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A Fe-Co dual-metal co-doped N containing the carbon composite (FeCo-HNC) was prepared by adjusting the ratio of iron to cobalt as well as the pyrolysis temperature with the assistance of functionalized silica template. Fe1Co-HNC, which was formed with 1D carbon nanotubes and 2D carbon nanosheets including a rich mesoporous structure, exhibited outstanding oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activities. The ORR half-wave potential is 0.86 V (vs. reversible hydrogen electrode, RHE), and the OER overpotential is 0.76 V at 10 mA cm−2 with the Fe1Co-HNC catalyst. It also displayed superior performance in zinc–air batteries. This method provides a promising strategy for the fabrication of efficient transition metal-based carbon catalysts. [ABSTRACT FROM AUTHOR]

The design of highly efficient and stable electrocatalysts for oxygen reduction reaction (ORR) is still a great challenge. Herein, we prepared Co,N-codoped carbon nanocomposites (Co@NC-ZM) with entangled carbon nanotubes. The large Brunauer–Emmett–Teller surface area (604.7 m2 g−1), rich mesoporous feature, Co,N doping and synergetic effect between various species of Co@NC-ZM can expose more active sites and facilitate conductivity and mass transport. Benefiting from the above unique advantages, Co@NC-ZM exhibits excellent ORR performance with more positive onset potential (0.96 V) and half-wave potential (0.83 V) than those of commercial Pt/C (0.96 and 0.81 V, correspondingly). This work provides a new strategy for further exploring efficient non-precious-metal-based catalysts for ORR. [ABSTRACT FROM AUTHOR]

This report presents a simple method to produce an ultrasmall-Fe7C3/N-doped porous carbon hybrid (u-Fe7C3@NC) as an excellent oxygen reduction reaction (ORR) electrocatalyst. A zinc–air battery assembled with u-Fe7C3@NC performs at a higher open potential (1.486 V) and at a lower discharge overpotential compared with the commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

This study presents an in situ route to produce 3D Fe–N doped metal organic framework@carbon nanotubes/graphene (Fe-MOF@CNTs-G) hybrids as efficient oxygen reduction reaction (ORR) catalysts in both basic and acidic solutions. A rechargeable zinc–air battery assembled with Fe-MOF@CNTs-G exhibits a lower charge/discharge overpotential than the commercial IrO2 + 20% Pt/C catalyst. [ABSTRACT FROM AUTHOR]

The design of efficient mixed Mn–Co oxides as oxygen reduction reaction (ORR) electrocatalysts in alkaline media has been boosted nowadays. Recently, multivariant MOFs have been demonstrated as versatile precursors to construct these mixed metal oxides. Herein, we synthesized four mixed Mn–Co oxide samples via simply annealing their MIL-53 precursors with different Co/Mn molar ratios. These four samples were dominated by three kinds of Mn–Co spinel phases. The mixed Mn–Co oxides showed enhanced ORR performances compared with the single metal counterparts in alkaline media. In particular, the sample containing a pure MnCo2O4 phase exhibited the highest activity with a half-wave potential of 0.772 V (vs. RHE), only 40 mV negative compared with that of commercial Pt/C. The H2O2 yield was calculated to be below 12.1%, corresponding to the high diffusion-limited current density along with the high electron transfer number. The surface defects, active Mn4+/Mn3+ and electrochemically active surface area together affected the ORR performances of these mixed Mn–Co oxides. The present work highlights the facile controllability of divalent MIL-53 analogues for highly efficient mixed Mn–Co oxides in ORR electrocatalysis. [ABSTRACT FROM AUTHOR]

A Co–N doped 3D carbon microsphere/nanofiber hybrid was produced by electrospinning. We can effectively control the morphology transformation from a pearl necklace-like nanofiber to a microsphere/nanofiber hybrid. The hybrid shows Pt-like oxygen reduction reaction activity both in acidic and basic solutions, making it one of the best non-noble metal oxygen catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] In this work, potassium acetate (KAc) was added during the synthesis of a Zn-Fe based metal-organic framework (Fe-ZIF-8) to increase the fixed amount of Fe while simultaneously enhancing the number of pores. Electrospinning was utilized to embed KAc-modified Fe-ZIF-8 (Fe-ZIF-8-Ac) into the polyacrylonitrile nanofiber mesh, to obtain a network composite (Fe@NC-Ac) with hierarchical porous structure. Fe@NC-Ac was co-pyrolyzed with thiourea, resulting in Fe, N, S co-doped carbon electrocatalyst. The electrochemical tests indicated that the prepared catalyst displayed relatively remarkable oxygen reduction reaction (ORR) catalytic activity, with an onset potential (E onset) of 1.08 V (vs. reversible hydrogen electrode, RHE) and a half-wave potential (E 1/2) of 0.94 V, both higher than those of the commercial Pt/C (E onset = 0.95 V and E 1/2 = 0.84 V), respectively. Assembled into Zn-air batteries, the optimized catalyst exhibited higher open circuit voltage (1.698 V) and peak power density (90 mW cm−2) than those of the commercial 20 wt% Pt/C (1.402 V and 80 mW cm−2), respectively. This work provided a straightforward manufacturing strategy for the design of hierarchical porous carbon-based ORR catalysts with desirable performance. [ABSTRACT FROM AUTHOR]

