Preparation Of Palladium-based Catalyst For Hydrogen Production From Formic Acid And Study Of Its Influencing Factor

While hydrogen is often regarded as a clean fuel,one of the barriers causing the growth of the"hydrogen economy"is how to adequately safeguard and release hydrogen.Traditional hydrogen storage technology is costly to transport,risky,and demands plenty of energy.Due to its huge hydrogen storage capacity,cheap cost,and excellent safety,liquid organic hydrogen carriers（LOHC）is attracting a lot of notice.Formic acid（HCOOH）is regarded as a superior liquid hydrogen storage substance due to its high hydrogen concentration,low price,safe transportation,and capability to produce hydrogen in low-temperature conditions.The development of efficient and safe supported palladium-based catalysts for formic acid hydrogen production is a current research hotspot.For enhancing catalytic activity,multiple methods like creating supports and doping multi-element metals have been used.The primary approach for enhancing the catalyst’s catalytic activity is to modify the interaction between the support and the metal.Based on this,the project initially constructed a catalyst selecting Ce O₂ as the carrier,investigated the link between the structure and activity of the metal and the carrier,as well as the reaction mechanism,before using activated carbon as the carrier to investigate the variables in the catalyst creation process.the effects of formic acid’s ability to produce hydrogen.The following is a summary of the full research’s findings:（1）The hydrothermal method was utilized for making cerium oxide nanorods（Ce O₂-r）,octahedrons（Ce O₂-o）,cubes（Ce O₂-c）,and truncated cubes（Ce O₂-tc）.To generate a supported Pd/Ce O₂ catalytic agent,Pd was then loaded onto Ce O₂-c using the liquid phase reduction technique.Pd/Ce O₂-tc was the best catalytic activity for hydrogen production from the disintegration of formic acid among the four Pd/Ce O₂catalysts mentioned above.Pd/Ce O₂-tc has a TOF of 1270 h^-1 at 303 K,which is 4.5,5.1,and 2.7 times more than Pd/Ce O₂-c,Ce O₂-o,and Ce O₂-r.The apparent activation energy of Pd/Ce O₂-tc catalyzed formic acid decomposition for hydrogen production is only 28.8 k J/mol.Through XPS,Raman,and H₂-TPR analysis,it has been shown that the strong metal’s interaction with the carrier between Pd NPs and Ce O₂-tc,which lowers the electron cloud density of Pd species on the surface,is the cause of the high catalytic activity of Pd/Ce O₂-tc.Additionally,it exhibits a high species concentration of Pd₀-O_V-Ce³⁺and a high surface oxygen vacancy（O_V）ratio.In situ infrared results showed that the interaction between the strong metal and the carrier in Pd/CeO₂-tc increased the generation of key intermediate species bidentate formic acid complexes HCOO*into （HCOOH-HCOO*）from HCOOH and accelerated the decomposition of HCOOH--HCOO*,CO₂,and H₂.（2）The main focus of the research was on the effects of carrier treatment process,Pd²⁺ligand structure,and Na BH₄ reduction conditions on the effectiveness of Pd/C catalytic formic acid hydrogen production.A series of Pd/C catalysts were prepared by loading Pd on the carrier activated carbon XC-72 by impregnation reduction method.The findings demonstrate that pretreatment of the activated carbon carrier may substantially boost its capacity to anchor Pd NPs,and that amino acids with a basic isoelectric point can improve the carrier’s capacity to complex the Pd NPs.The findings also show that the Pd/C-L-Arg with the highest TOF is 1178 h^-1.The catalytic activity of Pd²⁺is significantly influenced by its ligand structure.The most effective ligand for Pd Cl₂ as a metal precursor is the halogen salt Na Cl,which has a better effect than Na Br and Na I.The reduction TOF at 0°C is as high as 1518 h^-1.When Na BH₄ is utilized,the catalyst’s performance declines as the reduction temperature rises.Low-temperature reduction conditions function well.To increase catalytic activity,low-temperature use can successfully slow down sodium borohydride’s rate of reduction and reduce the average particle size of Pd NPs.