Hydrogen Preparation From NaBH₄ And Reduction Of P-Nitrophenol Catalyzed By Carbon Nitride Supported Pd-Au-CoB Multiparticles

As a new type of photocatalytic material,carbon nitride has attracted much attention in recent years.It can be used as catalyst carrier in different catalytic systems.Using the Mott-Schottky effect of carbon nitride materials,the catalytic activity of active metal particles can be significantly improved through the active matching of active metal composites between the conductive band and the forbidden band of carbon nitride materials.However,the small specific surface area of traditional carbon nitride materials limits its efficient application in supported catalysts.In this paper,a kind of high specific surface area composite carbon nitride material was synthesized,and then a supported catalyst with precious metal micro-doping was prepared by using the composite carbon nitride material.The catalytic activities of the catalyst in hydrogen production by sodium borohydrate and reduction of p-nitrophenol were systematically studied.The main research results are as follows:（1）In this thesis,based on the amorphous carbon and carbon nitride combined strategy,the amorphous carbon-carbon nitride composite materials（AC-C₃N₄）can be prepared by EDTA-citric acid complexing method.The introduction of the amorphous carbon with high specific surface area significantly increases the specific surface area of composite carbon nitride materials.The study shows that the optimized carbon nitride composites exhibit the higher specific surface area of 68.3 m~2.g^-1,the pore volume of 7.1×10^-2cc.g^-1 and the average pore size of 4.1 nm.Compared with traditional carbon nitride materials with low specific surface area such as several square meters,the specific surface area of composite carbon nitride can be improved by nearly five times.In this theisis,the crystal phase,morphous state and chemcial composition of the composite carbon nitride were studied systematically.Finally the optimial synthesis strategy of the composite carbon nitride material can be obtained.（2）Pd-Au-Co B/AC-C₃N₄ supported catalyst was prepared based on composite carbon nitride（Ac-C₃N₄）material with high specific surface area.The characterization results show that the active components of Pd,Au and Co can be highly dispersed onto the composite carbon nitride carrier.TEM analysis shows that the particle size of Co,Pd and Au nanoparticles is less than 5nm,and some of the nanoparticles are even smaller than 1.0nm.No aggregation of active components can be observed.XPS and HRTEM analysis showed that Co B nanoparticles can be distributed onto the composite carbon nitride carrier with amorphous structure,while Pd/Au nanoparticles or their alloy particles are highly dispersed among the active components of cobalt boride.Therefore,the active components of precious metals prepared in this paper show the characteristics of high dispersion.XPS analysis showed that the active components of transition metal or noble metal can be adsorbed onto nitrogen atoms in C₃N₄ significantly.Hence,the active metal particles exhibit highly dispersed properties on the catalyst supports.（3）Based on sodium borohydride hydrolytic hydrogen production system,the catalytic activity of Pd-Au-Cob/AC-C₃N₄ supported catalyst for hydrogen production was systematically investigated in this thesis.The experimental results show that the hydrogen production rate of sodium borohydride based on the Co B/AC-C₃N₄ catalyst is about 25.56m L.min^-1.g^-1,and the highest catalytic activity of the Pd-Au-Co B/AC-C₃N₄supported catalyst is about 141.71 m L.min^-1.g^-1（based on the overall weight calculation of the catalyst）after the optimization.It can be concluded that the precious metal doping can significantly improve the catalytic activity of the catalyst.Systematic experiemntal analysis showed that the improved catalytic activity of Pd-Au-Co B/Ac-C₃N₄ supported catalyst is mainly attributed to the synergistic effects between Pd,Au and Co B.Meanwhile,Pd-Au-Co B/AC-C₃N₄ supported catalyst and sodium borohydride hydrogen molecular system was used to chemical reduce p-nitrophenol to produce p-aminophenol.Our catalysts also showed high catalytic activity in p-nitrophenol reduction reaction.