Zinc-Substituted Cobalt Phosphate [ZnCo₂(PO₄)₂] as a Bifunctional Electrocatalyst

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Developing efficient, earth-abundant, and stable bifunctional electrocatalysts is crucial for next-generation metal-air batteries.
• Cobalt-based phosphates offer a versatile platform for electrocatalyst design through cation substitution.
• Distorted phosphate geometries enhance water molecule binding and reduce overpotential.

Purpose of the Study:

• To investigate zinc-substituted cobalt phosphate, ZnCo2(PO4)2, as a bifunctional electrocatalyst.
• To elucidate the structural basis for its enhanced electrocatalytic activity.
• To assess its potential for application in metal-air batteries.

Main Methods:

• Crystal structure determination of ZnCo2(PO4)2.
• Evaluation of bifunctional electrocatalytic activity for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).
• Ex situ diffraction, electron microscopy, and ab initio calculations to probe activity origin and stability.

Main Results:

• ZnCo2(PO4)2 exhibits a monoclinic structure with distorted CoO5/ZnO5 trigonal bipyramids.
• Achieved onset potentials of 0.87 V (vs RHE) for ORR and 1.50 V (vs RHE) for OER.
• Demonstrated robust structural stability and performance comparable to precious metal catalysts.

Conclusions:

• Zinc-substituted cobalt phosphate, ZnCo2(PO4)2, is a promising bifunctional electrocatalyst for metal-air batteries.
• Tunable local cobalt coordination contributes to its enhanced catalytic properties.
• The material's stability and efficiency make it a viable alternative to precious metal catalysts.