Robust Molecular Anodes for Electrocatalytic Water Oxidation Based on Electropolymerized Molecular Cu Complexes

Area of Science:

• Coordination Chemistry
• Materials Science
• Electrochemistry

Background:

• Development of efficient molecular catalysts for water oxidation is crucial for renewable energy technologies.
• Macrocyclic ligands offer tunable coordination environments for metal centers, influencing catalytic activity.
• Thiophene functionalization can enable surface immobilization and film formation for heterogeneous catalysis.

Purpose of the Study:

• To synthesize and characterize a novel tetra-amidate macrocyclic ligand with alkyl-thiophene moieties.
• To investigate the electrochemical properties and catalytic activity of its copper complexes, particularly for water oxidation.
• To develop stable molecular anodes based on polymerized copper complexes for efficient oxygen evolution.

Main Methods:

• Multistep synthesis of the tetra-amidate macrocyclic ligand (H4L).
• Complexation of the ligand with Cu(II) and subsequent oxidation to Cu(III) complexes.
• Characterization using spectroscopic techniques (XAS) and electrochemical methods.
• Electropolymerization of the copper complex onto various graphitic electrode surfaces (GC, CNTs).
• Electrocatalytic water oxidation studies under neutral pH conditions.

Main Results:

• Successful synthesis and characterization of the H4L ligand and its Cu(II)/Cu(III) complexes.
• Formation of stable thin films via electropolymerization of the [LCu]2- complex on electrode surfaces.
• Demonstrated electrocatalytic activity for water oxidation to dioxygen at neutral pH with high current densities (0.4 mA cm-2 at 1.30 V vs NHE).
• Achieved excellent stability and turnover numbers (TONs > 7600) over 24 hours without significant loss of catalytic activity.

Conclusions:

• The novel macrocyclic copper complex can be electropolymerized to form robust molecular anodes.
• These molecular anodes exhibit efficient and stable electrocatalytic activity for water oxidation under neutral pH conditions.
• The developed system represents a promising advancement in molecular electrocatalysis for sustainable energy applications.