Low-temperature synthesis and investigation into the formation mechanism of high quality Ni-Fe layered double hydroxides hexagonal platelets

Abstract

This paper describes the wet-chemistry synthesis of highly crystalline hexagonal fakes of Ni-Fe layered double hydroxide (LDH) produced at temperature as low as 100°C. The fakes with diameter in the range of 0.5–1.5μm and the thickness between 15 and 20nm were obtained by homogeneous precipitation method with the use of triethanolamine (TEA) and urea. By analyzing the intermediate products, it is suggested that, diferently from previous reports, a thermodynamically metastable iron oxyhydroxide and Ni-TEA complex are frstly formed at room temperature. Subsequently, when the mixture is heated to 100°C and the pH increases due to the thermal decomposition of urea, Ni2+ and Fe3+ are slowly released and then recombine, thus leading to formation of pure, highly-crystalline Ni-Fe LDH fakes. This material showed promising results as an electrocatalyst in oxygen evolution reaction (OER) providing an overpotential value of 0.36V.