Mesoporous ultrafine Ta2O5 nanoparticle with abundant oxygen vacancies as a novel and efficient catalyst for non-aqueous Li-O2 batteries

Tailored Plasmonic Ru/OV-MoO2 on TiO2 Catalysts via Solid-Phase Interface Engineering: Toward Highly Efficient Photoassisted Li-O2 Batteries with Enhanced Cycling Reliability

The photoassisted electrochemical reactions are considered an effective method to reduce the overpotential of Li-O₂ batteries. However, achieving long-term cell cycling stability remains a challenge. Here, we report a solid-phase interfacial reaction (SPIR) strategy that introduces both oxygen vacancies (O_V) and metal centers (Ru) into the MoO₂ to synthesize the surface plasmon (i.e., Ru/O_V-MoO₂). Then, Ru/O_V-MoO₂ can be uniformly loaded on the TiO₂ nanowires by the hydrothermal method. The plasma effect of Ru/O_V-MoO₂ demonstrates the effective reduction of the photoexcited electron and hole recombination to improve visible light-harvesting ability. The lifetime of electrons and holes can be extended by Ru nanoparticles, which is beneficial for promoting the formation and decomposition of Li₂O₂. In addition, the generated O_V further enhanced the migration of electrons and Li⁺, thus improving the ORR performance. The Ru/O_V-MT/CC cathode corroborates excellent stability and catalytic performance in the photoassisted Li-O₂ battery, with an overpotential value of 0.47 V, achieving the highest energy efficiency of 93.94%, retaining at 89.13% after 800 h. This work offers a platform for preparing a stable, bifunctional catalyst with the high total activity of a photoassisted Li-O₂ battery.

17O Solid-State NMR Studies of Ta2O5 Nanorods

17O solid-state NMR spectroscopy was used to study the structure of Ta2O5 nanorods for the first time. Although the observations of oxygen ions in the "bulk" part of the Ta2O5 nanorods can be achieved with conventional high-temperature enrichment with 17O2, low-temperature isotopic labeling with H2 17O generated samples whose surfaces are selectively enriched, leading to surface-only detection of oxygen species. By applying 17O-1H double-resonance NMR techniques and 1H NMR spectroscopy, surface hydroxyl species and adsorbed water can also be studied. The results form the basis for further understanding of the structure-property relationship of Ta2O5 nanomaterials.

Amorphous Mo-Ta Oxide Nanotubes for Long-Term Stable Mo Oxide-Based Supercapacitors

With a large-scale usage of portable electric appliances, a high demand for increasingly high-density energy storage devices has emerged. MoO₃ has, in principle, a large potential as a negative electrode material in supercapacitive devices due to high charge densities that can be obtained from its reversible redox reactions. Nevertheless, the extremely poor electrochemical stability of MoO₃ in aqueous electrolytes prevents a practical use in high capacitance devices. In this work, we describe how to overcome this severe stability issue by forming amorphous molybdenum oxide/tantalum oxide nanotubes by anodic oxidation of a Mo-Ta alloy. The presence of a critical amount of Ta oxide (>20 at. %) prevents the electrochemical decay of the MoO₃ phase and thus yields an extremely high stability. Due to the protection provided by tantalum oxide, no capacitance losses are measureable after 10,000 charging/discharging cycles.