First-principles study on the mechanism of Hf and Ti doping promoting hydrogen release in ZrCoH3

This paper reveals the mechanism of Hf and Ti doping promoting hydrogen release in ZrCoH₃. Different from previous experimental methods, this study employs the plane wave pseudopotential method and density functional theory to predict the relationship between the formation energy and electronic structure of the ZrCoH₃-Hf/Ti system, and uses theoretical calculations to guide the modification design of ZrCoH₃. Firstly, by calculating the thermodynamic properties of the ZrCoH₃-Hf/Ti system and combining the density of states theory, the bonding characteristics and dehydrogenation preference between H atoms and neighboring metal atoms in the ZrCoH₃-Hf/Ti system are determined. Additionally, the electronic structure of the ZrCoH₃-Hf/Ti system is calculated to elucidate the hybridization of bonding and antibonding orbitals between atoms in the ZrCoH₃-Hf/Ti system. Moreover, D_Co-d is utilized to measure the strength of antibonding interactions in the ZrCoH₃-Hf/Ti system. The main cause of antibonding interactions in the ZrCoH₃-Hf/Ti system is attributed to the variation in formation energy, and the change in antibonding interactions is sensitive to the variation in formation energy. Finally, a feasible method to improve the properties of ZrCoH₃ is proposed, which involves modifying the electronic structure to increase the partial density of states at the Fermi energy level, making the formation energy of hydrides less negative and forcing the structure to be more unstable. This method has potential application value in the modification of ZrCoH₃.