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Sensing mechanism of hydrogen storage on Li, Na and K‑decorated ­Ti2C Jiansheng Zhao1,4 · Wei Li1,2,3,4   · Ye Feng1,4 · Jinze Li1 · Gang Bai1,2 · Jie Xu1,2 Received: 21 August 2020 / Accepted: 2 November 2020 / Published online: 19 November 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract The adsorption of ­H2 molecules on Li, Na and K-decorated MXenes ­(Ti2C) has been investigated with first-principles calculations. A detailed examination of the adsorption mechanism of the Li, Na and K-decorated systems was presented by charge population analysis, electron density and partial density of states calculations. The results show that Li-decorated ­Ti2C system was found suitable for hydrogen storage. The maximum storage capacity about 4.33 wt% with a suitable average adsorption energy of − 0.26 eV/H2 can be obtained for two Li atoms, which adsorbed on both sides of the ­Ti2C. It indicates that Li-decorated ­Ti2C is of great significance for the wide application of MXenes in the field of hydrogen absorption. Keywords Ti2C · First principles · Electronic structure · Hydrogen storage

1 Introduction Developing high capacity, easy release and safety of hydrogen storage technology is crucial for hydrogen economy [1–4]. Due to its excellent chemical properties and unique morphology, MXene is widely used such as energy storage materials [5–9]. There are two mechanisms for this type of hydrogen storage. One is to induce the polarization of ­H2 molecules by increasing the electric field. And, the other is to hybridize ­H2 molecules by Kubas interaction [10–12]. In the polarization mechanism, metal atoms were adopted to modify two-dimensional materials to enhance the adsorption of ­H2 molecules. Many studies have proven the advantages of metal-decorated materials in hydrogen storage [13, 14]. Sheng et al. [15] reported that the co-doping of silicon through Li–Na was beneficial to the application * Wei Li [email protected] 1



College of Electronic and Optical Engineering and College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

2



National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210023, China

3

State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210093, China

4

Research Center of Optical Communications Engineering and Technology, Nanjing 210023, Jiangsu Province, China



in the field of hydrogen storage, and its average adsorption energy was ideal (0.29 eV/H2). Ataca et al. [16] studied the Li-doped graphene as a good hydrogen storage medium, which improved the interaction between graphene and ­H2, resulting in a large hydrogen storage capacity (12.8 wt%). Although the decoration of transition metals can increase the reserves through Kubas interaction, it is easy to polymerize on the surface of two-dimensional materials due to its high cohesive energy [17–19]. Due to the fiery heat of lithium batteries, a lot of research on Li adsorption by MXenes [20, 21] were studied. It has shown the feasib