Study On Preparation And Properties Of Ni-C Powders As Electro-catalyst

Ni-C powders as electro-catalyst for hydrogen evolution were prepared efficiently by utilizing the interaction between PE/PP and NiO/Ni2O3 powders.The reaction mechanism between PE/PP and NiO/Ni2O3 was systematically investigated.The gaseous products were analyzed by using GC-MS connected to TG analyzer.And the solid products were analyzed the crystal structure,micro-morphology,carbon content and electro-catalytic performance for hydrogen evolution from NaOH(1M)aqueous solution.The influences of raw materials,mixing ratio of plastics to nickel oxide and temperature on the properties of Ni-C powders were investigated to optimize the experimental conditions for fabricating Ni-C catalyst of high performance.The conclusions can be summarized as the followings.(1)When the mixtures of PE/PP and NiO/Ni2O3 are heated,the following changes occur step-wisely plastics melting(PE/PP),pyrolysis of plastics(PE/PP)and reduction of nickel oxide(NiO/Ni2O3)by reducing agents originated from the plastics.Two separate stages of weight loss are recorded.In the case of NiO,corresponding to the reduction of NiO by hydrogen and carbon;while only one weight loss stage can be observed in the case of Ni2O3.With increasing nickel oxide content in raw material mixtures,the onset and end temperatures of reactions decrease.(2)The products originated from PE/PP and NiO/Ni2O3 reactions include gaseous and solid phases.The gaseous products contain mainly hydrogen and organic volatiles such as methane etc.from pyrolysis of plastics,and water,carbon monoxide and carbon dioxide as the results of nickel oxide reduction.The solid products are mixtures of nickel and carbon powders.(3)With increasing NiO/Ni2O3 content in PE/PP and NiO/Ni2O3 mixtures,the catalytic performance of Ni-C powder improves first to the best level and then decays.The most suitable mixing ratio is around 1:2.5 of plastics to nickel oxide to enable Ni-C powders the highest electro-catalytic performance in the current study.(4)With increasing fabrication temperature the electro-catalytic performance of Ni-C powders deteriorates due to the enhancement of nickel powder agglomeration.(5)Ni-C powders manufactured from PP+Ni2O3 mixtures exhibit the best catalytic result,followed by the ones from PE+NiO and PE+Ni2O3 mixtures,and the last ones from PP+NiO.This is determined mainly by the particle size of Ni-C powders.(6)Ni-C powders fabricated in the current study with best catalytic performance is superior to Pt plate and show very good stability for hydrogen evolution from basic solution.There is almost no difference between the over-potential measured at the first cycle and that of the 1000th cycle,indicating that Ni-C powders can be expected a long service life.