Hydration-Effect-Promoting Ni-Fe Oxyhydroxide Catalysts for Neutral Water Oxidation

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Efficient oxygen evolution reaction (OER) catalysts are crucial for biohybrid fuel and chemical production, especially in pH-neutral electrolytes.
• Neutral electrolytes require OER catalysts to facilitate both water adsorption and dissociation due to low reactant concentrations.

Purpose of the Study:

• To investigate the role of hydrated metal cations in enhancing Ni-Fe framework catalysts for OER in neutral electrolytes.
• To develop novel OER catalysts that improve water adsorption and dissociation for efficient energy conversion.

Main Methods:

• Density functional theory (DFT) simulations to understand cation effects on water adsorption and dissociation.
• Room-temperature sol-gel process to incorporate hydration-effect-promoting (HEP) cations (e.g., Mg2+) into Ni-Fe frameworks.
• Electrochemical testing to evaluate catalyst performance (overpotential, stability) and compare with iridium oxide (IrO2).

Main Results:

• Ni-Fe-Mg catalysts demonstrated a low overpotential of 310 mV at 10 mA cm-2 in pH-neutral electrolytes, outperforming IrO2 by 40 mV.
• Catalysts exhibited excellent stability, operating continuously for over 900 hours.
• DFT and experimental results confirmed that HEP catalysts promote molecular water adsorption and dissociation.

Conclusions:

• Incorporating HEP metal cations, like Mg2+, into Ni-Fe frameworks is an effective strategy to enhance OER activity in neutral electrolytes.
• The developed Ni-Fe-Mg catalysts offer a promising solution for efficient biohybrid fuel and chemical production.