Oxidizing Vacancies in Nitrogen-Doped Carbon Enhance Air-Cathode Activity.

Oxidizing vacancies in nitrogen-doped carbon have recently been reported to enhance the oxygen reaction activity of air cathodes, but their specific role has remained elusive and controversial. Herein, the critical role of oxidizing the vacancies in enhancing the oxygen reduction reaction for metal-air battery is identified with density functional theory. Deliberate introduction of oxygen-enriched vacancies in nitrogen-doped carbon is shown experimentally to provide superior oxygen reduction activity. In situ X-ray powder diffraction gives direct observation of the oxygen reactions in a zinc-air battery catalyzed by vacancy-enriched oxidized carbon; the intensity changes of the carbon peak show continuous chemisorption of oxygen intermediates on the carbon cathode during discharge. The air-cathode performance is shown to exceed that with Pt/C+IrO2 catalysts.