Lattice-Structure-Dependent Hydrogen Ion Storage Performance of Molybdenum Trioxide Nanowires

Aqueous hydrogen ion batteries are emerging as a promising solution for large-scale energy storage due to their smallest ionic size and abundant availability. Among various materials, molybdenum trioxide has garnered significant attention for its rapid hydrogen ion insertion/extraction kinetics and high theoretical storage capacity. However, the mechanisms underlying the swift ion transport and high-capacity storage in MoO3 remain insufficiently understood, which necessitates further investigation to fully explore its potential applications in energy and information technologies. In this study, the electrochemical behavior of the hexagonal and orthorhombic MoO3 nanowires with nearly identical morphologies synthesized via the hydrothermal method has been thoroughly characterized, which exhibits lattice structure-sensitive hydrogen ion storage performance. The experimental results demonstrate that the charge storage process transitions from a capacitive- to diffusion-controlled mechanism, and the storage capacity increases from 155 to 279.6 mA h/g at a current density of 100 C when the lattice structure of the MoO3 nanowires gradually changes from hexagonal to orthogonal. The α-MoO3 nanowire electrode exhibits reduced polarization, a lower interfacial barrier, and higher ion diffusion coefficients, which might be attributed to the differences in the lattice structure. In the lattice of h-MoO3, the hydrogen ion storage sites are mainly distributed within the internal hexagonal channels, while α-MoO3 can offer much more instantly accessible storage sites due to its open structure vertical to the nanowire axis formed based on van der Waals force. Consequently, this study provides some insights into the rapid transport and large capacity storage of hydrogen ions in the MoO3 lattice and then suggests a mechanism for regulating hydrogen ion transport and storage for fast and high-capacity storage of energy.