RESUMO
The environmental suitability of hydrogen storage materials is significantly influenced by the way aluminum reacts synchronously with water, ice, and water steam. The straightforward ball milling process was used to synthesize Al-based composite materials with carbon nanotubes (CNTs) or graphene oxide (GO). The reactivity of the composites in various types of water was investigated. The Al/Bi/CNT and Al/Bi/GO composites may react in liquid water, low-temperature ice, and high-temperature steam. The hydrolysis promotion of Al-based composites by CNTs is superior to that of GO, whether in liquid water at 20 °C or ice at -20 °C. The maximum hydrogen generation rate of Al/Bi/CNT composites can reach 34.6 mL g-1 s-1 at 20 °C. The hydrogen generation volume of Al/Bi/CNT can reach 700 mL g-1 in 15 min on ice at -20 °C. Moreover, the ignition temperature and ignition delay time of Al/Bi/CNT are shorter than those of Al/Bi/GO in high-temperature steam. The hydrogen generation volume from Al/Bi/CNT at 200 °C can reach 853 mL g-1. These may originate from the unique one-dimensional nanostructure of CNTs, which provides more surface area or reaction sites during the hydrolysis of the composite.
RESUMO
The poor structural stability and conductivity of Na3V2(PO4)3 (NVP) have been serious limitations to its development. In this paper, Sc3+ is selected to replace partial site of V3+ which can enhance its ability to bond with oxygen, forming the ScO6 octahedral unit, resulting in improved structural stability and better kinetic properties for the NVP system. Moreover, due to the larger ionic radius of Sc3+ compared to V3+, moderate Sc3+ substitution can support the crystal framework as pillar ions and expand the migration channels for de-intercalation of Na+, thus efficiently promoting ionic conductivity. The introduction of polyacrylonitrile (PAN) to provide an N-doped porous carbon substrate is another key aspect. The low-cost carbon resource of PAN can induce a beneficial nitrogen-doped carbon skeleton with defects, enhancing electronic conductivity at the interface to reduce the polarization phenomenon. The established pore structure can serve as a buffer for unit cell deformation caused by Na+ migration. Furthermore, the enlarged specific surface area provides more active sites for electrolyte infiltration, improving the material utilization rate. The after cycling X-ray Diffraction/scanning electron microscope (XRD/SEM) further confirms the stabilized porous carbon skeleton and improved crystal stability of Sc-3 material. Ex-situ XRD analysis shows that the crystal volume change in the Sc-3 cathode is relatively slight but reversible during the charge/discharge process, indicating that Sc3+ doping plays a crucial role in stabilizing the unit cell structure. The hybrid Sc/VO6 and PO4 units jointly build a strong bone structure to resist stress and weaken deformation. Accordingly, the optimized Sc-3 sample reveals an initial capacity of 115.9 mAh/g at 0.1C, with a capacity retention of 78.6 % after 2000 cycles at 30C. The Sc-3//CHC full battery can release a capacity of 191.3 mAh/g at 0.05C, accompanied by successful illumination, showcasing its promising practical applications.
