Anion controlled selectivity in oxygen reduction catalysed by a dinuclear cobalt N,O-Schiff base complex.

Area of Science:

• Inorganic Chemistry
• Catalysis
• Electrochemistry

Background:

• Oxygen reduction reaction (ORR) is crucial for energy conversion.
• Developing efficient and selective ORR catalysts is a key challenge.
• Cobalt-based catalysts offer promise but often lack selectivity.

Purpose of the Study:

• To develop a new dinuclear cobalt complex for selective oxygen reduction.
• To investigate the influence of proton source on the ORR pathway.
• To elucidate the mechanism of oxygen reduction catalyzed by the cobalt complex.

Main Methods:

• Synthesis and characterization of a novel dinuclear cobalt complex.
• Electrochemical studies including cyclic voltammetry and rotating disk electrode measurements.
• Spectroscopic and computational studies to probe reaction intermediates and mechanisms.

Main Results:

• The cobalt complex selectively catalyzes the 4-electron reduction of O2 to water with high turnover frequency (TOF) and low overpotential.
• Replacing acetic acid with ammonium hexafluorophosphate as the proton source switches the reaction to the 2-electron pathway, producing H2O2.
• Mechanistic studies indicate a peroxo intermediate, with acetate coordination/decoordination controlling the electron transfer pathway.

Conclusions:

• A new dinuclear cobalt complex demonstrates efficient and selective ORR catalysis.
• Proton source plays a critical role in directing the ORR pathway selectivity.
• The findings provide insights into the design of advanced ORR catalysts for selective oxygen reduction to either water or hydrogen peroxide.