Enhanced hydrogen storage properties of ZrTiVAl1- x Fe x high-entropy alloys by modifying the Fe content

Xiangfeng Ma; Xin Ding; Ruirun Chen; Xuefeng Gao; Yanqing Su; Hongzhi Cui

doi:10.1039/d2ra01064j

Enhanced hydrogen storage properties of ZrTiVAl_{1- x} Fe _x high-entropy alloys by modifying the Fe content

RSC Adv. 2022 Apr 11;12(18):11272-11281. doi: 10.1039/d2ra01064j. eCollection 2022 Apr 7.

Authors

Xiangfeng Ma¹, Xin Ding², Ruirun Chen¹, Xuefeng Gao², Yanqing Su², Hongzhi Cui¹

Affiliations

¹ School of Materials Science and Engineering, Shandong University of Science and Technology Qingdao 266500 PR China ruirunchen@hit.edu.cn +86-451-86412394 +86-451-86412394.
² National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology Harbin 150001 PR China dingxin_hit@hit.edu.cn.

Abstract

Lightweight ZrTiVAl high-entropy alloys have shown great potential as a hydrogen storage material due to their appreciable capacity, easy activation, and fast hydrogenation rates. In this study, transition metal Fe was used to improve the hydrogen storage properties of the equimolar ZrTiVAl alloy, and ZrTiVAl_1-x Fe _x (x = 0, 0.2, 0.4, 0.6, 0.8, 1) alloys were prepared to investigate the microstructure evolution and hydrogen storage properties. The results show that the ZrTiVAl_1-x Fe _x alloys are composed of a C14 Laves phase and Ti-rich HCP phase. With Fe substituting Al, the fraction of the C14 Laves phase increases and that of the HCP phase decreases. Besides, the interdendritic area fraction reaches the maximum when the Fe ratio is 0.2. The element V transferred to the C14 Laves phase from the HCP phase, which is caused by the strong affinity between V and Fe. The ZrTiVAl_1-x Fe _x alloys show enhanced hydrogenation kinetics and capacities. Notably, the ZrTiVFe alloy can reversely absorb 1.58 wt% hydrogen even at room temperature under 1 MPa H₂. The reduced interdendritic phase is beneficial to shorten the H atom diffusion distance, thus improving the hydrogenation rates. Both the transfer of the hydrogen-absorbing element V to the C14 Laves phase and the increased fraction of the C14 Laves phase lead to the increase of hydrogen storage capacity with the addition of Fe. Moreover, the increased Fe content leads to an increase of average valence electron concentration (VEC), where a larger VEC destabilizes the hydrides, and the desorption temperature of ZrTiVAl_1-x Fe _x hydride decreases significantly.