Optimised synthesis of Ni-Co hydroxide nanosheets: Effects on structural and electrochemical properties

Transition metal hydroxides exhibit significant potential as electrocatalysts, with their structural and electrochemical properties being highly dependent on the cation precursors. Metal hydroxides composed of two or more cations improve the structural and electrochemical properties by synergistically combining the advantages of metal hydroxides composed of cations of a single element. We synthesized Ni-Co hydroxide nanosheets at an air-water interface using a surfactant-assisted method and optimised the synthesis conditions by varying the component ratios. The synthesized Ni-Co hydroxide nanosheets exhibited various shapes depending on the Ni:Co ratio, transforming from hexagonal to triangular as the Co ratio increased. All nanosheets had an ultrathin thickness of less than 5 nm. The X-ray photoelectron spectroscopy analysis revealed that the Ni 2p spectrum of the sample with a 5:5 ratio exhibited different characteristics, and the hydroxide ratio was higher than that of the other samples. This finding indicated enhanced hydrophilicity of the sample. Owing to these characteristics, the (Ni:Co) 5:5 sample exhibited superior performance.