Nitrogen-doping Nickel/Carbon Composite Nanofiber Catalysts Foralkaline Fuel Cells

In the past few decades，non Pt-based catalyst materials has been widely studieddue to the low cost and excellent catalytic activities and high chemical andelectrochemical stability. At present, supported nickel and its alloy is commonly usedin alkaline fuel cell (AFC), but under the condition of high oxidation, high watercontent, high temperature, and high voltage in AFC, the support carrier materials ofsuch metal catalysts are highly susceptible to corrosion, resulting in the performanceloss of the catalyst, and further affecting the whole performance of fuel cells. Thus,widespread attention have been received for one-dimensional nanomaterials. Theexperimental results and conclusions are summarized as following:1) One-dimensional PVP/Ni(NO3)2nanomaterials was prepared using theelectrospinning technology. Also to obtain high quality PVP/Ni(NO3)2nanomaterials,the parameters of electrospinning was investigated and optimized, such as the liquidratio, the intensity of electric field and the electric propulsion speed. Scanningelectron microscopy (SEM) were used to characterize the morphology and structureof the prepared nanomaterials. The results show that the best mass fraction of nickelnitrate and polyvinylpyrrolidone was3wt%and15wt%, respectively, with the electricfield intensity of1.67KV/cm and the electric propulsion speed of300ul/h.2) The prepared PVP/Ni (NO3)2nanofibers was treated in pure Ar and5%H2atmosphere in turn to achieve the catalytic Ni/C nanofibers. After further hightemperature treatments in ammonia the nitrogen-doped Ni/C catalyst was obtained.Also, SEM, Transmission Electron Microscopy(TEM), X Ray Diffraction(XRD) andX-ray photoelectron spectroscopy(XPS) measurements were carried out tocharacterize the morphology and structure of the catalyst fibers.3) By using electrochemical methods (such as cyclic voltammetry and linearsweep voltammetry), we compared several catalysts’ oxygen reduction activities.The initial potential, half-wave potential and limiting current of Ni-N/C catalyst is0.025V,-0.13V,-2.91904A respectively. The electron number of ORR reaction is 2.99, proving that the oxygen reduction reaction of Ni-N/C is a two-and four-electron mixed reaction. The catalytic activity of Ni-N/C is better than that of Ni/Cnanofibers with a two-electron reaction. For the nitrogen-doped Ni/C catalyst,although it lost its original surface structure, its oxygen reduction activity obviouslyincreased than that of the unmodified Ni/C catalyst, this may be due to the increasedactive sites on surfaces after nitrogen doping.