Abstract
The single-phase multi-principal-component CoFeMnTiVZr alloy was obtained by rapid solidification and examined by a combination of electrochemical methods and gas–solid reactions. X-ray diffraction and high-resolution transmission electron microscopy analyses reveal a hexagonal Laves-phase structure (type C14). Cyclic voltammetry and electrochemical impedance spectroscopy investigations in the hydrogen absorption/desorption region give insight into the absorption/desorption kinetics and the change in the desorption charge in terms of the applied potential. The thickness of the hydrogen absorption layer obtained by the electrochemical reaction is estimated by high-resolution transmission electron microscopy. The electrochemical hydrogen storage capacity for a given applied voltage is calculated from a series of chronoamperometry and cyclic voltammetry measurements. The selected alloy exhibits good stability for reversible hydrogen absorption and demonstrates a maximum hydrogen capacity of ∼1.9 wt% at room temperature. The amount of hydrogen absorbed in the gas–solid reaction reaches 1.7 wt% at 298 K and 5 MPa, evidencing a good correlation with the electrochemical results.
Highlights
The gas–solid reaction method or pressure-composition isotherm (PCI) measurements are widely used for the estimation of the reversible hydrogen storage capacity in different metallic alloys and intermetallic compounds.[18]
The preparation of the single-phase equiatomic multi-principal-component alloys (MPCs) CoFeMnTiVZr alloy with homogeneous grain structure is a complicated procedure in conventional arc-melting which results in texture orientation or formation of large grains
The X-ray diffractometer (XRD) analysis of the as-cast alloy indicates the formation of a hexagonal Laves phase structure (C14 type) characteristic of intermetallic compounds formed by metals with a large difference in atomic radii as in the case of the ZrTiVNiCrFe MPC alloy.[51]
Summary
The gas–solid reaction method or pressure-composition isotherm (PCI) measurements are widely used for the estimation of the reversible hydrogen storage capacity in different metallic alloys and intermetallic compounds.[18]. Paper estimate of the hydrogen capacity is inaccurate for MPC alloys with different types of crystalline structures In such systems, the estimation of hydrogen storage by electrochemical reactions is more reasonable.[28,29,30]. Hydrogen absorption and evolution reactions have attracted growing interest in the past years due to their insufficient kinetics, i.e. low conductivity of OHÀ ions in alkaline electrolytes.[50] This slow kinetics may challenge the development of anionic exchange membrane water electrolyzers For this reason, multi-component alloy systems can be envisioned to allow tuning of the ion transfer in the electrolytes and, to enhance the absorption and electrocatalytic behavior. The overall study of the methodology used in the present work is interesting for assessing the applicability of electrochemical and physical methods for the evaluation of the hydrogen storage and release performance of novel materials
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