Preparation And Characterization Of Two Dimensional Mxene Supported Catalysts Study On Catalytic Performance Of Hydrogen Production

The massive burning and consumption of fossil energy has brought about a lot of environmental problems,and failing to meet people’s vision of long-term development in the future.Therefore,the hydrogen economy with hydrogen as the medium is put forward.Hydrogen is a kind of clean and renewable energy,which is widely distributed in nature.Hydrogen is not stable in some cases and circumstances,which has some problems of safety and application cost.Since chemical hydrogen storage was put forward as a solution,it has attracted much attention.Hydrogen storage carriers commonly used in chemical hydrogen storage mainly include formic acid,hydrazine hydrate,aminoborane and so on.Chemical hydrogen storage carriers can decompose hydrogen completely at relatively low temperature（298 K-333 K）under catalytic action,so as to solve the safety and efficiency problems of hydrogen energy in practical application process,which is one of the necessary means for large-scale application of hydrogen energy.In this paper,the dehydrogenation properties of MXene supported metal nanoparticles catalysts for formic acid and hydrazine hydrate were studied.On this basis,the effects of MXene modification and metal nanoparticles alloying on the catalytic activity of formic acid were further investigated.A series of supported metal nanoparticles catalysts were designed and prepared for dehydrogenation of formic acid.The main research contents are as follows:（1）A variety of MXene materials were prepared by in-situ hydrofluoric acid etching precursor system,and bimetallic alloy metal nanoparticles supported by these MXene materials were used to construct catalysts,and their catalytic performance in the dehydrogenation of hydrazine hydrate was further tested.The catalysts prepared with V₂C as support showed considerable catalytic activity and selectivity.TEM characterization showed that PtNi nanoparticles with uniform size of about 2 nm were formed on the surface of V₂C.Pt_0.3Ni_0.7/V₂C prepared by a series of composition comparison optimization shows good catalytic activity of hydrazine hydrate dehydrogenation at 323K,TOF is 800 h^-1,H₂ selectivity is close to 100%.（2）A simple wet chemical method was used to prepare two-dimensional transition metal carbides（MXene）;PDA-MXene was prepared by alkalization of p-phenylenediamine（PDA）on MXene.And further,Pd metal nanoparticles（NPs）were conveniently loaded on the surface to catalyze the dehydrogenation of formic acid.The as-prepared Pd/PDA-MXene catalyst for the formic acid dehydrogenation was characterized by XRD,IR,TEM,and XPS.Pd NPs with a size of about 4 nm were formed upon the PDA-MXene support surface and were well dispersed.The Pd/PDA-MXene exhibited good catalytic activity in the formic acid decomposition process without any additives,and the turnover frequency value at 50°C was 924.4h^–1.It is worth mentioning that the prepared catalyst maintained good catalytic activity in five consecutive catalytic cycles of the formic acid dehydrogenation experiment.（3）Heterogeneous catalysis of formic acid dehydrogenation is considered as a promising strategy for safe and efficient hydrogen production and transportation.Herein,we reported the immobilization of the bimetallic PdCr nanoparticles on amine-functionalized titanium carbides（PdCr/NH₂-MXene）.By the amine group,the ultrafine PdCr NPs with the size of 1.8 nm were well dispersed on MXene.The optimized Pd_0.7Cr_0.3/NH₂-MXene system exhibit an excellent activity toward catalyzing FA dehydrogenation,affording the overall turnover frequency（TOF）value of as high as 1906 h^-1 at 323 K.This work may supply a new strategy for development of high-performance bimetallic nanosystem for tremendous catalytic application in the future.