Efficient electrocatalytic nanocomposites of carbon nanotubes decorated with nickel selenides for urea oxidation reaction

In this study, carbon nanotubes (CNTs) coated with various phases of nanostructured nickel selenides were successfully synthesized with a simple and effective technique. These nanocomposites were then used as highly effective electrocatalysts for the urea oxidation reaction (UOR). The strategy involved depositing CNTs onto stainless steel (SS) foam using chemical vapor deposition, followed by pulse-reversal electrodeposition of nickel selenides in a layer-by-layer fabrication process. Different phases of nanostructured nickel selenides, such as NiSe2, NiSe2/Ni0.85Se, and Ni0.85Se, were successfully deposited on the surface of CNTs by controlling the reversal potential. Among all the different nanocomposites, the Ni0.85Se@CNTs-SS electrode exhibited the best electrocatalytic activity towards UOR. It required only a low overpotential, about 158 mV, to reach a benchmarking current density of 10 mA cm- 2, and showed a low Tafel slope value of 85 mV dec- 1. Additionally, the results of the prolonged stability study for 24 h confirmed the remarkable electrochemical stability of the Ni0.85Se@CNTs-SS electrode. After conducting stability studies, the overpotential shifted from 158 mV to 107 mV. This shift is due to the activation of the electrocatalyst during the stability test. The excellent electrocatalytic activity observed after the stability test is attributed to the presence of hydroxide and oxyhydroxide phases, which are remarkably active phases. This is the first-ever report where the Ni0.85Se@CNTs-SS nanocomposite electrode is shown to hold great potential as an effective electrocatalyst for UOR, which is an important step toward the design of a future electrocatalyst for UOR.