Enhanced Hydrogen-Ion Storage Performance of Molybdenum Trioxide Nanoribbons Doped by Oxygen Vacancies

Hydrogen ion has been extensively studied as a charge carrier in electrochemical energy storage devices due to its minimal ionic radius and abundant reserves. Among various candidate materials, molybdenum trioxide (MoO3) stands out as a promising electrode material owing to its excellent chemical stability and ultrahigh theoretical storage capacity. However, its practical application is hindered by a narrow potential window as a hydrogen-ion electrode and a low operating voltage caused by aqueous electrolyte decomposition. In this study, MoO3 nanoribbons with significant number of oxygen vacancies were synthesized via a simple hydrothermal method, which exhibit notable backward shift in the hydrogen evolution potential, three-proton intercalation/deintercalation process, and then a very noticeable enhancement in hydrogen-ion storage capacity during electrochemical testing in the aqueous electrolyte. It was also found that tungsten(W) doping in a specific amount can enrich the oxygen vacancies in MoO3 nanoribbons and then further enhance their hydrogen-ion storage performance. Remarkably, the W-doped MoO3 nanoribbons with a nominal molar ratio of 3% demonstrate an exceptional specific capacity of 390.8 mA h/g at a current density of 100 C (40 A/g). This study might highlight the significant impact of oxygen vacancy and tungsten(W) doping on the microstructures and electrochemical properties of MoO3 nanoribbons and provide valuable insights for the design and development of high-performance electrode materials for hydrogen-ion batteries.