Enhanced hydrogen generation behaviors and hydrolysis thermodynamics of as-cast Mg-Ni-Ce magnesium-rich alloys in simulate seawater

摘要

In this study, we developed as-cast (Mg10Ni)(1-x)Ce-x (x = 0, 5, 10, 15 wt%) ternary alloys by using a flux protection melting method and investigated their hydrolysis hydrogen generation behaviour in simulate seawater. The phase compositions and microstructures of as-cast (Mg10Ni)(1-x)Ce-x ternary alloys are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with electron energy dispersion spectrum (EDS) and transition electron microscope (TEM). Their kinetics, thermodynamics, rate-limiting steps and apparent activation energies are investigated by fitting the hydrogen generation curves at different temperatures. With increasing Ce content, the (Mg10Ni)(1-x)Ce-x ternary alloys show increased electrochemical activities and decreased eutectic. When 10 wt% and 15 wt% Ce added, the active intermediate phase of Mg12Ce has been observed. The hydrogen generation capacity of (Mg10Ni)(95)Ce-5 is as high as 887 mLg(-1) with a hydrolysis conversion yield of 92%, which is higher than that of MgloNi alloys (678 mLg(-1)) with a yield only 75% at 291 K. The initial hydrolysis reaction kinetics of Mg-Ni-Ce alloys is mainly controlled by the electrochemical activity and the mass transfer channels formed in the alloys. Such a structure-property relationship will provide a possible strategy to prepare Mg-based alloys with high hydrogen conversion yield and controlled hydrolysis kinetics/thermodynamics. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.