Preparation Of Nickle-Base Nanomatrials And Their Application Of Hydrogen Oxidation Reaction In Alkaline Electrolytes

In recent decades,with the continuous development of human society,environmental pollution and energy shortage are becoming more and more serious.As a large country of energy consumption,the development of new clean alternative energy in China is particularly urgent.Fuel cell can convert the chemical energy stored in fuel and oxidant into electric energy,and its only by-product is water.It is a kind of green power supply with simple structure,low corrosion and high efficiency and cleanliness.In particular,the development of alkaline anion exchange membrane(AEM)technology in recent years,it avoids the problem of carbonation of traditional fuel cell in alkaline electrolyte and the problem of slow(ORR)reaction rate of cathodic oxygen reduction reaction and the problem that non-Pt-based catalyst can not be used in acidic electrolyte,which makes fuel cells more competitive.However,Pt-based noble metal anode catalysts are still used in fuel cells,which greatly limits the commercialization of fuel cells.Therefore,the development and utilization of efficient and stable non-noble metal catalysts is of great significance.The main content of this thesis is the hydrogen oxidation reaction(HOR)of Ni-based nano-materials as fuel cell anode catalyst in alkaline electrolyte.The research contents include the preparation and characterization of Ni-based catalysts,the effects of catalyst components and supports on HOR performance.Specific research contents are as follows:1.GO was prepared by improved Hummers method.Three catalysts,N-rGO,Ni/rGO and Ni/N-rGO,were prepared from GO by reduction with sodium borohydride and doping N with hydrazine and ammonia.The Ni/N-rGO catalysts were characterized by XRD,SEM and SEM mapping.It was found that the prepared GO was doped with N,the oxygen-containing functional groups were well removed,and the Ni nanoparticles were uniformly distributed on the surface of the N-rGO.Electrochemical tests in 0.1 mol/L KOH electrolyte showed that N-GN had no catalytic activity of HOR.The electrochemical surface areas of Ni/N-rGO catalyst and Ni/rGO catalyst were 2.484 cm~2 and 0.309 cm~2,respectively.Compared with Ni/rGO catalyst,the electrode of Ni/N-rGO catalyst has larger electrochemical surface area,the limit current density is increased by 3.1 times,and the exchange current density is increased by 1.7 times.N-doped graphene can not only stabilize nanoparticles and prevent particle rearrangement,but also improve the catalytic activity of nanoparticles.2.Using nickel nitrate hexahydrate and ammonium metatungstate as raw materials,precursors were prepared according to the atomic ratio of Ni to W at 1:1,3:1,5:1.Thermal reduction was carried out in hydrogen atmosphere.The prepared NiW composites were named NiW=1:1,NiW=3:1,NiW=5:1.The catalytic performance of NiW=1:1 material was the best by electrochemical performance test.Then,graphite oxide(GO)was used as the carrier to compound with the precursor by impregnation method,and NiW/rGO catalyst was obtained by thermal reduction in hydrogen atmosphere.Compared with NiW=1:1 catalyst,NiW/rGO catalyst has faster activation rate and higher HOR catalytic activity in electrolyte.Through the structural characterization and electrochemical tests,it was found that W can improve the oxidation resistance of the catalyst,make the catalyst activated faster,and the NiW/rGO catalyst with larger specific surface area can fully contact with the electrolyte,thus improving the HOR catalytic activity of the catalyst.3.Using nickel nitrate,ammonium metatungstate and ammonium molybdate as raw materials,precursors were prepared according to the atomic ratio of Ni,Mo and W at 1:1:1.NiMoW composite catalysts were prepared by hydrogen thermal reduction of precursors at500 ~oC,550 ~oC and 600 ~oC,respectively.The prepared catalysts were named NiMoW-500,NiMoW-550 and NiMoW-600.The electrochemical tests showed that NiMoW-500 had no HOR catalytic activity.NiMoW-550 catalyst had faster activation rate and higher HOR catalytic activity than NiMoW-600 catalyst in electrolyte.This may be due to the fact that the active component in the precursor is not reduced at 500 ~oC.The catalyst reduced at 600 ~oC is more easily oxidized,which reduces the catalytic performance of the catalyst for HOR.