Modeling of the structural, optoelectronic, thermodynamic, dynamical stability, and the hydrogen storage density of CsSnX3 (X ​= ​O, S, Se and Te) perovskites

Abstract

Based on density functional theory (DFT) approach, investigations on the structural, thermodynamic, electronic, optoelectronic, phonon, mechanical, and the hydrogen gravimetric storage density of CsSnX3 (X ​= ​O, S, Se and Te) perovskite systems is presented herein. While results of the computed lattice constant values for the investigated perovskite systems increased with an increase in the size of the anion X (X ​= ​O, S, Se, Te), the electronic bandgap values of 1.42, 1.02, 0.64, and 0.40 ​eV is obtained for CsSnO3, CsSnS3, CsSnSe3, and CsSnTe3 respectively. Among the studied systems, CsSnO3 and CsSnS3 are found to be dynamically stable, with CsSnO3 material being the most stable among the studied compounds owing to its frequencies in the real state of the phonon dispersion curve. To study the hydrogen storage properties of the materials in this present study: CsSnO3, CsSnS3, CsSnSe3, and CsSnTe3 the crystal structures have been modified by replacing the heteroatoms (O, S, Se, and Te) with hydrogens which is given as: CsSnO_H4, CsSnS_H4, CsSnSe_H4 and CsSnTe_H4. The gravimetric density (GD) suggests a strong agreement with the calculated band structure and decreases as the amount of band gap becomes enormous, where the CsSnO reveals a highest capacity of 0.74 which decrease as we go from O–Te for two atomic hydrogens. The CsSnTe shows the lowest gravimetric density of 0.526. Also, the formation energies obtained for CsSnO3_H4 estimated to be −31.599 ​kJ ​mol−1 ​has the highest energy however, these was observed to decrease as we go from oxygen to S ​> ​Se ​> ​Te. Moreover, the desorption temperature which is necessary for physical application reveals that the investigated materials are in line with the required range of desorption temperature for practical applications 289 ​K ​°K proposed by US-DOE, which implies that there are no barriers for hydrogen desorption from CsSnX3_H4 compounds. Therefore, it can be deduced that CsSnX3_H4 is a reversible hydrogen storage material. However, CsSnO3_H4 the best desorption temperature, this means that the presence of O atom in the perovskite improves the adsorption energy of interaction between the crystal lattice and the hydrogen molecules and decrease in the order of S ​> ​Se ​> ​Te respectively.