Spinel-Structured High Entropy Oxides: Low Temperature Synthesis, Characterization, and Potential Applications.

Area of Science:

• Materials Science
• Inorganic Chemistry
• Electrochemistry

Background:

• High entropy oxides (HEOs) are gaining attention for their unique properties and cost-effectiveness.
• Developing scalable, low-temperature synthesis methods for HEOs is crucial for their practical application.

Purpose of the Study:

• To report a simple, scalable, and low-temperature method for synthesizing spinel (FeNiCoCuZn)3O4 HEO.
• To characterize the synthesized HEO's magnetic, electrochemical, and electrocatalytic properties.

Main Methods:

• Synthesis of spinel (FeNiCoCuZn)3O4 HEO by heating an aqueous solution of divalent cations in a high alkali environment (1 M KOH) at 95 °C for 24 h under atmospheric pressure.
• Characterization of magnetic properties (mass susceptibility).
• Evaluation of electrochemical lithium storage performance and electrocatalytic oxygen evolution reaction (OER) activity.

Main Results:

• The synthesized HEO exhibited paramagnetic behavior at room temperature (χ = (7.5 ± 0.2) × 10^-7 m^3·kg^-1).
• Demonstrated stable electrochemical lithium storage with a gravimetric capacity of ~300 mAh·g^-1 at 100 mA·g^-1.
• Showed activity in the electrocatalytic oxygen evolution reaction with an overpotential of 460 mV in alkaline media.
• Band gap energy was determined to be approximately 2.4 eV.

Conclusions:

• A facile, scalable, and low-temperature hydrothermal method was established for synthesizing spinel (FeNiCoCuZn)3O4 HEO.
• The synthesized HEO possesses promising properties for energy storage (lithium-ion batteries) and energy production (OER catalysis).
• This advancement offers a viable pathway for next-generation transition metal-based HEO materials.