Pushing the limits of the layers: completely delaminated α-Ni(OH)2 – an enhanced electrocatalyst for the OER

Abstract

Two-dimensional materials are widely used as electrode materials in various electrochemical applications. Nickel hydroxide has shown great promise as a catalyst for water splitting, a key process for producing hydrogen and advancing sustainable energy technologies. The catalytic efficiency of nickel hydroxide nanostructures in splitting water into hydrogen and oxygen is attributed to its excellent electrochemical properties, such as high catalytic activity and stability. In our study, we have synthesized a special form of α-Ni(OH)₂ with completely delaminated hydroxide layers, by intercalating ions in between the positively charged layers of Ni(OH)_2−x. These positive charges are balanced by the intercalated anions. We have synthesized nickel hydroxide layers intercalated with molybdate and cobalt ions using a straightforward hydrothermal method, with a morphology resembling a coral reef. This material demonstrated lower overpotential values of 240 mV and 290 mV at 10 mA cm⁻² and 50 mA cm⁻², respectively, and maintained the catalytic activity for 100 hours without a large amount of degradation. Analyses using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), high-angle annular dark field imaging (HAADF), and X-ray photoelectron spectroscopy (XPS) confirmed that the α-Ni(OH)₂ layers are dual intercalated and exhibit a uniform distribution of electroactive species on the layered hydroxide.