Bioinspired Diiron Complex with Proton Shuttling and Redox-Active Ligand for Electrocatalytic Hydrogen Evolution

Area of Science:

• Inorganic Chemistry
• Electrochemistry
• Catalysis

Background:

• Development of efficient catalysts for hydrogen evolution is crucial for sustainable energy.
• Diiron complexes with redox-active ligands offer promising avenues for catalytic applications.

Purpose of the Study:

• To synthesize and characterize a novel μ-oxo diiron complex with a thiazoline-derived ligand.
• To investigate the electrocatalytic hydrogen evolution reaction (HER) activity of the complex.
• To elucidate the mechanism of HER, including the role of the ligand and acid.

Main Methods:

• Synthesis and characterization of the μ-oxo diiron complex.
• Electrochemical analysis (cyclic voltammetry) to study redox behavior and catalytic activity.
• Fourier transform infrared (FTIR) spectroscopy to identify the active species.
• Density functional theory (DFT) calculations to investigate reaction pathways and intermediates.

Main Results:

• The synthesized [Fe(μ-O)-Fe] complex demonstrated electrocatalytic HER activity in dimethylformamide with various organic acids.
• Electrochemical analysis revealed the complex is a precatalyst, generating an active species through a two-electron reduction.
• FTIR and DFT studies indicated the active catalyst features a bridged hydroxo unit and a proton-transferring thiazolinium moiety.
• The mechanism involves stepwise electron transfer and protonation, with proposed ECEC or EECC pathways depending on acid strength.

Conclusions:

• The μ-oxo diiron complex effectively catalyzes hydrogen evolution.
• The catalytic mechanism involves a unique interplay between the diiron core, a bridged hydroxo unit, and the redox-active thiazoline ligand.
• Understanding these pathways provides insights for designing advanced electrocatalysts for HER.