Engineering d-d Coupling-Induced Ferromagnetic Catalysts for Boosting the Spin-Polarized Water Oxidation

Area of Science:

• Materials Science
• Catalysis
• Electrochemistry

Background:

• Spin catalysts offer unique spin-selective magneto-electric properties, crucial for advanced applications.
• Designing high-performance spin catalysts with ferromagnetic ordering and high conductivity is challenging for efficient spin-selective water electrolysis.

Purpose of the Study:

• To develop a novel anion-mediated d-d coupling strategy for high-performance ferromagnetic spin catalysts.
• To engineer cobalt oxide catalysts for enhanced oxygen evolution reaction (OER) performance and magnetic field responsiveness.

Main Methods:

• Anion-mediated d-d coupling strategy using Boron (B) substitution in cobalt oxide (Co3O4).
• Characterization of magnetic properties, electronic structure (density of states), and carrier concentration.
• Electrochemical analysis including overpotential measurements for oxygen evolution reaction (OER).
• In-situ Attenuated Total Reflection Surface-Enhanced Infrared Absorption Spectroscopy (ATR-SEIRAS) and theoretical calculations.

Main Results:

• B substitution induced high-spin Co2+ (Co2+Oh) and ferromagnetic coupling (TC > 850 K) from antiferromagnetic coupling (TN = 25 K).
• The Co3O3.65B0.35 catalyst exhibited enhanced carrier concentration and reduced electron transfer resistance.
• Achieved a significantly lower overpotential (295 mV at 30 mA cm-2) for OER compared to pristine Co3O4 (441 mV).
• An applied magnetic field (500 mT) further reduced the OER overpotential by 25.3%.

Conclusions:

• The d-d exchange interaction engineering strategy is effective for designing ferromagnetic OER catalysts.
• Enhanced orbital overlap and strengthened σ-bonding interactions upon spin alignment promote OOH intermediate adsorption.
• This work provides a pathway for developing magnetic field-responsive electrocatalysts for water electrolysis.