Preparation And Properties Of PD-based Catalyst For Dehydrogenation Of Formic Acid

Hydrogen is one of the best energy carrier to replace traditional energy sources.Its high combustion value and non-toxic products make it particularly suitable for use in proton membrane fuel cells.The key factor limiting the large-scale application of hydrogen energy is the lack of safe and efficient hydrogen storage technologies.As an intermediate product of microbial processes,formic acid?FA?has the advantages of high hydrogen storage efficiency,large volume energy density,wide sources and high safety.The spontaneous dehydrogenation efficiency of formic acid is extremely low at room temperature,and it is easy to produce CO by-products.The development of highly efficient heterogeneous catalysts is particularly important for the realization of formic acid hydrogen production process.In this paper,Pd/NH₂-rGO,PdAgB/rGO and PdAg/NH₂-TNS-rGO catalysts are successively prepared and use to catalyze the dehydrogenation of FA at room temperature.The NH₂ functionalized graphene oxide is used as support to prepare Pd/NH₂-rGO catalyst.Its physical and chemical properties are characterized by XRD,TEM,XPS and FT-IR.It is found that the metal is dispersed well on the support and the particle size is relatively small.The prepared catalyst has excellent hydrophilic properties.The catalytic performance of dehydrogenation of formic acid at room temperature is studied,and it is found that the Pd/NH₂-rGO catalyst has 100%hydrogen selectivity and high catalytic activity for formic acid dehydrogenation.However,the high cost further limits its application in practice.In order to further reduce the cost of the catalyst,PdAgB/rGO catalyst is prepared without additives using graphene oxide as the support.The physical and chemical properties are characterized by XRD,TEM,XPS,ICP and FT-IR.It is found that B is doped into the PdAg alloy.The PdAgB nanoparticles are dispersed well on the support and the particle size is very small.At the same time,Ag,B and rGO all have some electrons transferred to the active metal Pd surface in the catalyst,making the Pd surface are rich in electrons.The introduction of Ag and B further reduces the cost of the catalyst,and the activity of the catalyst at room temperature reaches 164 h^-1,which is 12 times and 2 times that of Pd/rGO and PdAg/rGO catalysts,respectively.However,the catalyst performs not well in the stability test due to irreversible agglomeration of rGO during the reaction.In order to further improve the stability of the catalyst,the NH₂ functionalized titanium dioxide/graphene is used as support to prepare PdAg/NH₂-TNS-rGO catalyst.Its physicochemical properties are characterized by XRD,TEM,XPS,ICP,FT-IR and BET.It is found that the PdAg NPs is dispersed well on the support and the particle size is very small.The presence of NH₂ group makes the catalyst have excellent hydrophilic properties.At the same time,the active site Pd forms the electron-rich Pd active site due to the electronic effect of alloy and the metal-support interaction.The PdAg/NH₂-TNS-rGO catalytic formic acid dehydrogenation efficiency is as high as 1090 h^-1 at room temperature without any additives.At the same time,the catalyst performs well in the stability test because TNS has high stability under acidic conditions.