Exploring highly active non-noble metal oxygen reduction reaction (ORR) catalysts and understanding the mechanism are very essential for future energy conversion and storage devices. Herein, we provide a novel method to produce FeP nanoparticles and single atom Fe co-doped porous hollow carbon hybrids (FeP@SA-Fe/HC) from iron metal–organic framework (NH 2 -MIL(Fe)), phytic acid and melamine. Interestingly, thanks for the co-existence of the atomic Fe and FeP nanoparticles, porous hollow microstructure, and heteroatom doping, the obtained FeP@SA-Fe/HC-900 hybrid shows very high ORR activity with a more positive half-wave potential of 0.843 V (vs. reversible hydrogen electrode) in 0.10 M KOH, comparing with the commercial 20 wt% Pt/C catalyst (0.807 V). Our methodology puts forwards a new sight to enhance the electrochemical catalytic performance of carbon composite materials through the synergistic effect of the atomic-metal and metal nanoparticles. [ABSTRACT FROM AUTHOR]

The development of transition metal nitrides/carbon hybrids with well-organized morphology, outstanding efficiency and durability for Zn-air batteries are of great urgency. Herein, a morphology-controlled strategy to efficiently fabricate uniform Co 4 N nanoparticles anchored on N -doped carbon (Co 4 N@NC-m) is reported. The diameters and distribution of Co 4 N nanocrystals can be tuned to be homogeneous profited by abundant N sources in melamine. Moreover, thanks to the advantages of higher nitrogen doping content, better electrical conductivity, higher degree of graphitization, and larger electrochemical surface area, Co 4 N@NC-m possesses excellent oxygen reduction reaction (half-wave potential of 0.87 V) and oxygen evolution reaction (overpotential of 398 mV at 10 mA cm−2) activities in basic solution. The Zn-air battery fabricated with Co 4 N@NC-m owns higher open circuit voltage (1.490 V), larger power density, and better rechargeability than those of the commercial IrO 2 + 20% Pt/C catalysts, which proves the potential application in practical energy conversion devices. A novel strategy was proposed to design morphology-controlled Co 4 N nanocrystals deposited on N -doped carbon as high-efficient and durable air cathode catalysts for rechargeable Zn-air batteries, which provides new thoughts for developing non-noble metal catalysts for clean energy conversion devices. Image 1 [ABSTRACT FROM AUTHOR]

Heteroatom doped carbon based hierarchical nanostructures are one of most interesting electrode materials for boosting oxygen reduction reaction (ORR) owing to the active electronic structure and appealing structural stability. Herein we demonstrated a 'polymerization-dissolution' method to prepare a highly stable Fe, N, S tri-heteroatom doped core-shell carbon (HCSC) nanostructural ORR catalyst. The unique advantages, including the uniformly dispersed N, S and Fe–N active sites, and the special leaf-like core-shell nanostructure, endow the optimized HCSC catalyst (HCSC-IV-H) owning high-efficient ORR activity. Moreover, a Zn–air battery assembled with HCSC-IV-H exhibits a higher open potential (1.430 V) and lower discharge overpotential, comparing with the commercial IrO 2 + 20% Pt/C catalyst. The present work highlights a novel strategy to construct highly efficient heteroatom doped nano-carbon materials for renewable energy storage and conversion devices. A 'polymerization-dissolution' method that regulates the balance between aniline polymerization and iron metal–organic framework dissolution is provided to prepare different kinds of Fe, N and S co-doped carbon core-shell composites. The optimized hybrid electrocatalysts show excellent ORR catalytic activity and high performance for Zn-air batteries. The detailed analysis on such kinds of catalysts reveals that the uniformly dispersed Fe–N sites, synergistic effect of N and S, and special leaf-like core-shell nanostructure are essential to the excellent ORR activities. Image 1 [ABSTRACT FROM AUTHOR]

