Bifunctional NiCo2Se4 and CoNi2Se4 nanostructures: Efficient electrodes for battery-type supercapacitors and electrocatalysts for the oxygen evolution reaction

Abstract

We report the fabrication of bimetallic NiCo2Se4 and CoNi2Se4 nanostructures on nickel-foam (Ni-foam) substrates via a potentiostatic-deposition method by adjusting the molar ratio of Ni and Co metals. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses show that burl-like clusters with characteristic fluffy NiCo2Se4 and flake-like CoNi2Se4 hierarchical structures were deposited on the Ni-foam substrates. When used as battery-type electrodes in supercapacitors, both NiCo2Se4 and CoNi2Se4 electrodes exhibited outstanding capacity and good electrochemical properties. The CoNi2Se4 electrode delivered excellent capacity and cycling stability (602Cg–1 at 1Ag–1 and 98.30% retention after 5000 cycles at 40Ag–1) when compared to the NiCo2Se4 electrode (353Cg–1 at 1Ag–1 and 96.83% retention after 5000 cycles at 40Ag–1). Furthermore, as-deposited NiCo2Se4 and CoNi2Se4 hierarchical structures were employed as efficient electrocatalysts for water oxidation in alkaline solutions. NiCo2Se4 and CoNi2Se4 electrocatalysts showed low overpotentials of 257 and 244mV in a 1.0M KOH aqueous solution, respectively. The electrocatalysts also exhibited prolonged stability (NiCo2Se4 and CoNi2Se4 maintained currents of 95.6% and 97.5%, respectively, over 10h), which makes them comparable to well-known Ni and Co-based catalysts. Collectively, the as-deposited NiCo2Se4 and CoNi2Se4 are the most efficient bifunctional electrodes and electrocatalysts for application in battery-type supercapacitors and the oxygen evolution reaction, respectively, and can potentially be applied for energy conversion and storage processes.