High pressure pyrolyzed non-precious metal oxygen reduction catalysts for alkaline polymer electrolyte membrane fuel cells

Non-precious metal catalysts, such as metal-coordinated to nitrogen doped-carbon, have shown reasonable oxygen reduction reaction (ORR) performances in alkaline fuel cells. In this report, we present the development of a highly active, stable and low-cost non-precious metal ORR catalyst by direct synthesis under autogenic-pressure conditions. Transmission electron microscopy studies show highly porous Fe-N-C and Co-N-C structures, which were further confirmed by Brunauer-Emmett-Teller surface area measurements. The surface areas of the Fe-N-C and Co-N-C catalysts were found to be 377.5 and 369.3 m2 g-1, respectively. XPS results show the possible existence of N-C and M-Nx structures, which are generally proposed to be the active sites in non-precious metal catalysts. The Fe-N-C electrocatalyst exhibits an ORR half-wave potential 20 mV higher than the reference Pt/C catalyst. The cycling durability test for Fe-N-C over 5000 cycles shows that the half-wave potential lost only 4 mV, whereas the half-wave potential of the Pt/C catalyst lost about 50 mV. The Fe-N-C catalyst exhibited an improved activity and stability compared to the reference Pt/C catalyst and it possesses a direct 4-electron transfer pathway for the ORR process. Further, the Fe-N-C catalyst produces extremely low HO2- content, as confirmed by the rotating ring-disk electrode measurements. In the alkaline fuel single cell tests, maximum power densities of 75 and 80 mW cm-2 were observed for the Fe-N-C and Pt/C cathodes, respectively. Durability studies (100 h) showed that decay of the fuel cell current was more prominent for the Pt/C cathode catalyst compared to the Fe-N-C cathode catalyst. Therefore, the Fe-N-C catalyst appears to be a promising new class of non-precious metal catalysts prepared by an autogenic synthetic method. © The Royal Society of Chemistry 2015.

Photochemically reduced polyoxometalate assisted generation of silver and gold nanoparticles in composite films: a single step route

A simple method to embed noble metal (Ag, Au) nanoparticles in organic–inorganic nanocomposite films by single step method is described. This is accomplished by the assistance of Keggin ions present in the composite film. The photochemically reduced composite film has served both as a reducing agent and host for the metal nanoparticles in a single process. The embedded metal nanoparticles in composites film have been characterized by UV–Visible, TEM, EDAX, XPS techniques. Particles of less than 20 nm were readily embedded using the described approach, and monodisperse nanoparticles were obtained under optimized conditions. The fluorescence experiments showed that embedded Ag and Au nanoparticles are responsible for fluorescence emissions. The described method is facile and simple, and provides a simple potential route to fabricate self-standing noble metal embedded composite films

Nitrogen-doped carbon nanofoam derived from amino acid chelate complex for supercapacitor applications

We report a novel strategy to fabricate the nitrogen-doped mesoporous carbon nanofoam structures (N-MCNF), derived from magnesium amino acid chelate complex (Mg-acc-complex) for its application towards high performance supercapacitor (SCs) system. A series of N-MCNF with well-connected carbon nanofoam structure have been developed by varying the synthesis temperature. The fabricated N-MCNF material possesses a high surface area (1564 m2 g-1) and pore volume (1.767 cm3 g-1) with nitrogen content of 3.42 wt%. A prototypical coin cell type symmetric N-MCNF SC device has been assembled with 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIMBF4] ionic liquid electrolyte, and evaluated for SCs studies. The N-MCNF with high textural properties delivers unprecedented SC performance, such as high specific capacitance (204 Fg-1 at 0.25 Ag-1, 25 °C), high energy density (63.4 Wh kg-1), high power density (35.9 kW kg-1) and long-term cycle life (32,500 cycles). Significantly, N-MCNF materials exhibited high power rate performance, at 500 mV-1 (115 Fg-1) and 25 Ag-1 (166 Fg-1) owing to the uniform mesopore size distribution (∼4 nm). The N-MCNF SC device delivered maximum energy densities of 83.4 and 93.3 Wh kg-1 at 60 °C and 90 °C, respectively. Such outstanding N-MCNF SC device is successfully demonstrated in solar energy harvester applications. © 2016 Elsevier B.V.1

