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排序方式: 共有119条查询结果,搜索用时 46 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(77):32928-32939
The development of efficient and stable electrocatalysts is of great significance for improving water splitting. Among them, transition metal oxyhydroxides show excellent performance in oxygen evolution reactions (OER), but there are certain difficulties in direct preparation. Recently, Metal–organic frameworks (MOFs) as precatalysts or precursors have shown promising catalytic performance in OER and can be decomposed under alkaline conditions. Therefore, using a mild and controllable way to convert MOFs into oxyhydroxides and retaining the original structural advantages is crucial for improving the catalytic activity. Herein, a rapid electrochemical strategy is used to activate well-mixed MOFs to prepare Co/Ni oxyhydroxide nanosheets for efficient OER catalysts, and the structural transformation in this process was investigated in detail by using scanning electron microscope, X-ray diffraction, Raman, X-ray photoelectron spectroscopy and electrochemical methods. It is discovered that electrochemical activation can promote ligand substitution of well-mixed MOFs to form porous oxyhydroxide nanosheets and tune the electronic structure of the metal (Co and Ni), which can lead to more active site exposure and accelerate charge transfer. In addition, the change of structure also improves hydrophilicity, as well as benefiting from the strong synergistic effect between multiple species, the optimal a-MCoNi–MOF/NF has excellent OER performance and long-term stability. More obviously, the porous CoNiOOH nanosheets are formed in situ during electrochemical activation process through structural transformation and acts as the active centers. This work provides new insights for mild synthesis of MOFs derivatives and also provides ideas for the preparation of highly efficient catalysts. 相似文献
2.
《Ceramics International》2015,41(7):8614-8622
SnO2–ZnO nanocomposite thin films, prepared by a simple carbothermal reduction based vapor deposition method, were irradiated with 8 MeV Si3+ ions for engineering the morphological and optical properties. The surface morphology of the nanocomposites was studied by atomic force microscopy (AFM), while the optical properties were investigated by photoluminescence spectroscopy (PL) and Raman spectroscopy. AFM studies on the irradiated samples revealed growth of nanoparticles at lower fluence and a significant change in surface morphology leading to the formation of nanosheets and their aggregates at higher fluences. A tentative mechanism underlying the observed ion induced evolution of surface morphology of SnO2–ZnO nanocomposite is proposed. PL studies revealed strong enhancement in the UV emissions from the nanocomposite thin film at lower fluence, while a drastic decrease in the UV emissions along with a significant enhancement in the defect emissions has been observed at higher fluences. 相似文献
3.
Huimin Zhao Wensi Wang Yunmei Du Yu Yang Minghui Wang Shaoxiang Li Ruixin Chen Yanru Liu Lei Wang 《International Journal of Hydrogen Energy》2021,46(18):10763-10772
In this work, we synthesized Se doped MoS2@Ni3S2 with nanosheets coated nanorods structure supported on Ni foam (MoNiSeS). Firstly, MoS2@Ni3S2 (MoNiS) nanorods was synthesized by hydrothermal method. After selenization treatment, MoSe2 successfully formed on the edge of MoS2 nanosheets and particle Ni3S2 transformed into NiSe, in which MoSe2 and NiSe acted as new phase in MoNiSeS. The obtained MoNiSeS only needs a low overpotential of 68 mV to reach the current density of 10 mA cm?2, and has a low Tafel plots of 72.77 mV dec?1 and good electrochemical durability, whose electrochemical activity is much better than that of MoNiS and NiSeS, implying the introduction of Mo and Se is beneficial to improve the electrocatalytic performance of NiS for HER. In addition, the proper amount of Mo source, which has an effect on the morphology of product, has also been investigated. For MoNiSeS, the typical nanosheets coated nanarods expose more active sites and the synergic effects is good to the improvement of the catalytic activity. Meanwhile, WNiSeS has also been prepared using the same method and the corresponding results show that the electrochemical activity of WNiSeS is much better than that of NiSeS, proving the universality of this strategy. 相似文献
4.
Jiarui HuangAuthor Vitae Youjie WuAuthor VitaeCuiping GuAuthor Vitae Muheng ZhaiAuthor VitaeYufeng SunAuthor Vitae Jinhuai LiuAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(1):126-133
Hierarchically three-dimensional (3D) porous ZnO architectures are synthesized by a template-free, economical aqueous solution method combined with subsequent calcination. First, the precursors of interlaced and monodisperse basic zinc nitrate (BZN) nanosheets are prepared. Then calcination of the precursors produces hierarchically 3D porous ZnO architectures composed of interlaced ZnO nanosheets with high porosity resulting from the thermal decomposition of the precursors. The products are characterized by X-ray diffraction, thermogravimetric-differential thermalgravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller N2 adsorption-desorption analyses. The BET surface area of the hierarchically porous ZnO nanostructures was calculated to be 12.8 m2 g−1. Compared with ZnO rods, the as-prepared porous ZnO nanosheets exhibit a good response and reversibility to some organic gases, such as ethanol and acetone. The responses to 100 ppm ethanol and acetone are 24.3 and 31.6, respectively, at a working temperature of 320 °C. These results show that the porous ZnO architectures are highly promising for gas sensor applications, as the gas diffusion and mass transportation in sensing materials are significantly enhanced by their unique structures. Moreover, it is believed that this solution-based approach can be extended to fabricate other porous metal oxide materials with a unique morphology or shape. 相似文献
5.
