Preparation Of Porous Carbon-supported Palladium-based Catalysts Derived From Biomass And Their Catalytic Properties For Hydrogen Production From Formic Acid Decomposition

With the development of society,people’s demand for energy is increasing day by day.However,traditional energy sources such as fossil fuels,which are heavily relied on at present,are non-renewable energy sources.Therefore,the development of new clean renewable energy is extremely urgent.Hydrogen energy is an ideal energy carrier because of its abundant reserves,high energy density and pollution-free combustion products.However,hydrogen（H₂）is a gas at room temperature and pressure and has a low volume energy density,which makes it difficult to store and transport hydrogen in practical production,thus limiting the large-scale application of hydrogen energy.Formic acid can be used as a good hydrogen storage material because of its high hydrogen content（4.4wt%）,high mass energy density,non-toxic,wide range of sources,liquid at room temperature and excellent stability.Formic acid can be broken down in two ways,one to produce H₂and CO₂,the other to produce H₂O and CO.Therefore,it is very important to develop high performance catalyst to promote H₂production and inhibit CO production.Supported palladium（Pd）based nanoparticles（NPs）catalysts have been paid much attention because of their good catalytic activity and H₂selectivity for the decomposition of formic acid to hydrogen production.The support plays an important role in the high performance of the supported catalyst.Peanuts and corn are economic crops planted in large quantities,and how to deal with the peanut shell and corn cob has become a big problem.If these agricultural wastes are properly treated,carbon materials with porous structure can be obtained,which can be used as the carrier of catalyst and has great significance.Based on the above background and research situation,this paper uses peanut shell and corn cob as raw materials to prepare nitrogen-doped porous carbon materials by high temperature carbonization,and develops nitrogen-doped porous carbon materials supported by Pd-based nanoparticles as catalysts for the decomposition of formic acid to produce hydrogen.The main research consists of the following three parts:1.Nitrogen doped porous carbon（N-C）was prepared by high temperature annealing method using corn cob powder as precursor.Using N-C as the support,Pd²⁺in Na₂Pd Cl₄solution was reduced by liquid phase reduction method to obtain Pd NPs,and Pd/N-C catalyst was obtained by loading the Pd NPs on N-C.Pd NPs was uniformly dispersed on N-C support with small particle size（6.9±3.2 nm）.Among them,the Pd/N-C catalyst obtained from corn cob powder after growing Pd NPs on N-C carrier annealed at 800℃has the best catalytic activity,and its TOF value can reach 732 h^-1at 30℃,and has good cyclic stability.According to its experimental results at different reaction temperatures,its activation energy in this reaction can be calculated as 22.19 KJ/mol by Arrhenius formula.2.The performance of single metal catalyst still cannot meet the actual demand of hydrogen production from formic acid,so this chapter designed Au Pd bimetallic catalyst.Using peanut shell powder as precursor,nitrogen doped porous carbon（N-C_p）was prepared by high temperature annealing method as carrier.Au_xPd_1-x/N-C_pcatalysts were obtained by reducing Au³⁺and Pd²⁺in HAu Cl₄and Na₂Pd Cl₄to Au NPs and Pd NPs,respectively,which formed alloy phase and then supported on N-C_pcarrier.Through multiple groups of comparison experiments,we found that the carrier plays an important role in the performance of Au Pd NPs,and the TOF value of Au_0.5Pd_0.5/N-C_pis 3.9 times of that of Au_0.5Pd_0.5under the same conditions.The peanut shell derived N-C_psupported catalysts showed higher activity than commercial carbon（C）and corn cob derived N-C supported catalysts,and 800℃was still the best annealing temperature for N-C_psupported catalysts.The ratio of Au to Pd has a great influence on the performance of the catalyst.When the ratio of Au to Pd is 1:1,that is,Au_0.5Pd_0.5/N-C_phas the best performance.The TOF value of Au_0.5Pd_0.5/N-C_pin the hydrogen production reaction of formic acid decomposition at room temperature is as high as 2118 h^-1,and has good cyclic stability.3.In order to reduce the preparation cost of the catalyst,the transition group non-noble metal nickel（Ni）was used to replace the precious metal Au,that is,Ni and Pd were combined into Ni_xPd_1-x/N-C_pcatalyst,and the total molar amount of active metal remained unchanged（0.02 mmol）in the experiment.The results show that the Ni_xPd_1-x/N-C_pcatalyst also has excellent catalytic performance in the hydrogen production reaction of formic acid decomposition,and the best catalyst is Ni_0.4Pd_0.6/N-C_p,whose TOF value is 2019 h^-1at room temperature and without additives.It can be known that the activation energy required for the hydrogen production reaction of formic acid decomposition in this experiment is 18.42 KJ/mol.After five cycle stability tests,Ni_0.4Pd_0.6/N-C_pcatalyst still has good catalytic activity for hydrogen production from formic acid.