Jiabin Wu

Flexible Transparent Molybdenum Trioxide Nanopaper for Energy Storage.

A flexible transparent molybdenum trioxide nanopaper, assembled via ultralong molybdenum trioxide nanobelts, displays an excellent average transmittance of ≈90% in the visible region. The free-standing nanopaper electrode delivers an outstanding specific capacitance of 1198 F g(-1) and shows an excellent long-term stability performance over 20 000 cycles with a retention rate of 99.1%.

Salt-Templated Synthesis of 2D Metallic MoN and Other Nitrides

Two-dimensional (2D) transition-metal nitrides just recently entered the research arena, but already offer a potential for high-rate energy storage, which is needed for portable/wearable electronics and many other applications. However, a lack of efficient and high-yield synthesis methods for 2D metal nitrides has been a major bottleneck for the manufacturing of those potentially very important materials, and only MoN, Ti4N3, and GaN have been reported so far. Here we report a scalable method that uses reduction of 2D hexagonal oxides in ammonia to produce 2D nitrides, such as MoN. MoN nanosheets with subnanometer thickness have been studied in depth. Both theoretical calculation and experiments demonstrate the metallic nature of 2D MoN. The hydrophilic restacked 2D MoN film exhibits a very high volumetric capacitance of 928 F cm-3 in sulfuric acid electrolyte with an excellent rate performance. We expect that the synthesis of metallic 2D MoN and two other nitrides (W2N and V2N) demonstrated here will provide an efficient way to expand the family of 2D materials and add many members with attractive properties.

Highly conductive and flexible molybdenum oxide nanopaper for high volumetric supercapacitor electrode

Paper-like electrodes with high conductivity and flexibility hold great potential for assembling high-performance flexible electronic devices. In this study, a flexible conductive film was fabricated via vacuum filtration using highly conductive MoO3−x ultralong nanobelts. This film has low sheet resistance of 5.1 Ω sq−1 and exhibits a stable three-dimensional structure even under 1000 times of bending test. Significantly, this free-standing film has a high volumetric capacitance of 652 F cm−3. Moreover, a symmetric device based on this electrode demonstrates good cycling stability with a capacitance retention of 85.7% after 25000 cycles. We anticipate that this strategy can also be applied to other three-dimensional flexible porous films based on one-dimensional conductive nanostructure, which could open up new opportunities for energy storage and conversion.

Band gap engineering of MnO2 through in situ Al-doping for applicable pseudocapacitors

Band gap engineering was achieved by in situ doping method for high electrical conductivity and chemical activity of MnO2. By in situ releasing and adsorption during electrodeposition, Al3+ with close ion radius to Mn4+ could replace the position of Mn4+ in MnO2. The in situ doping process brings impurity level in MnO2 and changes the energy band structure. The narrower band gap of MnO2 after Al doping with higher electron concentration on conduction band could improve the conductivity of MnO2. The specific capacitance of Al-doped MnO2 achieves 430.6 F g−1 which is almost 2.5 times of the capacitance of initial MnO2 (177 F g−1), shedding light on its practical applications.

Sulfur dioxide gas-sensitive materials based on zeolitic imidazolate framework-derived carbon nanotubes

Novel sensing materials that combine high sensitivity and selectivity as well as proper working temperature are essential for advanced gas detection applications. Metal organic framework (MOF)-based materials are promising candidates for many applications including gas sensing, but they exhibit some limitations such as a low electrical conductivity and high operating temperature, which have to be overcome. Herein, we demonstrate the synthesis of gas-sensing materials for sulfur dioxide, namely, carbon nanotube networks based on zinc-doped zeolitic imidazolate frameworks (ZIF-67) (bimetallic MOFs). The particles synthesized via bimetal co-doping of cobalt and zinc and the pyrolysis process possess a porous polyhedral morphology with abundant interconnecting carbon nanotubes (CNTs) on the surface, which results in significant sensitivity, cross-selectivity and durability towards SO2 at room temperature. This approach combines the advantages of both MOFs and CNTs. First-principles calculations further elucidate that the doped zinc embedding on the nanotube changes the SO2 adsorption level to a narrow p accepting level, which increases the hole carrier concentration remarkably and subsequently improves the conductivity to a large extent, thus providing excellent sensing performance with respect to the target gas.