Preparation Of Metal-organic Frameworks/Graphene Derivatives For Hydrogen Storage Performance

In recent years,many energy and environment problems were caused by the increasing use of fossil fuels.Hydrogen is a potential substitute for traditional fossil fuels because of its renewable,pollution-free and high calorific value.However,hydrogen storage is always the key technical problem for the large-scale application of hydrogen energy.Hydrogen storage by physisorption has attracted growing attention due to its adsorption/release reversibility and easy operation.Metal-organic frameworks(MOFs)have been widely investigated for gas separation,storage and catalysis for its high porosity,ultrahigh surface area and structural diversity,which is also the most potential adsorbents for hydrogen storage.However,the hydrogen storage capacity of most MOFs is not satisfactory.Recently,incorporating MOFs into Graphene derivatives is able to increase their gas adsorption capacity.Combining MOFs with graphene oxide(GO)or graphene aerogel(GA)have been winning increasing attentions due to their synergistic effect on gas adsorption performance.In order to explore the H₂ storage performance of composites,MOFs/GO and MOFs/GA for hydrogen storage were prepared and investigated in this work.Ui O-66/GO composites with different contents of GO were synthesized by hydrothermal synthesis,and then characterized by Powder X-ray Diffraction(PXRD),Scanning Electron Microscopy(SEM),Thermogravimetric Analysis(TGA)and specific surface area analysis(BET).The effect of different contents of GO on the Ui O-66 crystal structure and hydrogen storage capacity were revealed.The results demonstrated that the addition of appropriate GO can improve the specific surface area and micropore volume of the composite,thus leading to increased hydrogen storage capacity.The specific surface area and the micropore volume of Ui O-66/GO-10%with 10 wt%GO is the largest,and thus the hydrogen storage of Ui O-66/GO-10%is the highest(2.39 wt%),which is 17%higher than pure Ui O-66.Such phenomena suggested that the addition of GO can improve the hydrogen storage performance of MOFs.Considering the synthesis condition and operation complexity of adsorbents,we prepared a HKUST-1/GA composite in bulk form under mild synthesis condition and measured the H₂adsorption isotherms.Grand Canonical Monte Carlo(GCMC)molecular simulation was also carried out to reveal the hydrogen adsorption mechanism.The experimental results show that the hydrogen storage capacity of the HKUST-1/GA composite is 2.14 wt%at 77 K,100bar,which is 42%higher than that of HKUST-1,similar to the tendency observed in GCMC simulations.Moreover,GCMC simulation also revealed that that the adsorbed hydrogen molecules were mostly assembled in the interface of HKUST-1/GA composite,suggesting the interface of HKUST-1 and GA can effectively improve the hydrogen storage capacity of composite.