Electrocatalytic Water Oxidation at Quinone-on-Carbon: A Model System Study.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Nanocarbon materials offer efficient electrocatalytic water oxidation via surface oxygen groups.
• Mechanistic understanding of metal-free carbon catalysts in oxygen evolution reaction (OER) remains controversial.
• Identifying specific active sites is crucial for designing advanced catalysts.

Purpose of the Study:

• To elucidate the molecular-level roles of different oxygen species in OER on nanocarbon surfaces.
• To identify the precise active sites responsible for efficient OER in metal-free carbon systems.
• To develop a facile protocol for creating well-defined oxygen-functionalized nanocarbon catalysts.

Main Methods:

• Synthesized aromatic molecule-modified nanocarbon systems using onion-like carbons (OLC) and multiwalled carbon nanotubes (MWCNT).
• Utilized eight types of aromatic molecules with designated single oxygen species as model structures.
• Investigated reaction mechanisms using H/D kinetic isotope effects to determine rate-determining steps.

Main Results:

• Edge quinones within a conjugated π network were identified as the true active sites for OER.
• Ether and carboxyl groups were found to be inactive in the OER process.
• Quinone-modified carbon systems demonstrated high catalytic activity, with turnover frequencies comparable to metal-based catalysts.

Conclusions:

• Edge quinones are the key active centers for OER on nanocarbon catalysts.
• Understanding specific active sites enables the rational design of highly efficient metal-free OER catalysts.
• This work provides a molecular-level mechanistic insight into OER on functionalized nanocarbons.