Graphitic Carbon-NiCo Nanostructures as Efficient Non-Precious-Metal Electrocatalysts for the Oxygen Reduction Reaction

Composites of graphitic carbon layers and transition metals or metal alloys have received considerable attention for use as non-precious-metal catalysts for ecofriendly energy devices. In this paper, we report graphitic carbon-supported NiCo alloys (NiCo at GC) that function as non-precious-metal electrocatalysts for the oxygen reduction reaction under alkaline conditions. In particular, we examined the effect of the pyrolysis temperature on the oxygen reduction activity. The catalyst prepared at 600°C provided an oxygen reduction half-wave potential (E1/2) of 0.81V - only 10mV less than that of a commercial Pt/C catalyst (0.82V) - with the transfer of almost four electrons. Structural and chemical studies indicated that the excellent activity and stability of the NiCo at GC catalysts resulted from the strong interactions between (and the combined effects of) the metal and the carbon, dictated by the annealing temperature. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.1

Mesoporous Co-CoO/N-CNR nanostructures as high-performance air cathode for lithium-oxygen batteries

A bifunctional air cathode for the electrochemical oxygen reduction and evolution in a Li-O2 battery comprising Co-CoO nanoparticles embedded in the nitrogen-doped carbon nanorods (Co-CoO/N-CNR) is presented. The nanorod morphology with mesoporous nanostructures can handle continuous formation and decomposition of Li2O2 and favors the transport of electrons and ions, therefore improves the rate capability and cycle stability. Moreover, the hierarchical mesoporous Co-CoO/N-CNR reduces the overall overpotential over the cycle and decreases the side reaction between Li2O2 and carbon surface, leading to a significant enhancement of the specific capacity and cycling capability. With the cooperative effect of Co-CoO/N-CNR and porous nature, Co-CoO/N-CNR cathode delivers a high discharge specific capacity of 10,555?mAh?g?1 at 100?mA?g?1 and long cycle stability for over 86 cycles without any capacity loss at a high cutoff capacity of 1000?mAh?g?1. Furthermore, excellent performance of 7514?mAh?g?1 at 500?mA?g?1 is achieved. ? 2017 Elsevier B.V.

Nitrogen-doped arch and hollow shaped nanocarbons for CO2 adsorption

We report arch and hollow nanocarbons with high nitrogen content and appreciable surface area that are highly capable of adsorbing CO2 (4.23 mmol g-1), are selective (CO2/N2: ∼13%) and have high facile regeneration properties (98%) under ambient conditions, respectively. © The Royal Society of Chemistry 2014.FALS

Polyoxometalate Reduced Graphene Oxide Hybrid Catalyst: Synthesis, Structure, and Electrochemical Properties

The deposition of polyoxometalate (POM) on chemically reduced graphene oxide sheets was carried out through electron transfer interaction and electrostatic interaction between POM and graphene sheets to make a heterogeneous catalyst in aqueous media. Well dispersed individual phosphomolybdic acid (PMo) clusters were observed by electron microscopy and atomic force microscopy measurements. The interaction between polyoxometalate and the graphene sheet was confirmed by using various spectroscopic methods such as FT-IR, UV-vis, and Raman. The UV-visible, IR, and cyclic voltammetry results revealed alteration of the electronic structure of deposited PMo as a result of strong interaction with the graphene oxide surface. Electrochemical properties of the PMo-rGO catalyst were investigated in an aqueous acidic electrolyte. The hybrid catalyst showed enhanced electro-oxidation of nitrite compared with pure homogeneous PMo and rGO. © 2013 American Chemical Society.1