Advanced Theoretical Engineering of KM3H9 (M = Fe, Co, Ni, Cu) Hydrides for Novel Applications in Hydrogen storage

Abstract

The drive for sustainable and efficient hydrogen storage technologies constitutes a critical challenge in the worldwide energy transition. This study presents a first-principles investigation of innovative K-based perovskite hydrides KM3H9 (M = Fe, Co, Ni, Cu), examined here for the inaugural time as prospective solid-state hydrogen storage materials. We extensively investigate their structural, electronic, optical, magnetic, mechanical, thermodynamic, and hydrogen storage properties utilizing density functional theory (DFT) inside the CASTEP framework. All four hydrides crystallize in a cubic perovskite phase and have negative formation energies, which show that they are thermodynamically stable. Phonon dispersion curves also show that they are dynamically stable. The examination of the electronic structure shows that it conducts electricity, which is good for hydrogen diffusion kinetics. Charge density mapping shows that there is a combination of ionic and covalent bonds. Optical tests show that there is considerable absorption in the far-ultraviolet range, which suggests that this material could be used in optoelectronic devices. Calculations that take into account spin polarization show that the series has antiferromagnetic ordering. Mechanical investigation shows that the compounds are stable yet brittle, and that their elastic responses are not the same in all directions. Thermodynamic tests show that stability is maintained at high temperatures, and hydrogen storage tests show that the system has good gravimetric and volumetric capacities with the right desorption temperatures. These results show that KM3H9 (M = Fe, Co, Ni, Cu) is a good candidate for next-generation solid-state hydrogen storage. They also have other useful features that could make them useful in optoelectronic and energy-related technologies.