Preparation And Hydrogen Storage Properties Of UIO-66/Pt-GO Porous Composites

UIO-66,as a kind of metal-organic frameworks with high stability,has potential application prospects in the field of hydrogen storage due to its high porosity and large specific surface area.However,its hydrogen storage performance still does not meet the standards proposed by the US Department of Energy(DOE),especially the hydrogen storage capacity at room temperature is relatively low.To solve these problems,in this thesis,three composite materials were synthesized using UIO-66 as the matrix,and their structures and morphologies were characterized.The hydrogen storage properties of the three composite materials were discussed and studied.The results are as follows:(1)A series of UIO-66/GO composites were synthesized by solvothermal synthesis.For the first time,the effect of different content of GO additions on the low-temperature hydrogen storage capacity of UIO-66 was studied,and the mechanism of synergistic effect between formic acid,GO and UIO-66 was explored.Through the hydrogen storage experiments at 77 K and 0?40 bar,the results confirmed that the introduction of GO effectively improved the low-temperature hydrogen storage capacity of UIO-66.Among them,the UIO-66/GO-2 with a GO content of 2 wt% reached the highest hydrogen storage capacity of 3.08 wt%,which was higher than that of UIO-66,indicating a significant improvement.The hydrogen adsorption mechanism was discussed.UIO-66 and GO can effectively hybrid and new pores are generated,and formic acid coordinates with the carboxy groups contained in UIO-66 and the oxygen-containing groups on the surface of graphene oxide,while competing with it for competitive coordination,realize the induction of UIO-66 growth process and produce more crystal defects,thereby increasing the specific surface area and ultimately improving the hydrogen storage performance.(2)Pt-GO was synthesized by in situ reduction,and a series of UIO-66/Pt-GO composites were further synthesized for the first time.The effect of different amounts of Pt-GO on the hydrogen storage capacity of UIO-66 at room temperature was studied.The hydrogen storage experiment at 298 K and 0?40 bar shows that by successfully constructing the hydrogen spillover system,UIO-66/5%Pt-GO with 5 wt% Pt-GO shows the highest hydrogen storage performance,reaching hydrogen storage capacity of 0.58wt%.The hydrogen storage capacity of UIO-66 at room temperature increased by 232 %.The results show that it is feasible to improve the hydrogen storage capacity of UIO-66 at room temperature through the hydrogen spillover effect.(3)Pt-GO-MW with nanopores was synthesized by microwave in situ reduction method for the first time,and a series of UIO-66/Pt-GO-MW composites were further synthesized.The effects of different microwave times on the morphology of Pt-GO and the effects of doping on the hydrogen storage capacity of UIO-66 at room temperature were studied.The hydrogen storage experiment at 298 K and 0?40 bar shows that the best effect of hydrogen spillover can be achieved when the microwave time is 2 min,the corresponding hydrogen storage performance at room temperature is the highest,reaching0.66 wt %.The hydrogen adsorption mechanism was discussed.It was found that creating pores on the surface of GO can not only improve the kinetic performance of hydrogen adsorption,but also the unsaturated carbon at the edge of the hole can be used as an adsorption site,which can effectively improve the hydrogen spillover effect and thus increase the hydrogen storage capacity at room temperature.