Anion-Directed Engineering of High-Entropy Layered Double Hydroxides for Oxygen Evolution Catalysis.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Efficient hydrogen production via anion exchange membrane water electrolysis (AEMWE) requires active and durable oxygen evolution reaction (OER) electrocatalysts.
• High-entropy materials offer tunable compositions and synergistic effects for advanced electrocatalysis.

Purpose of the Study:

• To investigate the influence of different anions (sulfate, nitrate, chloride) on the properties and OER performance of high-entropy layered double hydroxides (HELDHs).
• To understand how anion-induced microenvironmental changes affect nanomaterial morphology, surface structure, and catalytic activity.

Main Methods:

• Synthesis of high-entropy layered double hydroxides (HELDHs) using Fe, Co, Ni, Mn, and Zn with varying anions.
• Characterization of nanomaterial morphology, surface structure, and electrochemical properties.
• Evaluation of OER activity and stability in alkaline media and as anode catalysts in AEMWE.
• Density functional theory (DFT) calculations to elucidate the mechanism of enhanced activity.

Main Results:

• Anions significantly influenced HELDH morphology, yielding nanosheets, nanowires, and porous flower-like structures.
• Sulfate-based HELDHs (HELDH-SO₄^2-) displayed a porous nanosheet architecture with outstanding OER activity (282 mV at 100 mA cm^-2) and stability.
• HELDH-SO₄^2- demonstrated exceptional performance as anode catalysts in AEMWE.
• DFT calculations indicated that cation vacancies and adsorbed sulfate ions reduce the reaction energy barrier.

Conclusions:

• Anions play a pivotal role in tuning the structure-function relationship of high-entropy catalysts.
• Sulfate-based HELDHs represent a promising strategy for designing high-performance water oxidation electrocatalysts.
• The findings provide insights for developing efficient catalysts for hydrogen production via AEMWE.