Preparation Of Carbon Supported Nickel Metal Catalysts And Studies On Ethanol Oxidation Performance

The direct ethanol fuel cell(DEFC)is a promising energy source because of high energy conversion efficiency,low pollutant emission and good stability of DEFC as well as the easy accessibility of ethanol.Although DEFC is a promising candidate of new power systems,the expensive catalysts of noble metals inhibit its large scale applications.So designing novel,effective and cheap catalysts is presently a paramount challenge to replace the expensive noble metal catalysts.This papermainly uses the nitrogen doped carbon with different nickel morphology catalysts have been prepared,and study the effects of nitrogen doping and the performance of the catalyst,the catalysts for ethanol oxidation were prepared:N-doped carbon encapsulated nickel nanoparticles(NiNC)are rationally and readily prepared from mixtures of nickel salt,glucose and urea by a simple heating route.The elevated viscosity of the mixtures inhibits the migration of Ni species to form highly dispersive and very small Ni nanoparticles.The particle sizes are tuneable by adjusting the composition of the raw mixtures.Heat treatment transforms glucose into porous active carbon.The addition of urea produces plenty of N-containing groups in the carbon matrix.The optimized sample of NiNC-4 contain small Ni nanoparticles of 2.02 nm in size,large surface area of 400.7 m2g-1 and high nitrogen content of 7.21 at%.Fitting the XPS data derives a high proportion of N-6(pyridinic N),and N-5(pyrrolic N or pyridinic-N).The porous carbon matrix,small nanoparticle size,and the abundant N-containing groups render NiNC-4 an excellent electrocatalytic performances for ethanol oxidation.An ultrahigh current density of 327 mA cm-2 achieves in 0.1 M NaOH solution with 1 M ethanol by using NiNC-4 as the electrocatalyst.NiNC-4 electrode also exhibit a good long-term cycling stability.89%of the initial current densities sustain in 0.1 M NaOH solution with 0.5 M ethanol after 500 cycles.96.8%of the initial current density recover by moving the NiNC-4 electrode into fresh 0.1 M NaOH solution with 0.5 M ethanol after 500 cycles.The excellent electrocatalytic properties of NiNC-4 for ethanol oxidation stems from the synergistic effect of porous carbon substrate,abundant N-containing groups and small nickel nanoparticle size.N-doped activated carbons with controllable Ni nanorods(NiNC')catalysts were fabricated by a facile one-pot method for electrocatalytic oxidation of ethanol.The effects of carbon source and Ni precursor for the different microstructures of the forming Ni are discussed in this work.The sucrose and chloride ion are the key factors for forming nanorod-like nickel catalyst.The sizes of Ni nanorods can be controlled by the reactant ratios and influence the catalytic performance for ethanol oxidation.The doped N atoms are also used to improve the catalytic performance for ethanol oxidation.The NiNC'-3 catalyst with the proper content and size of Ni exhibits an improved catalytic activity toward ethanol oxidation with a 5 times current density and 16 times rate constant in comparison with the NiNC'-1 catalysts.A current density of 47.5 mA cm'2 is generated on NiNC'-3 electrode.Furthermore,current density retention of 80.7%suggests an excellent cyclic stability after 1500 cycle on the NiNC'-3 electrode.All of these elevated performances can be attributed to the relatively uniform nanorods size,as well as the excellent electrical conductivity and stability of the carbon support.