A bio-inspired coordination polymer as outstanding water oxidation catalyst via second coordination sphere...

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• First-row transition metal catalysts for oxygen evolution reaction (OER) often require high overpotentials.
• Developing efficient and stable OER catalysts is crucial for energy conversion technologies.

Purpose of the Study:

• To develop a highly active and stable electrocatalyst for OER using earth-abundant metals.
• To elucidate the mechanism of OER catalyzed by the novel material.

Main Methods:

• Synthesis of iron/nickel terephthalate coordination polymer on nickel foam (NiFeCP/NF).
• Electrochemical characterization including overpotential, Tafel slope, and stability tests in 1.0 M KOH.
• Mechanistic studies using deuterium kinetic isotope effects, proton inventory, and atom-proton-transfer measurements.

Main Results:

• NiFeCP/NF demonstrated outstanding OER activity with a low overpotential of 188 mV at 10 mA cm⁻².
• The catalyst exhibited excellent stability and a small Tafel slope.
• pH-independent OER activity suggested a concerted proton-coupled electron transfer (c-PET) as the rate-determining step (RDS).

Conclusions:

• Uncoordinated carboxylates in NiFeCP/NF function as proton transfer relays, accelerating the OER rate.
• This mechanism is analogous to proton relays in Photosystem II, offering insights for designing advanced water oxidation catalysts.