Exploring Hydrogen Incorporation into the Nb4AlC3 MAX Phases: Ab Initio Calculations

Yudong Fu; Zifeng Li; Weihong Gao; Danni Zhao; Zhihao Huang; Bin Sun; Mufu Yan; Guotan Liu; Zihang Liu

doi:10.3390/ma15217576

Exploring Hydrogen Incorporation into the Nb₄AlC₃ MAX Phases: Ab Initio Calculations

Materials (Basel). 2022 Oct 28;15(21):7576. doi: 10.3390/ma15217576.

Authors

Yudong Fu¹, Zifeng Li¹, Weihong Gao¹, Danni Zhao¹, Zhihao Huang², Bin Sun¹, Mufu Yan³, Guotan Liu¹, Zihang Liu⁴

Affiliations

¹ College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China.
² Department of Materials Science and Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong SAR, China.
³ School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China.
⁴ State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China.

Abstract

The Nb₄AlC₃ MAX phase can be regarded as a TMC structure with stacking faults, which has great potential as a novel solid hydrogen storage material. Herein, we used ab initio calculations for understanding the hydrogen incorporation into Nb₄AlC₃ MAX phases, including equilibrium structural characteristics, energy changes, electronic structures, bonding characteristics, and diffusion paths. According to the calculated results, H has thermal stability in the interstice of the Nb-Al layer, and the most probable insertion site is an octahedron (3-site) composed of three Nb atoms and three Al atoms. When C vacancies are introduced, the Nb-C layer has a specific storage capacity for H. In addition, Al vacancies can also be used as possible sites for H incorporation. Moreover, the introduction of vacancies significantly increase the hydrogen storage capacity of the MAX phase. According to the electronic structure and bonding characteristics, the excellent hydrogen storage ability of the Nb₄AlC₃ structure may be due to the formation of ionic bonds between H and Nb/Al. It is worth noting that the H-Al bond in the 1-site is a covalent bond and an ionic bond key mixture. The linear synchronous transit optimization study shows that only H diffusion in Al vacancies is not feasible. In conclusion, the Nb-Al layer in Nb₄AlC₃ can provide favorable conditions for the continuous insertion and subsequent extraction of H, while the vacancy structure is more suitable for H storage. Our work provides solid theoretical results for understanding the hydrogen incorporation into Nb₄AlC₃ MAX phases that can be helpful for the design of advanced hydrogen storage materials.

Keywords: Nb4AlC3 MAX phase; ab initio calculations; diffusion mechanism; hydrogen storage.

Grants and funding

This project was supported by Heilongjiang Province “Hundreds and Tens of Thousands” Major Projects of Engineering Science and Technology (2019ZX10A01), Natural Science Foundation of Heilongjiang Province (LH2021E029), the National Key R&D Program (2018YFB2001904), microstructure control and properties of laser composite ion nitriding modified layer (19QB1402300), development and application performance evaluation of deformation heat treatment technology for high-strength and high-toughness 2624 aluminum alloy sheet, Central University Fund (3072021CFT1009).