One-dimension (1D) heteroatom-doped mesoporous carbon is a promising alternative catalyst for oxygen reduction reaction (ORR). This work reported a hybrid ORR electrocatalyst composed of Co/CoOx nanoparticles embedded in N-doped mesoporous carbon layer coated on carbon nanotubes (CNTs@Co–N–C). Owing to the 1D mesoporous architecture with abundant active sites, CNTs@Co–N–C hybrid showed superior ORR activity, high selectivity, and long-term durability. Moreover, as cathode catalyst for primary Zn–air battery, CNTs@Co–N–C also showed excellent performance comparable to Pt/C. Thus, this study can offer a good idea for preparing noble-metal-free electrocatalysts for energy applications.

A salt crystal-templating synthesis route is proposed to synthesize a Fe-N-C catalyst with well-controlled mesoporous structure. In the presence of glucose, NaCl-template can efficiently tune the porous structure of catalyst and help to improve the oxygen reduction reaction (ORR) activity. The optimized catalyst possesses a hierarchical mesopore size distribution, a high Brunauer-Emmett-Teller surface area (up to 911.56 m(2) g(-1)) and homogeneous distribution of abundant active sites. As a result, the obtained catalyst shows a desirable ORR activity in alkaline medium (half-wave potential of 0.84 V and kinetic mass activity at 0.8 V of 24.95 A g(-1)), high selectivity (electron transfer number >3.92), excellent long term durability (only 16 mV negative shift of half-wave potential after 5000 potential cycles in O-2-saturated 0.1 M KOH) and good tolerance to methanol. The enhanced electrochemical performance enables the proposed catalyst to be the promising electrocatalyst candidate to commercial Pt/C towards ORR. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The development of efficient nonprecious metal catalysts for oxygen reduction reaction (ORR) is crucial but challenging. Herein, one simple and effective strategy is developed to synthesize bimetallic nitrogen-doped carbon catalysts by pyrolyzing Fe-doped Vitamin B12 (VB12) supported carbon black (Fe-VB12/C). A typical Fe-20-VB12/C catalyst with a nominal iron content of 20 wt% pyrolyzed at 700 degrees C exhibits remarkably ORR activity in alkaline medium (half-wave potential of 0.88 V, 10 mV positive than that of commercial Pt/C), high selectivity (electron transfer number > 3.93), excellent stability (only 6 mV negative shift of half-wave potential after 5000 potential cycles) and good methanol-tolerance. The superior ORR activity of the composite is mainly attributed to the improved mesoporous structure and co-existence of abundant Fe-N-x and Co-N-x active sites. Meanwhile, the metallic Fe are necessary for the improved ORR activity by means of the interaction of metallic Fe with neighboring active sites. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

To improve the catalytic activity towards oxygen reduction reaction (ORR) on the non-precious metal catalyst, developing transition metal and heteroatom doped carbon materials with abundant active sites and nanoporous structure is crucial but challenging. Herein, a novel FeS-decorated three-dimensional hierarchical porous N, S co-doped carbon catalyst is derived from silica based ionogel, of which 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm][TfO]) acts as source of N and S, and porous silica framework, in suit originated from silicane by sol-gel process, acts as a template to get a large specific surface area (987.5m(2) g(-1)). The obtained catalyst shows excellent ORR activity in 0.1M KOH (positively shifted half-wave potential of 0.87 V), high selectivity (electron-transfer number of 3.99), remarkable stability (only 3mV negative shift of half-wave potential after 5000 potential cycles) and perfect methanol-tolerance effect. The remarkable electrochemical performance of the obtained catalyst is mainly attributed to the well-controlled hierarchical porous structure and homogeneous distribution of highly active sites (N, S-dual-doped carbon, Fe-Nx and/or FeS). (c) 2018 Elsevier Ltd. All rights reserved.

Recently, precious metal-free and heteroatom functionalized carbon materials are widely considered as the promising candidates for oxygen reduction reaction (ORR). However, it is still a challenge to controllably prepare the carbon-based electrocatalysts with desirable activities. Herein, we demonstrate a simple strategy to synthesize the Fe/S/N tri-doped mesoporous carbon (Fe-S,N-C) materials as electrocatalysts for ORR. The resultant Fe-S,N-C catalyst possesses high content of pyridinic N (also including Fe-Nx), graphitic N atoms, thiophene S atoms, and abundant defects, as well as the high surface area and desirable mesoporous microstructure. Thus, in alkaline medium, the Fe-S,N-C shows an expected high ORR activity with a onset potential of 0.95 V and half-wave potential of 0.83 V. Meanwhile, the ORR proceeded on Fe-S,N-C via the four-electron transfer pathway. What is more, the as-prepared catalyst shows excellent electrocatalytic stability and good methanol tolerance, suggesting its potential applications in fuel cells and metal-air battery.

Pt-based nanocrystals with controlled morphologies and structures are one of most promising electro-catalysts for oxygen reduction reaction (ORR). Herein, a facile one-pot wet-chemical method is developed to synthesize Pd@PtNi core-shell nanoflowers (CSNFs) supported on the multi-walled carbon nanotubes (MWNCTs). Brij 58 is demonstrated as a structure-directing agent to generate the nanoflower and ascorbic acid acts as a reductant to form a core-shell structure. By tuning the molar ratio of Pd and Pt, Pd@PtNi/MWCNTs CSNFs show obviously improved ORR activity and durability in alkaline electrolyte compared with PtNi/MWCNTs nanoflowers and commercial Pt/C. The results illustrate that the core-shell structure and porous feature of nanoflower are both beneficial to the enhancement of the catalytic properties. (C) 2017 Elsevier B.V. All rights reserved.