Soluble Gd₆Cu₂₄ clusters: effective molecular electrocatalysts for water oxidation

Area of Science:

• Inorganic Chemistry
• Catalysis
• Sustainable Energy

Background:

• The water oxidation half-reaction is a critical bottleneck in electrochemical and photocatalytic water splitting for hydrogen fuel generation.
• Developing efficient and robust catalysts is essential to overcome this limitation and enable scalable hydrogen production.

Purpose of the Study:

• To synthesize and characterize novel heterometallic clusters, specifically Gd6Cu24-IM and Gd6Cu24-AC.
• To evaluate the catalytic activity of these clusters for the water oxidation reaction.
• To elucidate the mechanism of O-O bond formation in the catalytic cycle.

Main Methods:

• Synthesis of Gd6Cu24-IM and Gd6Cu24-AC heterometallic clusters.
• Electrochemical and spectroscopic characterization of the catalysts.
• Kinetic studies to determine turnover frequencies and reaction mechanisms.

Main Results:

• The Gd6Cu24-IM cluster demonstrated a high turnover frequency of 319 s^-1 at pH 6.
• The catalytic mechanism involves a trimetallic site (H2O-GdIII CuII2-H2O) undergoing sequential electron and proton transfers.
• High-valent GdIII-O-O-CuIII2 intermediates were observed, with O-O bond formation facilitated by intramolecular interactions.

Conclusions:

• Heterometallic clusters can serve as efficient water oxidation catalysts.
• Synergistic effects between polymetallic sites are key to regulating O-O bond formation.
• This work offers a promising strategy for advancing water splitting technologies for hydrogen production.