Ligand Isomerization Driven Electrocatalytic Switching.

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• The central metal ion is traditionally considered the primary determinant of molecular catalyst selectivity.
• Ligands are typically viewed as modulators of reaction kinetics rather than selectivity.

Purpose of the Study:

• To challenge the prevailing paradigm regarding the role of ligands in molecular catalysis.
• To demonstrate the significant influence of ligand isomerization on reaction selectivity.
• To develop a novel cobalt-based molecular catalyst for the direct 4-electron oxygen reduction reaction (ORR).

Main Methods:

• Investigated the effect of ligand isomerization on a cobalt phthalocyanine catalyst.
• Analyzed the mechanism of the oxygen reduction reaction (ORR) using detailed mechanistic studies.
• Tested the catalyst's performance in an actual H2-O2 fuel cell.

Main Results:

• Ligand isomerization drastically altered the ORR selectivity from a 2-electron to a 4-electron pathway.
• Intramolecular hydrogen bonds within the ligand were identified as key to activating the cobalt center and directing oxygen binding.
• The novel cobalt catalyst achieved activity comparable to platinum for the direct 4-electron ORR.
• The observed effect of ligand isomerism was generalizable across different central metal ions.

Conclusions:

• Ligands play a crucial role in determining the selectivity of molecular catalysts, contrary to established views.
• Ligand isomerization offers a powerful strategy for designing highly selective molecular catalysts.
• This research opens new possibilities for developing advanced catalysts for energy conversion applications, such as fuel cells.