Excellent Bifunctional Oxygen Evolution and Reduction Electrocatalysts (5A_1/5)Co₂O₄ and Their Tunability

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable metal-air batteries and hydrogen fuel cells require efficient, cost-effective electrocatalysts for oxygen evolution (OER) and oxygen reduction (ORR).
• Economically feasible and earth-abundant materials are crucial for sustainable energy technologies.

Purpose of the Study:

• To investigate nano (5A_1/5)Co₂O₄ compositionally complex oxides (CCOs) as bifunctional electrocatalysts for OER and ORR.
• To identify optimal synthesis and processing conditions for enhanced catalytic performance in alkaline media.

Main Methods:

• Synthesis of nano (5A_1/5)Co₂O₄ CCOs using a low-temperature soft-templating method.
• Postannealing heat treatment at 600 °C to optimize the material structure and performance.
• Electrochemical characterization including overpotential, Tafel slope, onset potential, H₂O₂ yield, and chronoamperometry.

Main Results:

• The (Mn_0.2Fe_0.2Ni_0.2Cu_0.2Zn_0.2)Co₂O₄ composition exhibited exceptional OER overpotential (260 mV at 10 mA cm^-2) and a favorable Tafel slope (68 mV dec^-1).
• This catalyst demonstrated excellent ORR onset potential (0.9 V) with low H₂O₂ yields (<6%) over a wide potential range.
• The material showed remarkable stability over 22 hours of chronoamperometry, confirmed by X-ray photoelectron spectroscopy.

Conclusions:

• CCO ACo₂O₄ spinel oxides are highly promising bifunctional electrocatalysts for sustainable energy applications.
• The tunability of CCOs through chemical substitutions and processing offers a pathway for designing advanced electrocatalysts.
• The cost-effective and scalable synthesis method further enhances their potential for commercial viability.