Effect of graphene templated fluorides of Ce and La on the de/rehydrogenation behavior of MgH2. (3rd August 2017)

• Record Type: Journal Article
• Authors: Soni, Pawan K.; Bhatnagar, Ashish; Shaz, M.A.; Srivastava, O.N.
• Is Part Of: International journal of hydrogen energy. Volume 42:Number 31(2017)
• Page Start: 20026
• Page End: 20035
• Publication Date: 2017-08-03
• Subjects: Hydrogen storage -- MgH2 -- Graphene templating -- Rare earth metal fluorides; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2017.05.233
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: The present investigation describes the hydrogen storage properties of MgH2 ball milled with different additives i.e. graphene templated rare earth metal (La and Ce) fluorides, CeF4 and LaF3 . MgH2 ball milled with graphene templated CeF4 (MgH2 :CeF4 @Gr) has onset desorption temperature of 245 °C, which is 50 °C, 52 °C and 75 °C lower than MgH2 ball milled with LaF3 templated graphene, CeF4 and LaF3 respectively. CeF4 @Gr also shows the superior effect amongst all additives during rehydrogenation where MgH2 :CeF4 @Gr absorbs 5.50 wt% within 2.50 min at 300 °C under 15 atm H2 pressure. Dual tuning effect, i.e. lowering of thermodynamic (62.77 kJ/mol H2 : lower from 74 kJ/mol for pristine MgH2 ) and kinetics barrier (93.01 kJ/mol) has been observed for MgH2 :CeF4 @Gr. Additionally, MgH2 ball milled with CeF4 @Gr shows good reversibility up to 24 cycles of de/rehydrogenation. The feasible working mechanism of CeF4 @Gr as additive for MgH2 has been studied in detail with the help of Transmission Electron Microscope (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction characterizations (XRD). Graphical abstract: The present study suggest that in contrast to stand alone additive (ie. CeF4 and LaF3 ), Gr templated additive (i.e. CeF4 @Gr and LaF3 @Gr) shows improved hydrogen sorption in MgH2 . Lower desorption temperature (245 °C) and dual tuning effect, i.e. lowering of thermodynamic (62.77 kJ/mol H2 : lower from 74 kJ/mol for pristine MgH2 ) and kinetics barrier (93.01 kJ/mol) has been observed for MgH2 ball milled with CeF4 @Gr (MgH2 :CeF4 @Gr). Additionally, MgH2 :CeF4 @Gr shows good reversibility up to 24 cycles of de/rehydrogenation. The feasible working mechanism of CeF4 @Gr as additive for MgH2 has been studied in detail with the help of Transmission Electron Microscope (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction characterizations (XRD). Highlights: Gr templated additive shows better catalytic effect than stand alone additive. Lowering of thermodynamic and kinetics barrier has been observed for MgH2 :CeF4 @Gr. MgH2 ball milled with CeF4 @Gr shows good cyclic stability. Synergistic effect of CeH2 and MgF2 improves the sorption property of MgH2 :CeF4 @Gr. Gr as template avoids the agglomeration and increases the stability of catalyst.