Absorption and diffusion kinetics of hydrogen in Y₅Si₃, one-dimensional electride

Electrides are ionic compounds in which “free” electrons are confined in a low-dimensional cavity to balance the charge states of the system. The characteristic features of electrides—the existence of large cavities and non–nucleus-bound electrons—make them attractive for various applications, such as gas storage, electron/ion transport, and electrocatalytic processes. The compound Y₅Si₃ is a 1D electride with excellent catalytic efficiency. In addition, recent studies indicate its reversible hydrogen storage capability. However, the detailed atomistic understanding is far from being complete. Using first-principles density functional theory in combination with global structure search algorithms, we investigate the absorption and diffusion kinetics of hydrogen in the Y₅Si₃ compound. We identify the 1D cavity as the dominant diffusion channel, where the diffusion process is strongly influenced by the density of hydrogen. Therefore, the fastest kinetics can be achieved at a certain density of hydrogen. Our results provide a better understanding of gas absorption in 1D electrides, and in general their application as efficient ion-transport medium.