Challenges in the Design of Multi-Phase Multicomponent Alloys for Hydrogen Storage

Hydrogen is considered a low-carbon emission energy vector with the potential to replace fossil fuels in certain applications. However, the implementation of hydrogen as an energy carrier faces challenges, particularly in technological aspects such as the efficiency and safety of hydrogen storage. In this context, metal hydrides emerge as a promising option for hydrogen storage, offering high volumetric efficiency under moderate conditions of temperature and pressure. High entropy alloys, also generically known as multicomponent alloys, have drawn the attention of several research groups due to the increased number of systems and compositions that could be utilized as metal hydrides for hydrogen storage [1]. Several studies have reported the possibility of tailoring hydrogen storage performance through chemical compositional adjustments in systems that combine elements with both high and low affinity for hydrogen [1–3]. Most of these studies have focused on single-phase Body Centered Cubic (BCC) alloys and single-phase intermetallic compounds with the Laves C14 structure. However, a few recent studies suggest that multi-phase structures may offer advantages for the hydrogenation performance of multicomponent alloys, particularly in the activation and kinetics for hydrogen absorption [4,5]. In the present work, we will showcase new multi-phase multicomponent alloys designed for enhanced hydrogen storage behavior. The presence of refined morphological microstructural features will be discussed as potential contributors to improving the hydrogen storage properties of the studied alloys. Additionally, the benefits and challenges of using thermodynamic computational tools such as CALPHAD will be highlighted. Finally, we aim to provide a perspective for the next steps in the design of multi-phase multicomponent alloys for hydrogen storage applications, for example, how to define chemical compositions of the different phases to achieve compatible equilibrium pressures for hydrogen absorption/desorption and how to reach more sustainable compositions.<br/><br/>[1] M. Felderhoff, F. Marques, M. Balcerzak, F. Winkelmann, G. Zepon, Review and outlook on high-entropy alloys for hydrogen storage, Energy Environ Sci (2021). https://doi.org/10.1039/d1ee01543e.<br/>[2] B.H. Silva, W.J. Botta, G. Zepon, Design of a Ti–V–Nb–Cr alloy with room temperature hydrogen absorption/desorption reversibility, Int J Hydrogen Energy 48 (2023) 32813–32825. https://doi.org/10.1016/j.ijhydene.2023.05.032.<br/>[3] R.B. Strozi, B.H. Silva, D.R. Leiva, C. Zlotea, W.J. Botta, G. Zepon, Tuning the hydrogen storage properties of Ti-V-Nb-Cr alloys by controlling the Cr/(TiVNb) ratio, J Alloys Compd 932 (2023) 167609. https://doi.org/10.1016/j.jallcom.2022.167609.<br/>[4] S. Dangwal, K. Edalati, Significance of interphase boundaries on activation of high-entropy alloys for room-temperature hydrogen storage, Int J Hydrogen Energy 50 (2024) 626–636. https://doi.org/10.1016/j.ijhydene.2023.07.327.<br/>[5] B.H. Silva, W.J. Botta, G. Zepon, Achieving room temperature hydrogen storage reversibility in Nb-rich alloys of the Nb-Cr-Mn system, J Alloys Compd 1005 (2024). https://doi.org/10.1016/j.jallcom.2024.176187.