High-Capacity Reversible Hydrogen Storage on Calcium-Decorated Silicene: A DFT Study.

First-principles DFT calculations have been employed to examine the hydrogen storage behavior of Ca-decorated silicene. A single Ca atom binds to the hollow site of the silicene monolayer with a binding energy of -2.348 eV, the magnitude of which exceeds the cohesive energy of bulk Ca, thus preventing Ca clustering. Pristine silicene interacts weakly with H2, with an adsorption energy of only -0.047 eV, while Ca decoration notably enhances the binding affinity to -0.561 eV. Each Ca site can accommodate up to five H2 molecules through a Kubas-like interaction, with an average adsorption energy of -0.327 eV. With Ca atoms decorating both sides of the silicene, the system delivers a hydrogen storage capacity of 7.5 wt% and complete H2 release at approximately 380 K as revealed by AIMD simulations. Our findings suggest that Ca-decorated silicene could serve as a viable material for reversible hydrogen storage applications.