Monolayer NiIr-Layered Double Hydroxide as a Long-Lived Efficient Oxygen Evolution Catalyst for Seawater Splitting

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Seawater splitting for hydrogen production requires efficient oxygen evolution reaction (OER) catalysts.
• Existing OER catalysts struggle with corrosion and chloride oxidation in saline environments.
• 5d transition metals offer potential for enhanced catalytic properties.

Purpose of the Study:

• To develop a highly active and stable OER catalyst for seawater splitting.
• To investigate the role of iridium (Ir) incorporation in layered double hydroxides (LDHs).
• To understand the mechanism behind the enhanced catalytic performance.

Main Methods:

• Synthesis of monolayer NiIr-layered double hydroxide (NiIr-LDH).
• Electrochemical measurements including overpotential and Faradaic efficiency.
• Long-term chronopotentiometry for stability testing.
• X-ray absorption fine structure (XAFS) and density functional theory (DFT) calculations.
• In situ Raman spectroscopy.

Main Results:

• NiIr-LDH achieved 500 mA/cm² at 361 mV overpotential with 99% O₂ Faradaic efficiency in alkaline seawater.
• Outperformed commercial IrO₂ (763 mV, 23%) and NiFe-LDH (530 mV, 92%) in activity and efficiency.
• Demonstrated exceptional stability with negligible activity loss over 650 hours at 500 mA/cm².
• DFT and XAFS revealed altered electron densities at Ni and Ir sites, accelerating intermediate formation.
• Electrochemical and spectroscopic data coupled with DFT confirmed accelerated generation of *O and *OOH intermediates.

Conclusions:

• Monolayer NiIr-LDH is a highly effective catalyst for seawater splitting OER.
• Iridium incorporation significantly enhances catalytic activity and stability.
• The enhanced performance is attributed to accelerated intermediate formation on Ni and Ir sites.
• This work opens avenues for using 5d metals in LDH materials for diverse applications beyond seawater splitting.