Enhanced bifunctional electrocatalytic activity of Ni-Co bimetallic chalcogenides for efficient water-splitting application

Because of a high global energy demand and challenging sustainability requirements, hydrogen has been promoted as a clean and green energy carrier allowing the potential replacement of nonrenewable fossil fuels. Hydrogen is a renewable energy carrier that does not contribute to CO2 emissions, and it holds the highest gravimetric energy density. It can be produced by the electrochemical splitting of water into hydrogen and oxygen molecules. Herein, we investigate the bifunctional activity of bimetallic oxide, sulfide, and selenide nanostructures in water electrolysis. Spinel-type, phase-pure NiCo2O4, NiCo2S4, and NiCo2Se4 with comparable morphological properties were synthesized by a hydrothermal method. The electrocatalytic characterization of NiCo2Se4 was found to demonstrate higher oxygen and hydrogen evolution reaction activities (245 mV and 122 mV @ 10 mA cm(-2), respectively) compared to those of NiCo2O4 and NiCo2S4. Furthermore, a lab-scale water-splitting system was fabricated to examine the bifunctional properties of bimetallic nanostructures. A NiCo2Se4-based water-splitting system was found to require a cell voltage of 1.58 V, which is lower than that required by NiCo2S4 (1.64 V)- and NiCo2O4 (1.75 V)-based systems. In summary, this study explores bimetallic NiCo2Se4 as an efficient electroactive material that can be employed in various electrochemical energy systems. (C) 2020 Elsevier B.V. All rights reserved.