6.
《International Journal of Hydrogen Energy》2019,44(31):16110-16119
The activity of transition metal dichalcogenides (TMD) toward hydrogen evolution reaction (HER) derives from the active sites at the edges, but the basal surface still remain catalytic insert. Herein, ultrathin MoSSe alloy nanosheets array on multiwalled carbon nanotubes (MWCNTs) to form a core shell structure via a simple solvothermal process. These three-dimensional (3D) MoSSe hybrids show a high activity in hydrogen evolution reaction (HER) with a small Tafel slope of 38 mV dec−1 and a low overpotential of 102 mV at 10 mA cm−2. In addition, their HER activity remains remarkably stable without significant decay after 100 h polarization. Such superior catalytic HER activity springs from the 3D hierarchical heterostructure, which is abundant of catalytic edge sites, and the alloy effect between S and Se, which will create huge defects and strain to form vacancy sites on the basal plane. This strategy may open a new avenue toward the development of nonprecious high-performance HER catalysts. 相似文献
7.
《Ceramics International》2017,43(2):2069-2075
It is very important to develop a new synthetic route for lanthanide metal oxides with novel morphologies and having different fundamental properties and application performances. Here, we report Er2O3 nanorods and nanosheets prepared by a facile hydrothermal method followed by post-thermal annealing treatment. Thermal treatment of Er4O2(OH)8(HNO3) and Er2O5H4 was carried out to form the nanorods and nanosheets, respectively. Their physicochemical properties were evaluated by field-emission scanning electron microscopy, X-ray diffraction crystallography, high-resolution transmission electron microscopy, Fourier transform infrared (IR) spectroscopy, Ultraviolet-visible-near IR absorption spectroscopy, and X-ray photoelectron spectroscopy. The synthesis method and novel fundamental properties provide valuable information for the development of Er complexes and oxides. 相似文献
8.
《Ceramics International》2022,48(5):6157-6165
Electrochemical system centered on hierarchically carbon-based metal sulphide assemblies are of great fame for competent supercapacitors. Herein, the synthesis of a hierarchical CNT anchored MoS2–Bi2S3 nanocomposite is reported. Attractively, a vertically grown Bi2S3 nanorods supported on MoS2 nanosheets with carbon framework acts as a highly effective electrode in alkaline electrolyte. More interestingly, this hierarchical structure and synergetic upshot of CNT and composites provide excess coverage of active sites with improved conductivity and stability. Advancing from the physical and compositional properties of nanocomposites, the specific capacitance of MoS2–Bi2S3@CNT composites is measured to be 1338 F/g at 10 mV/s, columbic efficiency of 99.5% over 10000 cycles and long-term stability (60% retention at 0.5 A g?1 over 2000 cycles and 34.6% up to 10000 cycles). The success of this MoS2–Bi2S3@CNT composite may be attributed to the structural advantages, admirable cyclic stability, and better capacitance retention for supercapacitor applications. 相似文献
9.
Yongjun Zheng Rui Sun Zhaoxia Qin Xinlong Liu Yufei Zhang Haibin Wang Haosen Fan 《金属学报(英文版)》2022,35(8):1376-1382
Fe 2 O 3 /Co 3 O 4 /Ni O/NC nanosheets have been successfully prepared via a two-step annealing process of ternary metal coordination polymer. Attributing to the synergistic e? ects of the multiple metal oxides and the unique 2D nanosheet structure, the improved electrical conductivity and e? ective electron/ion transfer enables Fe 2 O 3 /Co 3 O 4 /Ni O/NC electrode to exhibit excellent electrochemical prope... 相似文献
10.
Ningning Guan 《Materials Letters》2009,63(15):1272-1274
Single-crystalline Fe3O4 nanosheets were obtained for the first time by simply adjusting the pH of a magnetite particle dispersion, using a hydrophilic terpolymer as stabilizer. We experimentally observed the magnetite nanoparticles spontaneous, template-free organization into nanosheets. This transformation occurs in an acidic environment at the zeta potential minimum by the abrupt, oriented self-assembly of polymer-stabilized magnetite particles at room temperature. The driving forces of the oriented self-assembly process includes the interplay of anisotropic dipolar forces, electrostatic interactions and isotropic van der Waals forces. 相似文献