Ternary transition metal alloy FeCoNi nanoparticles on graphene as new catalyst for hydrogen sorption in MgH2

• Published in: International journal of hydrogen energy 2020-01, Vol.45 (1), p.774-786
• Main Authors: Singh, Sweta, Bhatnagar, Ashish, Shukla, Vivek, Vishwakarma, Alok K., Soni, Pawan K., Verma, Satish K., Shaz, M.A., Sinha, A.S.K., Srivastava, O.N.
• Format: Article
• Language: English
• Subjects: Graphene templated FeCoNi; Hydrogen storage; MgH2; Ternary alloy FeCoNi
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2019.10.204

The present investigation deals with the synthesis of ternary transition metal alloy nanoparticles of FeCoNi and graphene templated FeCoNi (FeCoNi@GS) by one-pot reflux method and there use as a catalyst for hydrogen sorption in MgH2. It has been found that the MgH2 catalyzed by FeCoNi@GS (MgH2: FeCoNi@GS) has the onset desorption temperature of ~255 °C which is 25 °C and 100 °C lower than MgH2 catalyzed by FeCoNi (MgH2: FeCoNi) (onset desorption temperature 280 °C) and the ball-milled (B.M) MgH2 (onset desorption temperature 355 °C) respectively. Also MgH2: FeCoNi@GS shows enhanced kinetics by absorbing 6.01 wt% within just 1.65 min at 290 °C under 15 atm of hydrogen pressure. This is much-improved sorption as compared to MgH2: FeCoNi and B.M MgH2 for which hydrogen absorption is 4.41 wt% and 1.45 wt% respectively, under the similar condition of temperature, pressure and time. More importantly, the formation enthalpy of MgH2: FeCoNi@GS is 58.86 kJ/mol which is 19.26 kJ/mol lower than B.M: MgH2 (78.12 kJ/mol). Excellent cyclic stability has also been found for MgH2: FeCoNi@GS even up to 24 cycles where it shows only negligible change from 6.26 wt% to 6.24 wt%. A feasible catalytic mechanism of FeCoNi@GS on MgH2 has been put forward based on X-ray diffraction (XRD), Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Photoelectron Spectroscopy (XPS), and microstructural (electron microscopic) studies. Synthesis of ternary FeCoNi@GS alloy by one pot method and its application as catalyst for improving de/rehydrogenation properties of MgH2. [Display omitted] •Synthesis of FeCoNi@GS by one pot method.•FeCoNi@GS has been used as catalyst for MgH2.•MgH2 catalyzed by FeCoNi@GS show excellent cyclability.•Formation enthalpy of MgH2: FeCoNi@GS is reduced by 19.26 kJ/mol of H2 as compared to ball milled MgH2.