Microwave Hydrothermal Synthesis of Mesoporous First-Row Transition Metal Ferrites

Abstract

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. M 2+ (Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ) ferrite synthesis was systematically studied using a Biotage Initiator microwave apparatus, and the effects of reaction time and initial M 2+ 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 NiFe 2 O 4 showed high activity vs other ferrites with a low overpotential of 278 mV at 10 mA/cm 2 .

Synthesis, Characterization, and Evaluation of Artemisia afra-Mediated Iron Nanoparticles as a Potential Nano-Priming Agent for Seed Germination

“…The two A 1g phonon mode were observed at 225 and 494 cm –1 , while three E g phonon modes correlate to the peaks at 298, 412, and 609.4 cm –1 . The other two peaks of E g are missing; this could be associated with the lower intensity as described by Achola et al These findings confirm that there could be a mixture of magnetite and hematite. Similar results of Fe 2 O 3 nanoparticles have also been shown by Marshall et al…”

“…The Raman spectrum at 298, 412, and 609.4 cm −1 . The other two peaks of E g are missing; this could be associated with the lower intensity as described by Achola et al 64 These findings confirm that there could be a mixture of magnetite and hematite. Similar results of Fe 2 O 3 nanoparticles have also been shown by Marshall et al 65 TGA was conducted to understand the thermal stability, decomposition temperature, and decomposition rate of the prepared nanoparticles.…”

A review on transition metal oxides in catalysis

“…The optimized nanosheets thus formed have proven to be effective OER catalyst with a greater stability (62 h) and an overpotential of 268 mV at 10 mA cm −2 . On a similar note, NiFe 2 O 4 synthesized using microwave assisted hydrothermal synthesis by Suib (Achola et al, 2022) has shown low overpotential of 278 mV at 10 mA cm −2 as an OER catalyst.…”

“…The seminal work on mesoporous materials by Mobil Corporation (Kresge et al, 1992) pioneered extensive research in the synthesis and utilization of porous TMOs. Nano-size mixed valent mesoporous oxides have received much attention in catalysis, electrochemistry, and adsorption due to their high surface areas and improved mass transfer within pores (Wang et al, 2017;Achola et al, 2022). Our lab has done considerable research on synthesizing mesoporous TMOs in recent years (Dang et al, 2021;Achola et al, 2022;Zhao et al, 2022a;Tabassum et al, 2022).…”

Highly Mesoporous MoO3 Catalysts for Electrophilic Aromatic Substitution

“…Among porous materials, mesoporous materials have fascinated researchers due to their enormous applications in catalysis, adsorption, electrochemistry, gas sensing, energy conversion and storage, and photochemistry. − To synthesize mesoporous materials, usually two types of templates (hard and soft) are utilized via different synthesis processes/methods. Some of the common synthesis process/methods are sol–gel, single-micelle-directed, inverse micelle, nanocasting, alignment and grafting, electrochemical, and the metal dissolution .…”