Microwave Hydrothermal Synthesis of Mesoporous First-Row Transition Metal Ferrites

Nanocrystalline and monomodal pore size mesoporous transition metal oxides have attracted considerable attention because of their interconnected networks and high surface areas. These materials have demonstrated improved characteristics such as electron transport, dye loading, electrolyte permeation, and oxidative capabilities when compared to those of typical nanostructured catalysts when used for different catalytic applications. Of particular interest are ferrites that have demonstrated roles in biomedical and magnetic devices, rechargeable batteries, sensors, catalysis, and water treatment. In addition, microwave hydrothermal synthesis is an attractive method due to its simplicity, rapid synthesis rate, and ease of operation. This paper details the synthesis of mesoporous first-row transition metal ferrites. M2+ (Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+) ferrite synthesis was systematically studied using a Biotage Initiator microwave apparatus, and the effects of reaction time and initial M2+ concentration on the crystal structure, morphology, composition, and magnetic and catalytic activities were evaluated. Various characterization techniques were utilized to study the synthesis mechanism and characteristics of the materials. These materials were then applied to the electrochemical oxygen evolution reaction, where NiFe2O4 showed high activity vs other ferrites with a low overpotential of 278 mV at 10 mA/cm2.