title: M3C (M: Fe, Co, Ni) Nanocrystals Encased in Graphene Nanoribbons: An Active and Stable Bifunctional Electrocatalyst for Oxygen Reduction and Hydrogen Evolution Reactions.
abstract: Transition metal carbide nanocrystalline M3C (M: Fe, Co, Ni) encapsulated in graphitic shells supported with vertically aligned graphene nanoribbons (VA-GNRs) are synthesized through a hot filament chemical vapor deposition (HF-CVD) method. The process is based on the direct reaction between iron group metals (Fe, Co, Ni) and carbon source, which are facilely get high purity carbide nanocrystals (NCs) and avoid any other impurity at relatively low temperature. The M3C-GNRs exhibit superior enhanced electrocatalystic activity for oxygen reduction reaction (ORR), including low Tafel slope (39, 41, and 45 mV dec(-1) for Fe3C-GNRs, Co3C-GNRs, and Ni3C-GNRs, respectively), positive onset potential (∼0.8 V), high electron transfer number (∼4), and long-term stability (no obvious drop after 20 000 s test). The M3C-GNRs catalyst also exhibits remarkable hydrogen evolution reaction (HER) activity with a large cathodic current density of 166.6, 79.6, and 116.4 mA cm(-2) at an overpotential of 200 mV, low onset overpotential of 32, 41, and 35 mV, small Tafel slope of 46, 57, and 54 mV dec(-1) for Fe3C-GNRs, Co3C-GNRs, and Ni3C-GNRs, respectively, as well as an excellent stability in acidic media.
authors.affiliation: †College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing 100124, China.
authors.forename: Xiujun
authors.initials: X
authors.lastname: Fan
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Peng
authors.forename: Ruquan
authors.initials: R
authors.lastname: Ye
authors.forename: Haiqing
authors.initials: H
authors.lastname: Zhou
authors.affiliation: †College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing 100124, China.
authors.forename: Xia
authors.initials: X
authors.lastname: Guo
keywords: M3C (M: Fe, Co, Ni); hydrogen evolution reaction (HER); nanocrystals (NCs); oxygen reduction reaction (ORR); vertically aligned graphene nanoribbons (VA-GNRs)