Mechanistic Insights into Electrocatalytic Hydrogen Evolution by an Exceptionally Stable Cobalt Complex

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Molecular catalysts are crucial for energy conversion reactions.
• Cobalt complexes are promising for proton reduction catalysis.
• Understanding reaction mechanisms is key to catalyst development.

Purpose of the Study:

• To electrochemically probe the catalytic mechanism of Co(aPPy) for proton reduction.
• To investigate the influence of solvent and pH on the catalytic pathway.
• To identify the active species and factors contributing to high catalytic activity.

Main Methods:

• Electrochemical analysis in organic solvents and water.
• Proton reduction activity measurements.
• Constant potential bulk electrolysis.

Main Results:

• Catalytic mechanisms vary with solvent and acid strength.
• In aqueous media, Co(aPPy) acts as a precatalyst to a more active species.
• Dissociated pyridine acts as a proton relay at pH ≤ 5, enhancing activity.
• Optimal catalyst stability and activity observed at pH 3 in aqueous solution.

Conclusions:

• Co(aPPy) exhibits complex, pH- and solvent-dependent electrocatalytic mechanisms for proton reduction.
• In acidic aqueous solutions, a dissociated pyridine ligand facilitates proton transfer, leading to high activity and stability.
• This work provides insights for designing advanced molecular catalysts for hydrogen production.