Lilong Jiang

Additive-free synthesis of unique TiO2 mesocrystals with enhanced lithium-ion intercalation properties

Unique nanorod-like mesocrystals constructed from ultrathin rutileTiO2 nanowires were successfully fabricated for the first time using a low-temperature additive-free synthetic route, and the mesocrystal formation requirements and mechanism in the absence of polymer additives were discussed. The ultrathin nanowires were highly crystalline and their diameters were found to be ca. 3–5 nm. The rutile TiO2 mesocrystals were formed through homoepitaxial aggregation of the ultrathin nanowiresvia face-to-face oriented attachment, accompanied and promoted by simultaneous phase transformation from the precursor hydrogen titanate to rutile TiO2. The rutile TiO2 mesocrystals thus synthesized were subjected to detailed structural characterization by means of scanning and transmission electron microscopy (SEM/TEM) including high-resolution TEM (HRTEM) and selected area electron diffraction (SAED), X-ray diffraction (XRD) and Raman spectroscopy. The rutile TiO2 mesocrystals were tested for lithium-ion intercalation and demonstrated large reversible charge–discharge capacity and excellent cyclic stability, which could be attributed to the intrinsic characteristics of the mesostructured TiO2 constructed from ultrathin nanowires offering large specific surface area for intercalation reaction and easy mass and charge transport, as well as sufficient void space accommodating volume change.

Complex spinel titanate nanowires for a high rate lithium-ion battery

Complex spinel titanate Li2MTi3O8 (M = Co, Zn, Co0.5Zn0.5) nanowires have been synthesized via a simple synthetic route using titanate nanowires as a precursor. The nanowires are highly crystalline and have been used for the first time as the anode material in a rechargeable lithium-ion battery. The battery has exhibited a highly reversible charge-discharge capacity and excellent cycling stability, even at a current density as high as 3.2 A g−1. This result can be attributed to the intrinsic characteristics of spinel Li2MTi3O8 nanowires. A three-dimensional network could provide a diffusion space for lithium ion insertion into and extraction from the anode material, resulting in very good cycle performance, even at a high rate.

SPINEL Li2MTi3O8(M = Mg, Mg0.5Zn0.5) NANOWIRES WITH ENHANCED ELECTROCHEMICAL LITHIUM STORAGE

Spinel structural Li2MTi3O8(M = Mg, Mg0.5Zn0.5) nanowires have been successfully synthesized using titanate nanowires as a precursor and then have been used for the first time as anode materials in a rechargeable Li-ion battery. The cell composed of Li2MgTi3O8 nanowires exhibited a discharge capacity of 232 mAhg-1 at the second cycle, while only 159 mAhg-1 was obtained for the bulk prepared by a solid state reaction. The results of electrochemical impedance spectra indicate that spinel structural Li2MTi3O8(M = Mg, Mg0.5Zn0.5) nanowires can significantly reduce the charge transfer impedance, leading to enhanced capability of electrochemical lithium storage.

Insights into the high performance of Mn-Co oxides derived from metal-organic frameworks for total toluene oxidation

Mn-Co mixed metal oxide is considered as efficient catalyst for the total oxidation of volatile organic compounds. In this study, nanocube-like metal-organic frameworks (Mn3[Co(CN)6]2·nH2O) are adopted as the precursor to generate Mn-Co oxides with different Mn/Co molar ratios, which affect little on phase structure and textural properties. The obtained MOF-Mn1Co1 with uniform metal dispersion is rich in high valence of surface Mn4+ and Co3+ species, leading to high low-temperature catalytic activity of total toluene oxidation. The results of toluene-TPD followed by TPO and toluene-TPSR match well with the catalytic performances of MOF-Mn1Co1, MOF-Mn1Co2, and MOF-Mn2Co1, and in situ FITR proves that the benzoate route exists over MOF-Mn1Co1. It is found that a moderate ratio of Mn/Co (1:1) favors good low-temperature reducibility and high Oads/Olatt, resulting in superior oxidation performance. However, the stability in the existence of water for MOF-Mn1Co1 is not satisfied, which should be overcome in the future.

Synthesis of Co–Mn oxides with double-shelled nanocages for low-temperature toluene combustion

In this paper, we report a template-engaged strategy for the synthesis of Co–Mn oxides with double-shell box-in-box hollow nanocage (BHNC) structures. The inner shell of the box is made of Co3O4, while the outer shell is made of Co–Mn oxides. The composition of the outer shell was tuned by changing the Mn/Co molar ratio. This facile method can be used to construct box-in-box hollow structures of other transition metal oxides such as those of Co–Ni, Co–Cu and Co–Fe. These Co–Mn oxides with BHNCs exhibit toluene conversions over 90% at 250 °C, which is much higher than those of Co3O4 nanocages (NCs) and the traditional Co3O4-CP synthesized by co-precipitation method at the same temperature. Moreover, the former is superior to the latter in terms of resistance towards H2O and CO2. The superior catalytic performance of Co1Mn1 BHNCs is attributed to the high mobility of lattice oxygen, low toluene desorption temperature and active Co3+ sites originated from the oxidation of Co2+ by Mn3+.