This paper describes the preparation, characterization, and electrochemical properties of a porous dual-doped carbon composite. The composite is prepared by electrospinning of polyacrylonitrile solution with graphene oxide, and then incipient impregnating with Fe(NO 3 ) 3 solution followed by calcination in N 2 atmosphere. The structure and composition of the composite are characterized by scanning electron microscopy, nitrogen adsorption isotherms, X-ray photoelectron spectroscopy, surface-enhanced Raman scattering, and X-ray diffraction, respectively. Under the optimal conditions, the resultant composite modified electrode exhibits excellent tolerance of methanol crossover, high current density (5.30 and 6.04 mA cm −2 in alkaline and acidic solutions) and good durability (∼92.3% and 79.4% after 10,000 s in alkaline and acidic solutions, respectively) toward oxygen reduction reaction (ORR). Remarkably, the modified electrode displays a four-electron transfer process for ORR. These above excellent electrocatalytic activity of the composite should be attributed to the synergistic effect of planar-N (pyridinic and pyrrolic N), Fe-containing nanoparticles and reduced graphene oxide. [ABSTRACT FROM AUTHOR]

• A hierarchical CC/Co@C-CNTs composite was prepared by DCDA-assisted pyrolysis. • CC/Co@C-CNTs-800-0.10 offers large active area and abundant Co/Co-N x active sites. • The Co/Co-N x species play major role in the catalytic reduction of H 2 O 2. • The H 2 O 2 sensor exhibits high sensitivity and low detection limit. • The sensor can be used for in situ detection H 2 O 2 secreted from living cancer cells. In this work, self-supporting hierarchical Co-embedded N-doped carbon structures composed of leaf-like carbon sheets arrays and interconnected carbon nanotubes (CNTs) were synthesized on carbon cloth (CC) via dicyandiamide-assisted pyrolysis. The resultant composite is abbreviated as CC/Co@C-CNTs, in which Co nanoparticles are embedded both in carbon sheets and the tips of CNTs. The characterizations proved the hierarchical three-dimensional structure, large electroactive surface area of 4.71 cm−2, fast electron transfer, abundant Co/Co-N x active sites, and synergistic effect between Co/Co-N x species and CNTs in the CC/Co@C-CNTs-800-0.10 electrocatalyst. Benefiting from these unique superiorities, the CC/Co@C-CNTs-800-0.10 freestanding electrode exhibits excellent sensing performances of H 2 O 2. It possesses a high sensitivity (388 μA mM-1 cm−2), fast response within 4 s, low detection limit (0.27 μM, S/N = 3) and wide linear range (0.40 μM–7.2 mM). More importantly, the freestanding electrode can be used to in situ detect H 2 O 2 released from MDA-MB-231 cells and HeLa cells. This work provides a new design of nonenzymatic electrochemical sensing platform for amperometric determination of H 2 O 2 in biological environment, which has great potential in cancer diagnosis, environmental monitoring and food analysis. [ABSTRACT FROM AUTHOR]

Due to the obstacle of sluggish kinetics on cathode of fuel cells and metal–air batteries, developing low-cost and durable electrocatalysts to replace the platinum-based catalysts still remains a grand challenge. Here, we describe a simple self-template approach to synthesize N-doped mesoporous carbon nanocages (FeCo@NC) embedded with FeCo alloy nanoparticles as oxygen reduction reaction (ORR) electrocatalyst. The resulting heterostructure is derived from corresponding PBA@PPy composites, which are pre-prepared by polymerization of polypyrrole (PPy) layer on Prussian blue analogue (PBA) nanocubes. The FeCo alloy nanoparticles with an average particle size of ∼10 nm are well dispersed and confined within the shell of carbon nanocages. Benefiting from the mesoporous structure and the synergetic interaction of binary metals, the optimized FeCo@NC-3-800 electrocatalyst exhibits comparable ORR performances (0.83 V for half-wave potential (E 1/2), 5.323 mA cm−2 for limiting current density (J k)), superior durability and excellent methanol tolerance to the commercial Pt/C (20 wt%). This work provides an appropriate strategy for general, efficient and practical synthesis of more promising non-precious metal electrocatalyst with high ORR activity. Image 1 • A simple approach is developed to synthesize N-doped mesoporous carbon nanocages embedded with FeCo alloy nanoparticles. • The FeCo alloy nanoparticles (∼10 nm) are well dispersed and confined within the shell of carbon nanocages. • The optimized FeCo@NC-3-800 electrocatalyst exhibits highly activity and stability towards oxygen reduction reaction. [ABSTRACT FROM AUTHOR]