Binary and Ternary Doping of Nitrogen, Boron, and Phosphorus into Carbon for Enhancing Electrochemical Oxygen Reduction Activity

• Published in: ACS nano 2012-08, Vol.6 (8), p.7084-7091
• Main Authors: Choi, Chang Hyuck, Park, Sung Hyeon, Woo, Seong Ihl
• Format: Article
• Language: English
• Subjects: Alternations; Atomic properties; Boron - chemistry; Carbon; Carbon - chemistry; Catalysts; Charge; Doping; Electrochemistry - methods; Materials Testing; Media; Nanostructure; Nitrogen - chemistry; Oxidation-Reduction; Oxygen - chemistry; Phosphorus - chemistry; Reduction
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn3021234

N-doped carbon, a promising alternative to Pt catalyst for oxygen reduction reactions (ORRs) in acidic media, is modified in order to increase its catalytic activity through the additional doping of B and P at the carbon growth step. This additional doping alters the electrical, physical, and morphological properties of the carbon. The B-doping reinforces the sp2-structure of graphite and increases the portion of pyridinic-N sites in the carbon lattice, whereas P-doping enhances the charge delocalization of the carbon atoms and produces carbon structures with many edge sites. These electrical and physical alternations of the N-doped carbon are more favorable for the reduction of the oxygen on the carbon surface. Compared with N-doped carbon, B,N-doped or P,N-doped carbon shows 1.2 or 2.1 times higher ORR activity at 0.6 V (vs RHE) in acidic media. The most active catalyst in the reaction is the ternary-doped carbon (B,P,N-doped carbon), which records −6.0 mA/mg of mass activity at 0.6 V (vs RHE), and it is 2.3 times higher than that of the N-doped carbon. These results imply that the binary or ternary doping of B and P with N into carbon induces remarkable performance enhancements, and the charge delocalization of the carbon atoms or number of edge sites of the carbon is a significant factor in deciding the oxygen reduction activity in carbon-based catalysts.