First-principle prediction of one-dimensional silicon allotropes: Promising new candidate for chemical and electrochemical hydrogen storage

Silicon is an excellent candidate for efficient hydrogen-storage medium, but hydrogen is mainly stored on the surface of silicon structure and the large volume expansion and contraction of structure during hydrogen storage/release seriously damages its structural stability. In order to increase hydrogen concentration values in silicon nanostructures and enhance the cyclic stability of structure, we predicted 1D silicon allotropes at different ambient hydrogen concentration conditions, and investigated the structural stability and electronic properties of these allotropes. The results show that the spaces around these structures give them a larger degree of freedom and the H2 filled in the interspaces also continuously provides them with sufficient hydrogen sources for supplement and replacement. Most of the generated 1D silicon allotropes are both dynamically and thermodynamically stable and most of them are semiconductors. The low structural dimension ensures that these 1D silicon allotropes have high chemical hydrogen storage capacity, and the structural stability at ambient hydrogen concentration provides a strong guarantee for the cyclic stability of chemical and electrochemical hydrogen storage for these allotropes. Moreover, hydrogen atoms can diffuse not only on the surface of 1D silicon allotropes but also between two closely spaced 1D silicon allotropes, which provides more convenience for the application of 1D silicon allotropes in chemical and electrochemical hydrogen storage. Our results can enrich the library of 1D silicon nanostructures used for hydrogen storage and provide more understanding of their structural stability and electronic properties, which can provide theoretical reference for their future application.