Covalent Functionalization of NiFe Layered Double Hydroxides using Tris(Hydroxymethyl)Aminomethane

In this work, we present the covalent functionalization of NiFe layered double hydroxides (LDHs) using tris(hydroxymethyl)aminomethane (TRIS) to enhance their stability, processability, and performance as catalysts for the oxygen evolution reaction (OER). LDHs are versatile materials with applications in energy storage, catalysis, and magnetism due to their tunable properties. TRIS molecules were covalently attached to NiFe-LDH using a modified hydrothermal method, confirmed through x-ray diffraction, infrared and Raman spectroscopy, x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, elemental analysis, thermogravimetric analysis, and DFT+U calculations. The TRIS-functionalized NiFe-LDH showed predominant antiferromagnetic behavior with a blocking temperature of 7.5 K and a coercive field of 3900 Oe at 2 K. This is attributed to enhanced structural order resulting from high synthesis temperatures enabled by TRIS, which prevent oxide formation at 180°C. Additionally, TRIS functionalization facilitates the creation of highly stable binder-free electrodes for OER in alkaline media via water-based ink formulation. The improved ink stability ensures better dispersion and deposition of the catalytic material, increasing surface area and electrocatalytic performance. While TRIS is removed during operation, its role in optimizing ink formulation and electrode integration makes NiFe-TRIS a robust and efficient catalyst for water splitting and electrochemical applications.