Preparation And Catalytic Performance Characterization Of Cobalt-based Composite Catalysts

With the fast development of economy and society,people gradually pay more attention to the resources and environment.The increasing of energy demand and the problem of climatic changes caused by the use of fossil energy are two global problems today.The fossil fuels are limited,and the reduction of oil improves the uncertainty of oil prices.Price fluctuations affect the international energy security and economic growth.The emission of carbon dioxide and harmful gases increase gradually,and the greenhouse effect and air pollution endanger the living environment of human beings.In this situation,it is important to research a new clean energy with high energy density,green combustion products and ideal combustion efficiency.In this paper,the Co-Ni-Cr-P/?-Al₂O₃,Co@Co₃O₄ and Co-P/Ni foam catalysts were prepared by simple ways,and their catalytic applications were investigated respectively.The main content includes the following points:?1?The Co-Ni-Cr-P alloys were synthesized on?-Al₂O₃ through electroless deposition method.The hydrolysis of NaBH₄ was used as a test reaction to measure the catalytic performance.The preparation conditions,such as chromium content?deposition time,and test conditions,such as reaction temperature?NaOH?Na BH₄concentration,were investigated respectively to study the impact on the catalytic performance.The experimental results show that the catalysts electroless deposited for240 s with 0.8 g?L^-1 chromium nitrate concentration own excellent catalytic properties.Its Chemical formu is Ni₁Co_2.44Cr_1.2P_1.03,and the specific surface area is 228.4 m²?g^-1.Moreover,BJH adsorption pore size distribution map shows that the average pore size of Co-Ni-Cr-P alloy catalyst is 5.64 nm.As the concentration of chromium nitrate is0.6 g?L^-1,the hydrogen generation rate of Co-Ni-Cr-P at 40?is about 1.5 L?g^-1?min^-1,and the lower activation energy is 45.96 kJ?mol^-1.?2?The micron sized Co powder sygnised via chemical oxidation method,and the core-shell structure Co@Co₃O₄ composite catalysts prepared by different oxidation methods.we studied the affect of oxidation and annealing temperature on the catalytic performance of Co@Co₃O₄ for hydrogen released in sodium borohydride.The experimental results show that the core shell structure Co@Co₃O₄ catalyst prepared with sodium borohydride as reducing agent has high catalytic activity after annealing at 350?.When the concentration of NaOH is 10%and the concentration of NaBH₄ is4%,the rate of hydrogen production in alkaline sodium borohydride solution at 40?is 11 L?g^-1?min^-1.Moreover,the Co@Co₃O₄ catalyst has certain magnetism,which facilitates the separation and collection of the catalyst after the reaction.This overcomes the disadvantage of powder sample being difficult to recover.?3?Co-P alloy catalysts was successfully loaded on the nickel foam by electroless deposition.In this chapter,the influence of the preparation conditions on the Co-P/Ni foam catalytic performance was investigated.The experimental results show that the coating of Co-P alloy on the foam nickel substrate can significantly improve the catalytic efficiency.When the electroless deposition time is 10 min,the overpotential of OER is about 306 mV,and the slope of Tafel is 51.1 mV?dec^-1.EIS shows that the catalyst has smaller impedance.In the two electrode test system,the catalytic potential of the current density of 10 mA?cm^-2 is 1.67 V.The Co-P/Ni foam composite catalyst showed excellent stability.After 25 h stability test,the morphology of the coating changed from granular to rod-like and didn't fall off,which proved the excellent adhesion between the coating catalyst and the substrate.