title: Long-range electron transfer over graphene-based catalyst for high-performing oxygen reduction reactions: importance of size, N-doping, and metallic impurities.
abstract: N-doped carbon materials are considered as next-generation oxygen reduction reaction (ORR) catalysts for fuel cells due to their prolonged stability and low cost. However, the underlying mechanism of these catalysts has been only insufficiently identified, preventing the rational design of high-performing catalysts. Here, we show that the first electron is transferred into O2 molecules at the outer Helmholtz plane (ET-OHP) over a long range. This is in sharp contrast to the conventional belief that O2 adsorption must precede the ET step and thus that the active site must possess as good an O2 binding character as that which occurs on metallic catalysts. Based on the ET-OHP mechanism, the location of the electrode potential dominantly characterizes the ORR activity. Accordingly, we demonstrate that the electrode potential can be elevated by reducing the graphene size and/or including metal impurities, thereby enhancing the ORR activity, which can be transferred into single-cell operations with superior stability.
authors.affiliation: Department of Chemical and Biomolecular Engineering and ‡Graduate School of EEWS, Korea Advanced Institute of Science and Technology , Daejeon 305-701, Republic of Korea.
authors.forename: Chang Hyuck
authors.initials: CH
authors.lastname: Choi
authors.forename: Hyung-Kyu
authors.initials: HK
authors.lastname: Lim
authors.forename: Min Wook
authors.initials: MW
authors.lastname: Chung
authors.forename: Jong Cheol
authors.initials: JC
authors.lastname: Park
authors.forename: Hyeyoung
authors.initials: H
authors.lastname: Shin
authors.forename: Hyungjun
authors.initials: H
authors.lastname: Kim
authors.forename: Seong Ihl
authors.initials: SI
authors.lastname: Woo