It is a great challenge to fabricate a metal-free oxygen reduction reaction (ORR) electrocatalyst that can operate well in the acidic medium and fuel cells system. Here, a metal-free carbon material C-900 with abundant defect sites is fabricated by a self-sacrificed template and a solid-state reaction strategy. C-900 shows a superior performance to 20% Pt/C in alkaline medium and a performance closer to 20% Pt/C in acidic condition. It can thus be applied in air-breathing fuel cell (without extra operation pressure) as the cathode catalyst, which shows a high performance (1160 W L-1; ∼62% of 20% Pt/C) with excellent stability. By using oxygen temperature-programmed desorption, the strong selective chemisorption of O2 on C-900 has been revealed. The excellent chemisorption property of C-900 may originate from the large amounts of carbon defect sites, which have been confirmed by synchrotron radiation-based X-ray absorption spectroscopy. The rich defect sites and excellent chemisorption property can thus induce reversible carbon-oxygen interface for the excellent ORR activity.
Keywords: O2-chemisorption; air-breathing fuel cell; carbon defect; oxygen reduction; reversible carbon−oxygen interfaces.