NdO-Intensified Dual-Site Synergy in IrMnO_x for Acidic Oxygen Evolution

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing low-iridium (Ir) electrocatalysts for proton exchange membrane water electrolyzers (PEMWEs) is crucial for efficient hydrogen production.
• Conventional iridium oxide (IrO₂) catalysts face challenges in activity and cost-effectiveness.

Purpose of the Study:

• To synthesize and evaluate a novel IrNdMnOₓ catalyst for enhanced performance in PEMWEs.
• To investigate the structural and electronic properties influencing the catalyst's activity and stability.

Main Methods:

• Synthesis of a triple solid-solution oxide (IrNdMnOₓ) by incorporating neodymium oxide (NdOₓ) into an IrMnOₓ matrix.
• Electrochemical characterization including mass-specific activity and overpotential measurements.
• Long-term stability testing in a PEMWE cell.
• Analysis using differential electrochemical mass spectroscopy (DEMS) and X-ray absorption spectroscopy (XAS).

Main Results:

• The IrNdMnOₓ catalyst exhibited a mass-specific activity of 769 A g⁻¹ at ultralow Ir loading (0.09 mg<0xE1><0xB5><0xA2>ᵣ cm⁻²), with an overpotential of 331 mV @ 100 mA cm⁻².
• Achieved stable operation at 1 A cm⁻² for over 800 hours at ~1.78 V in a PEMWE cell.
• Neodymium doping induced an asymmetric Nd-O-Ir-O-Mn structure, optimizing Ir-Mn distance and electronic properties.

Conclusions:

• NdOₓ doping is an effective strategy to enhance the activity, stability, and cost-efficiency of Ir-based catalysts for acidic oxygen evolution reaction (OER).
• The developed catalyst advances the development of sustainable hydrogen production technologies.
• The unique coordination structure promotes the oxygen-oxygen radical coupling mechanism (ORCM).