A molecular material based on electropolymerized cobalt macrocycles for electrocatalytic hydrogen evolution

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Developing efficient electrocatalysts for hydrogen evolution reaction (HER) is crucial for sustainable energy technologies.
• Cobalt-based complexes offer potential as active HER catalysts, but stability can be a challenge.

Purpose of the Study:

• To synthesize and characterize a novel electrocatalytic material for HER using electropolymerization.
• To evaluate the catalytic activity, efficiency, and stability of the synthesized material.

Main Methods:

• Electropolymerization of Co(ii) dibenzotetraaza[14]annulene (CoTAA) to form poly-CoTAA films.
• X-ray photoelectron spectroscopy (XPS) for material characterization.
• Electrochemical measurements to assess HER performance (overpotential, current density, Faradaic efficiency).

Main Results:

• Poly-CoTAA films preserved the [Co(II)-N4] motif, confirmed by XPS.
• An overpotential of -0.57 V was required for a current density of 1 mA cm⁻² at pH 4.6.
• A Faradaic efficiency of 90% for HER was observed over one hour, but demetallation occurred with prolonged electrolysis.

Conclusions:

• Electropolymerized poly-CoTAA is a promising electrocatalyst for HER in acidic media.
• The material exhibits good initial catalytic activity and efficiency.
• Partial demetallation under prolonged negative potentials limits long-term stability, indicating a need for further material optimization.