Direct Cl─Cl Coupling Over Atomically Dispersed Ir₂ Pairs for Efficient Chlorine Electrosynthesis

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The chlor-alkali industry relies on the chlorine evolution reaction (CER).
• Conventional dimensionally stable anodes (DSAs) exhibit limitations in noble-metal utilization and intrinsic activity.
• Developing highly efficient and stable electrocatalysts is crucial for advancing CER.

Purpose of the Study:

• To engineer a molecularly precise dual-atom catalyst (DAC) for efficient chlorine electrosynthesis.
• To investigate the catalytic mechanism and performance of atomically dispersed iridium diatomic pairs anchored on MnO2 nanorods (Ir2─MnO2).
• To demonstrate the catalyst's stability and selectivity in industrial applications, including seawater electrolysis.

Main Methods:

• Synthesis of atomically dispersed iridium diatomic pairs (Ir2) on MnO2 nanorods.
• Characterization using spherical aberration-corrected microscopy and X-ray absorption spectroscopy (XAS) to confirm diatomic structure.
• Electrochemical evaluation of CER performance, including overpotential and Tafel slope measurements.
• Kinetic analysis, operando Raman spectroscopy, and theoretical calculations to elucidate the reaction mechanism.

Main Results:

• Successfully synthesized Ir2─MnO2 featuring validated Ir2 diatomic pairs with a 3.16 Å interatomic distance.
• Achieved competitive CER performance with an overpotential of 36.9 mV at 10 mA cm-2 and a low Tafel slope of 34.6 mV dec-1.
• Demonstrated a direct *Cl─*Cl coupling mechanism facilitated by synergistic stabilization of intermediates on adjacent Ir-Ir dual atoms.
• Exhibited excellent durability, maintaining performance over 500 hours at high current densities in natural seawater electrolysis.

Conclusions:

• Atomically dispersed iridium diatomic pairs on MnO2 nanorods represent a highly effective DAC for chlorine electrosynthesis.
• Diatomic site engineering offers a powerful strategy to overcome limitations of traditional catalysts.
• The developed Ir2─MnO2 catalyst shows significant promise for industrial applications due to its efficiency, selectivity, and durability.