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

Mg-reduced graphene oxide (rGO), Mg-Ni and Mg-Ni-rGO nanocomposites were synthesized by ball milling. They were subsequently hydrogenated at P-H2 approximate to 15 bar, similar to 320 degrees C. Isothermal (similar to 320 degrees C) and non-isothermal (room temperature - 450 degrees C, 5 degrees C min(-1)) H release experiments were performed on the hydrogenated nanocomposites. The incubation time (dH/dt|(320 degrees C) approximate to 0) during isothermal H release drops from similar to 15 min in Mg-rGO to similar to 75 s in Mg-Ni and similar to 60 s in Mg-Ni-rGO. The onset temperature during non-isothermal H release reduces from similar to 350 degrees C in Mg-rGO to similar to 275 degrees 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 similar to 283 eV from C1s X-ray photoelectron spectroscopy (XPS), involving electron transfer between Mg and C. In Mg-Ni, a non-stoichiometric Mg2NiHx phase and MgH2 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 (similar to 283.5-284.5 eV, C1s XPS) and red shift in G band (Raman) vis-a-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 Mg2NiHx lead to the superior H release by Mg-Ni-rGO. This work demonstrates the synergetic effect of adding multiple catalysts on H release.

Automated summary

In this study, Mg-reduced graphene oxide (rGO), Mg-Ni, and Mg-Ni-rGO nanocomposites were synthesized by ball milling and subsequently hydrogenated for H release experiments. Mg-Ni-rGO demonstrated the unique effects of graphene and nickel addition, with Ni-C interaction and non-stoichiometric Mg2NiHx phase contributing to superior H release. This work highlights the synergetic effect of multiple catalysts on hydrogen release.