Fe3O4@graphene as a superior catalyst for hydrogen de/absorption from/in MgH2/Mg. Issue 38 (14th September 2016)

• Record Type: Journal Article
• Authors: Bhatnagar, Ashish; Pandey, Sunita K.; Vishwakarma, Alok K.; Singh, Sweta; Shukla, Vivek; Soni, Pawan K.; Shaz, M. A.; Srivastava, O. N.
• Is Part Of: Journal of materials chemistry. Volume 4:Issue 38(2016)
• Page Start: 14761
• Page End: 14772
• Publication Date: 2016-09-14
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c6ta05998h
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : The present investigation describes the hydrogen sorption (de/absorption) behavior of MgH2 catalyzed by graphene sheet templated Fe3 O4 nanoparticles (Fe3 O4 @GS). Abstract : The present investigation describes the hydrogen sorption (de/absorption) behavior of MgH2 catalyzed by graphene sheet templated Fe3 O4 nanoparticles (Fe3 O4 @GS). Hydrogen sorption studies reveal that MgH2 catalyzed by Fe3 O4 @GS (MgH2 :Fe3 O4 @GS) offers improved hydrogen storage behavior as compared to stand-alone MgH2 catalyzed by graphene sheets (GS) (MgH2 :GS) or Fe3 O4 nanoparticles (MgH2 :Fe3 O4 ). The MgH2 :Fe3 O4 @GS has an onset desorption temperature of ∼262 °C (∼142 °C lower than pristine MgH2 ), while MgH2 :GS and MgH2 :Fe3 O4 have onset desorption temperatures of ∼275 °C and ∼298 °C respectively. In contrast to this, MgH2 :GS absorbs 4.40 wt% and MgH2 :Fe3 O4 absorbs 5.50 wt% in 2.50 minutes at 290 °C under 15 atm hydrogen pressure. On the other hand, MgH2 :Fe3 O4 @GS absorbs 6.20 wt% hydrogen in 2.50 minutes (which is considerably higher than recently studied catalyzed MgH2 systems) under identical temperature and pressure conditions. The MgH2 catalyzed with Fe3 O4 @GS shows negligible degradation of the storage capacity even after 25 cycles. Additionally, the desorption activation energy for MgH2 :Fe3 O4 @GS has been found to be 90.53 kJ mol −1 (which is considerably lower as compared to metal/metal oxide catalyzed MgH2 and fluorographene catalyzed MgH2 ). The formation enthalpy for MgH2 :Fe3 O4 @GS is 60.62 kJ per mole of H2 (13.44 kJ mol −1 lower than bulk MgH2 ). The catalytic effect of Fe3 O4 @GS has been described and discussed with the help of structural (X-ray diffraction (XRD)), micro structural (electron microscopy) and Raman spectroscopic studies.