Low-temperature synthesis of high quality Ni-Fe layered double hydroxides hexagonal platelets

TL;DR

This study presents a low-temperature wet-chemistry method to synthesize highly crystalline Ni-Fe layered double hydroxide hexagonal platelets, demonstrating their potential as efficient electrocatalysts for oxygen evolution reactions.

Contribution

It introduces a novel low-temperature synthesis process for Ni-Fe LDH flakes and elucidates the formation mechanism involving metastable intermediates.

Findings

Successful synthesis at 100°C with high crystallinity

Flakes with 0.5-1.5 μm diameter and 15-20 nm thickness

Electrocatalytic performance with 0.36 V overpotential for OER

Abstract

This paper describes the wet-chemistry synthesis of highly crystalline hexagonal flakes of Ni-Fe layered double hydroxide (LDH) produced at temperature as low as 100 oC. The flakes with diameter in the range of 0.5-1.5 um and the thickness between 15 and 20 nm were obtained by homogeneous precipitation method with the use of triethanolamine (TEA) and urea. By analyzing the intermediate products, it is suggested that, differently from previous reports, a thermodynamically metastable iron oxyhydroxide and Ni-TEA complex are firstly formed at room temperature. Subsequently, when the mixture is heated to 100 oC 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 flakes. This material showed promising results as an electrocatalyst in oxygen evolution reaction (OER) providing an overpotential value of 0.36 V.