A cobalt complex with a bioinspired molybdopterin-like ligand: a catalyst for hydrogen evolution

Area of Science:

• Inorganic Chemistry
• Catalysis
• Bioinorganic Chemistry

Background:

• Cobalt dithiolene complexes represent a new frontier in hydrogen-evolving catalysis.
• Bioinspired ligands can enhance catalyst performance by mimicking natural cofactors.
• The molybdopterin cofactor in formate dehydrogenases is a key model for such bioinspired designs.

Purpose of the Study:

• To synthesize and characterize a novel cobalt complex featuring a bioinspired quinoxaline-pyran-fused dithiolene ligand (qpdt(2-)).
• To evaluate the electrochemical catalytic activity of this complex for proton reduction and hydrogen evolution.
• To elucidate the mechanism of hydrogen formation using computational methods.

Main Methods:

• Synthesis and structural characterization of the cobalt dithiolene complex.
• Electrochemical studies to assess catalytic activity, including turnover frequency, faradaic yield, and stability.
• Density functional theory (DFT) calculations to investigate the reaction mechanism and energetic profiles.

Main Results:

• The synthesized cobalt complex with the qpdt(2-) ligand demonstrated significant activity for electrochemical proton reduction under weakly acidic conditions.
• The catalyst exhibited high turnover frequency, excellent faradaic yields, and remarkable stability.
• DFT calculations revealed that ligand protonation reduces overpotentials by 520 mV, with H2 formation proceeding via a Co-H intermediate and sulfur atom acting as a proton relay.

Conclusions:

• The novel cobalt dithiolene complex with a bioinspired ligand is a highly efficient electrocatalyst for hydrogen evolution.
• The bioinspired design effectively mimics natural enzyme active sites, leading to enhanced catalytic performance.
• Understanding the proton relay mechanism provides insights for designing future advanced catalysts.