Superior Hydrogen Sorption Kinetics of Ti0.20Zr0.20Hf0.20Nb0.40 High-Entropy Alloy

Jianwei Zhang,Jian Zheng,Huahai Shen,Jingxia Yu,Jutao Hu,Sean Li,Haiyan Xiao,Xiaosong Zhou,Gang Huang,Pengcheng Li,Xia Xiang,Weiguang Zhang,Xiaotao Zu

doi:10.3390/met11030470

Abstract

High entropy alloys (HEAs) are composed of multiple main metal elements and have attracted wide attention in various fields. In this study, a novel Ti0.20Zr0.20Hf0.20Nb0.40 HEA was synthesized and its hydrogenation properties were studied, including sorption thermodynamics and hydrogen absorption/desorption kinetics. The maximum hydrogen absorption capacity was 1.5 H/atom at 573 K. X-ray diffraction (XRD) analysis indicated that the crystal structure of Ti0.20Zr0.20Hf0.20Nb0.40 HEA transformed from body-centered cubic (BCC) to body-centered tetragonal (BCT) with increasing hydrogen content, and to face-centered cubic (FCC) after hydrogen absorption to saturation. As a multi-principal element alloy, the Ti0.20Zr0.20Hf0.20Nb0.40 HEA possesses unique hydrogen absorption characteristics. The hydrogen absorption platform pressure rises gradually with the increase of the hydrogen absorption amount, which is caused by multiple kinds of BCT intermediate hydrides with consecutively increasing c/a. The full hydrogen absorption of the Ti0.20Zr0.20Hf0.20Nb0.40 HEA was completed in almost 50 s, which is faster than that of the reported hydrogen storage alloys in the literature. The experimental results demonstrate that the Ti0.20Zr0.20Hf0.20Nb0.40 HEA has excellent kinetic properties, unique thermodynamic hydrogen absorption performance, as well as a low plateau pressure at room temperature.

Highlights

With social and economic development, non-renewable energy sources, which have caused global environmental pollution, have become increasingly exhausted
The results suggested that Ti0.20 Zr0.20 Hf0.20 Nb0.40 High entropy alloys (HEAs) presents better thermal stability due to the higher binding energy of its hydride
The above values for the Ti0.20 Zr0.20 Hf0.20 Nb0.40 HEA were calculated to be δ = 5.51%, ∆Smix = 11.1 K·mol and ∆Hmix = 1.28 kJ/mol [38], which conforms to the principle of the formation of single phase HEA

Summary

Introduction

With social and economic development, non-renewable energy sources (such as coal, oil, etc.), which have caused global environmental pollution, have become increasingly exhausted. The premise of hydrogen energy application is based on the development of safe, economical and effective hydrogen storage materials [3,6]. There is a rich variety of solid hydrogen storage materials, including intermetallic compounds, complex hydrides and chemical hydrides, etc. Compared with gaseous hydrogen storage and liquid hydrogen storage, solid hydrogen storage demonstrates higher safety, higher hydrogen storage density and better reversibility [9,10,11]. Hydrogen storage alloys have been considered good hydrogen storage materials because of their high safety, low cost, non-greenhouse gas generation, high hydrogen storage per unit volume and high hydrogen absorption/release reversibility [12,13,14]. From metal to alloy to alloy doping, the composition of hydrogen storage alloys has becomes more and more complex with the development of research [8,14]

Methods

Results

Discussion

Conclusion