Chitosan Immobilized Pd Nanoparticles For Enhanced Catalytic Dehydrogenation Of Formic Acid

Hydrogen（H₂）has a positive effect on solving energy depletion and environmental pollution problems.However,there are technical difficulties and potential safety hazards in the storage and transportation of hydrogen.The catalytic hydrogen production from liquid hydrogen storage material is a good solution to this problem,formic acid（HCOOH）with the theoretical hydrogen content is 4.4 wt%and has drawn intense interest in recent years.Despite the Pd-based catalysts have received increasing attention as the most promising catalysts for the dehydrogenation from formic acid,the Pd NPs immobilized on support still remains a challenge.In this paper,the natural organic material chitosan is used as support to immobilize Pd NPs and obtained the Pd/chitosan catalyst,which exhibit high efficiency and stable hydrogen production via catalytic formic acid at room temperature.The research content is divided into the following two parts:（1）Porous chitosan microspheres with large specific surface area were prepared by emulsion polymerization using chitosan as raw material synthesize,whose acid resistance property was further improved by cross-linking using glutaraldehyde.The abundant amino and carboxyl groups on the surface of the microspheres are beneficial to stabilize nano-Pd,enabling it to achieve high efficiency and stable hydrogen production via catalytic formic acid at room temperature.The XPS analysis proved that the electronic interaction between the metal Pd and the N atoms on the chitosan surface could increase the electron cloud density on the N atoms.The accumulated electrons subsequently transfer to H⁺,resulting in the production of hydrogen.The turn-over frequency is 67.3 h^-1,which is 1.7 times higher that of the traditional Pd/C catalyst under the same conditions.（2）The chitosan fiber is prepared by electrospinning technology.Compared with the chitosan microspheres prepared by polymerization,the chitosan fibers have stronger mechanical properties.The activity of Pd/chitosan fiber catalyst remained unchanged after 20 cycles（60 h）.The effects of sodium formate（SF）and ammonium formate（AF）on the catalytic hydrogen production reaction were also investigated.The TOF of the Pd/chitosan fiber catalyst in the FA-SF and FA-AF mixed system to catalyze hydrogen production at room temperature is 307.5h^-1and 1757.2 h^-1,respectively.Among them,the addition of SF could increase the concentration of intermediate HCOO^-and accelerate the Pd²⁺→Pd⁰transition,and the addition of AF could create more active sites of Pd-N while increasing the concentration of HCOO^-.In summary,this study catalyzes hydrogen from formic acid through the synergy effect of organic matter and metal nanoparticles,breaking through the traditional inorganic supporter loading method,and provides a new direction for nano-metal-loaded catalyst.