B, N Codoped and Defect-Rich Nanocarbon Material as a Metal-Free Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions.

ABSTRACT: The development of highly active, inexpensive, and stable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts to replace noble metal Pt and RuO₂ catalysts remains a considerable challenge for highly demanded reversible fuel cells and metal-air batteries. Here, a simple approach for the facile construction of a defective nanocarbon material is reported with B and N dopants (B,N-carbon) as a superior bifunctional metal-free catalyst for both ORR and OER. The catalyst is prepared by pyrolyzing the composites of ethyl cellulose and high-boiling point 4-(1-naphthyl)benzeneboronic acid in NH₃ atmosphere with an inexpensive Zn-based template. The obtained porous B,N-carbon with rich carbon defects exhibits excellent ORR and OER performances, including high activity and stability. In alkaline medium, B,N-carbon material shows high ORR activity with an onset potential (E_onset) reaching 0.98 V versus reversible hydrogen electrode (RHE), very close to that of Pt/C, a high electron transfer number and excellent stability. This catalyst also presents the admirable ORR activity in acidic medium with a high E_onset of 0.81 V versus RHE and a four-electron process. The OER activity of B,N-carbon is superior to that of the precious metal RuO₂ and Pt/C catalysts. A Zn-air battery using B,N-carbon as the air cathode exhibits a low voltage gap between charge and discharge and long-term stability. The excellent electrocatalytic performance of this porous nanocarbon material is attributed to the combined positive effects of the abundant carbon defects and the heteroatom codopants.

SUBMITTER: Sun T 

PROVIDER: S-EPMC6051395 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature