, iron-doped nickel selenide nanoparticles were prepared for the first time and their electrocatalytic efficacy towards hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has been demonstrated. FexNi1-xSe2 nanoparticles (x = 0.25, 0.50, 0.75) were prepared using a facile hydrothermal method, in which defects were induced by annealing at 300 °C to obtain DI-FexNi1-xSe2. The structural and morphological investigations confirmed the size reduction and creation of defects after annealing, without any significant change in the crystal structure, which in turn is expected to promote the electrocatalytic activity. Accordingly, among all the materials investigated, DI-Fe0.25Ni0.75Se2 has shown the highest HER activity in 0.5 M H2SO4 at a lesser overpotential of 128 mV at 10 mA cm−2 and the Tafel slope was calculated to be 37.9 mV dec−1. Interestingly, the same material has displayed high performance towards OER in 1 M KOH with a lesser overpotential at 205 mV and a Tafel slope of 55.5 mV dec−1. Thus obtained electrocatalytic activity was much better than the reported nickel selenide based electrocatalysts. Further, the DI-Fe0.25Ni0.75Se2 electrocatalyst has demonstrated impressive stability in the acidic and alkaline medium during continuous electrolysis even up to 12 h.