Enhanced electrochemical and hydrogen storage properties of La-Mg-Ni-based alloy electrode using a Ni and N co-doped reduced graphene oxide nanocomposite as a catalyst

To enhance the electrochemical property of a La0.7Mg0.3(Ni0.9Co0.1)(3.5) alloy, a three-dimensional (3D) reduced graphene oxide (rGO)-supported nickel and nitrogen co-doped (Ni-N@rGO) nanocomposite is fabricated by an impregnation method and introduced into the La0.7Mg0.3(Ni0.9Co0.1)(3.5) alloy. The results show that the reversible hydrogen storage property and the comprehensive electrochemical performance of the La0.7Mg0.3(Ni0.9Co0.1)(3.5) alloy are enhanced effectively when it is modified by the Ni-N@rGO nanocomposite. The high-rate dischargeability values at a discharge current density of 1500 mA g(-1) for the La0.7Mg0.3(Ni0.9Co0.1)(3.5) alloy and Ni-N@rGO-modified samples are 0.0% and 70.5%, respectively. Additionally, the anodic peak currents for the unmodified alloy electrode is 892 mA g(-1). Under the catalytic action of the Ni-N@rGO nanocomposite, the value increases to 2307 mA g(-1), which is 2.59 times larger than that of unmodified samples. The results also indicate that the diffusion ability of the hydrogen atom in the alloy electrode body enhances significantly when modified by the Ni-N@rGO nanocomposite. The hydrogen diffusion coefficient for the La0.7Mg0.3(Ni0.9Co0.1)(3.5) alloy electrode increases from 3.93 x 10(-10) cm(2) s(-1) to 6.15 x 10(-10) cm(2) s(-1) when is modified by Ni-N@rGO nanocomposite. These improvements in the comprehensive electrochemical properties are mainly attributed to the excellent electrochemical activity and conductivity of the Ni-N@rGO nanocomposite. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.