O2 reduction on graphite and nitrogen-doped graphite: experiment and theory

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Oxygen electroreduction is crucial for energy conversion technologies.
• Hydrogen peroxide (H2O2) is a valuable chemical intermediate.
• Carbon materials are widely explored as electrocatalysts.

Purpose of the Study:

• To investigate the electroreduction of oxygen to hydrogen peroxide using nitrided carbon.
• To elucidate the catalytic mechanism through experimental and theoretical studies.
• To understand the role of nitrogen doping and surface structure.

Main Methods:

• Experimental electrocatalytic measurements using nitrided Ketjenblack.
• Quantum chemical calculations on model graphite systems.
• Analysis of reaction intermediates and active sites.

Main Results:

• Nitrided Ketjenblack shows an enhanced onset potential (approx. 0.5 V SHE) for O2 reduction compared to untreated carbon (0.2 V SHE).
• Substitutional nitrogen creates active radical sites for O2 electroreduction to H2O2 via an OOH intermediate.
• Catalytic activity is dependent on the proximity of nitrogen atoms to graphite edges; distant N atoms are more active.

Conclusions:

• Nitrogen doping effectively enhances the electrocatalytic activity of carbon for H2O2 production.
• The mechanism involves specific carbon radical sites adjacent to substitutional nitrogen.
• Understanding the site-specific activity is key for designing efficient electrocatalysts.