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 (MoO 3 ) 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, MoO 3 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 MoO 3 nanoribbons and then further enhance their hydrogen-ion storage performance. Remarkably, the W-doped MoO 3 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 MoO 3 nanoribbons and provide valuable insights for the design and development of high-performance electrode materials for hydrogen-ion batteries.