Design And Performance Investigation Of High Efficiency Catalysts For Formic Acid Dehydrogenation Based On Nitrogen-Containing Molecules Regulated

In the context for the transformation of the world’s energy structure into a low-carbon environment focused on environmental protection,hydrogen energy has the advantages of high production capacity and zero carbon emissions,so it is expected to become one of the main energy sources in the future,but the necks of hydrogen energy application are still concentrated in storage and transportation.Chemical hydrogen storage materials are safer and more efficient than traditional hydrogen storage methods in terms of transportation and hydrogen storage capacity.The theoretical hydrogen storage content of formic acid（HCO₂H,FA）is about 4.4 wt.%,which can be dehydrogenated under the effect of catalysts.Therefore,it is particularly important to develop catalyst that catalyze FA dehydrogenation with high efficiency,and nitrogen doping will improve the catalyst’s performance through size and electronic effect,so that hydrogen（H₂）can be released more efficiently.In this paper,different nitrogen containing molecules were used to modify the catalyst,its catalytic performance of FA decomposition to dehydrogenation was studied:1.Polyethyleneimine（PEI）is a nitrogenous molecule with water soluble.We modified PEI onto graphene（r GO）to obtain the PEI-r GO,and then Au_0.3Pd_0.7/PEI-r GO catalyst was prepared by wet chemical method to loading Au Pd nanoparticles（NPs）onto the PEI-r GO substrate.The catalyst showed excellent catalytic activity in hydrogen production by FA dehydrogenation reaction.At 323 K without any additives,the initial turnover frequency（TOF）is 2357.5 mol _H2·mol^-1_catalyst·h^-1,which is higher than most of the heterogeneous catalysts used to catalyze the dehydrogenation of FA under the same reaction conditions.The catalytic performance is not significantly reduced in the fifth reaction of the cycle experiment,the cycle stability is relatively good.The reasons for the improvement of the above catalyst performance are that,on the one hand,the amino groups carried in nitrogen containing molecules provide anchor points for the attachment of metal NPs,which limit the particle size and increase the numbers of active sites while immobilizing metal NPs.On the other hand,the adjustment of the electronic structure of metal NPs by amino groups promotes the dehydrogenation of FA.2.Tripeptide（TPT）is a green and environmentally friendly small molecule active peptide,which is formed by the condensation of glycine（G）,lysine（L）and histidine（H）.Among them,L and H are basic amino acids essential for the human body,the alkaline environment provided by them can promote the smooth progress of FA decomposition dehydrogenation reaction.Therefore,in this work,basic nitrogen containing molecules such as TPT and amino acids were introduced into nano metal catalysts,and their effects on the geometric structure and electronic structure of metal catalytic active components were investigated.The catalytic activity of the catalyst in FA hydrogen production reaction was optimized by regulating the types and dosage of small molecules nitrogenous substances.The experimental results show that the Pd/C catalyst modified by TPT（Pd/C-TPT）has greatly improved the catalytic activity of FA dehydrogenation under the environment of 323K without additives,and its TOF value is 2101.8 mol _H2·mol^-1_catalyst·h^-1,which is better than most Pd catalysts.The reason for this improvement in catalytic activity is that on the one hand,TPT has a certain limiting effect on the size of metal particles.On the other hand,the amino group from the nitrogenous molecules regulate the electronic structure of Pd NPs.