Facile Synthesis of Manganese‐Oxide‐Containing Mesoporous Nitrogen‐Doped Carbon for Efficient Oxygen Reduction

Abstract

Developing low‐cost non‐precious metal catalysts for high‐performance oxygen reduction reaction (ORR) is highly desirable. Here a facile, in situ template synthesis of a MnO‐containing mesoporous nitrogen‐doped carbon (m‐N‐C) nanocomposite and its high electrocatalytic activity for a four‐electron ORR in alkaline solution are reported. The synthesis of the MnO‐m‐N‐C nanocomposite involves one‐pot hydrothermal synthesis of Mn3O4@polyaniline core/shell nanoparticles from a mixture containing aniline, Mn(NO3)2, and KMnO4, followed by heat treatment to produce N‐doped ultrathin graphitic carbon coated MnO hybrids and partial acid leaching of MnO. The as‐prepared MnO‐m‐N‐C composite catalyst exhibits high electrocatalytic activity and dominant four‐electron oxygen reduction pathway in 0.1 M KOH aqueous solution due to the synergetic effect between MnO and m‐N‐C. The pristine MnO shows little electrocatalytic activity and m‐N‐C alone exhibits a dominant two‐electron process for ORR. The MnO‐m‐N‐C composite catalyst also exhibits superior stability and methanol tolerance to a commercial Pt/C catalyst, making the composite a promising cathode catalyst for alkaline methanol fuel cell applications. The synergetic effect between MnO and N‐doped carbon described provides a new route to design advanced catalysts for energy conversion.

Boron/Nitrogen-Codoped Carbon Nano-Onion Electrocatalysts for the Oxygen Reduction Reaction

“…Similar curves were obtained for p-CNOs and reference Pt/C catalysts (data not shown). As expected, an increase of the cathodic current can be observed for potential lower than the onset (about +0.78 V), followed by a quasi-plateau region, when diffusion limiting occurs . In addition, the diffusion-limiting current density J increases (in absolute value) with increasing rotation speed ω because the diffusion distance reduces for larger speed values .…”

Boosting oxygen reduction activity of spinel CoFe 2 O 4 by strong interaction with hierarchical nitrogen-doped carbon nanocages

“…S6 online) With increasing rotating rates, higher ORR current densities are observed for CoFe 2 O 4 /hNCNC as expected due to the shorter diffusion distance at higher rotating rate (Fig. 3c) [52]. The corresponding Koutecky-Levich (K-L) plots at 0.6, 0.4 and 0.2 V show a very good linearity, and the electron-transfer number (n) is calculated to be 3.60-3.80, indicating a first-order dependence of O 2 concentration and a predominant 4e process (Fig.…”

Cobalt nanoparticles embedded in N-doped carbon as an efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions

“…Meanwhile, short-range ordered, graphitized carbon was also observed from the HRTEM image (Fig.2d), and the inset of Fig.2dshows a Co nanoparticle surrounded by graphitized carbon. It should be noted that the metallic transition metal or oxide phases within graphitized carbon shells are supposed to be conducive to greatly enhance the catalytic activity of the catalysts, which has been reported in many previous research reports 10,38,43,44. Here it is also predictable that a similar mechanism may also work in our Co/N-C hybrid system due to the interaction between the small sized Co NPs and the N-doped graphitized carbon.X-ray photoelectron spectroscopy (XPS) was used to investigate the elemental composition of Co/N-C-800.…”

“…It should be noted that the metallic transition metal or oxide phases within graphitized carbon shells are supposed to be conducive to greatly enhance the catalytic activity of the catalysts, which has been reported in many previous research reports. 10,38,43,44 Here it is also predictable that a similar mechanism may also work in our Co/N-C hybrid system due to the interaction between the small sized Co NPs and the N-doped graphitized carbon.…”