Synergetic effect of C and Ni on hydrogen release from Mg-Ni-electrochemically synthesized reduced graphene oxide based hydride

• Published in: Sustainable energy & fuels 2021-09, Vol.5 (17), p.4414-4424
• Main Authors: Panda, Srikanta, Satya Aditya, Marla V. V, Tatiparti, Sankara Sarma V
• Format: Article
• Language: English
• Subjects: Ball milling; Catalysts; Doppler effect; Electron transfer; Graphene; Hydrogenation; Nanocomposites; Nickel; Photoelectron spectroscopy; Photoelectrons; Red shift; Room temperature; Synthesis; Unit cell; X ray photoelectron spectroscopy; X-ray diffraction
• ISSN: 2398-4902; 2398-4902
• DOI: 10.1039/d1se00842k

Mg-reduced graphene oxide (rGO), Mg-Ni and Mg-Ni-rGO nanocomposites were synthesized by ball milling. They were subsequently hydrogenated at P H2 15 bar, ∼320 °C. Isothermal (∼320 °C) and non-isothermal (room temperature - 450 °C, 5 °C min −1 ) H release experiments were performed on the hydrogenated nanocomposites. The incubation time (dH/d t | 320°C 0) during isothermal H release drops from ∼15 min in Mg-rGO to ∼75 s in Mg-Ni and ∼60 s in Mg-Ni-rGO. The onset temperature during non-isothermal H release reduces from ∼350 °C in Mg-rGO to ∼275 °C in Mg-Ni-rGO. The reasons for the superior H release by Mg-Ni-rGO are investigated. Ball milling of Mg-rGO develops persistent Mg-C interaction at ∼283 eV from C1s X-ray photoelectron spectroscopy (XPS), involving electron transfer between Mg and C. In Mg-Ni, a non-stoichiometric Mg 2 NiH x phase and MgH 2 unit cell shrinkage develop upon H uptake resulting in improved H release. Mg-Ni-rGO possesses unreacted metallic Ni (X-ray diffraction) upon ball milling; Ni-C interaction (∼283.5-284.5 eV, C1s XPS) and red shift in G band (Raman) vis-à-vis Mg-rGO upon H uptake. Interestingly, Mg-Ni-rGO exhibits the individual effects of rGO and Ni addition. The Ni-C interaction from metallic Ni and possibly from Mg 2 NiH x lead to the superior H release by Mg-Ni-rGO. This work demonstrates the synergetic effect of adding multiple catalysts on H release. Schematic representation of synergetic effect aiding in superior hydrogen release from Mg-Ni-rGO nanocomposite.