Modeling of the hydrogen sorption kinetics in an AB2 laves type metal hydride alloy

Arif Hariyadi,Suwarno Suwarno,Roman V Denys,Jose Bellosta Von Colbe,Tor Oskar Sætre,Volodymyr Yartys

doi:10.1016/j.jallcom.2021.162135

Abstract

Hydrides of the AB2 Laves type alloys (A=Zr, Ti; B = transition metal – Fe, Co, Ni, Mn, Cr, V) have been extensively studied as materials for the storage of gaseous hydrogen. They contain up to 4 H atoms/formula unit AB2, thus achieving reversible H storage capacities in the range between 1.5 and 2.0 wt% H and offering high rates of hydrogen charge and discharge, thus making them suitable for designing efficient hydrogen stores operating at ambient conditions. In the present study, we performed an experimental study and modeling of the thermodynamics and the kinetics of interaction in the AB2-hydrogen system. The experimental data was collected by studying a model alloy with a composition Ti0.15Zr0.85La0.03Ni1.126Mn0.657V0.113Fe0.113. Hydrogen absorption and desorption were studied in a volumetric Sieverts type apparatus at isothermal conditions using a single-step change/discharge and stepwise methods. The results obtained from the model simulation show that the reaction follows the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, with the value of exponent n = 1–1.25 for absorption and 1 for desorption. This indicates that the rate-limiting hydrogen absorption and desorption steps are jointly governed by hydrogen diffusion and grain boundary nucleation of alpha-solid solution and beta-hydride. The activation energies for both hydrogen absorption and desorption decrease along with increasing hydrogen content in the hydride.

Highlights

The need for energy storage is increasing because of the ex tensive development of renewable energy technologies
A challenge for the various metal hydride-based hydrogen storage applications integrated with fuel cells is in developing H storage systems with good kinetics
The experiments were conducted using a single-step absorption and desorption and stepwise methods. Both hydrogen absorption and desorption proceed faster with increasing tempera ture as indicated by the increase of the temperature rate term K(T), except when the thermodynamics influences the rates of the ab sorption process at pressures close to the equilibrium conditions

Summary

Introduction

The need for energy storage is increasing because of the ex tensive development of renewable energy technologies. Batteries are considered ideal energy storage devices, but in the case of long-term or seasonal energy storage, batteries have limita tions caused by the energy loss due to a self-discharge, further to a high cost of the battery system together with a limited energy sto rage capacity. These limitations can be overcome by using hydrogen. Hydrogen is considered as an energy carrier obtained utilizing excess seasonal photovoltaic or wind power. A challenge for the various metal hydride-based hydrogen storage applications integrated with fuel cells is in developing H storage systems with good kinetics. A hydrogen storage tank is expected to provide a spe cific flow rate of hydrogen supply sufficient for a normal operation of a fuel cell [6]

Methods

Results

Conclusion