Qun Ma,Zhigui Zhang,Pengzu Kou,Dan Wang,Zhiyuan Wang,Hongyu Sun,Runguo Zheng,Yanguo Liu
Two-dimensional layered MXene material with high conductivity and good mechanical flexibility has gained wide attention in the field of energy storage. However, the practical application of MXene was hampered by its limited specific capacity and the unstable structure. Herein, a composite of in-situ grown niobium-doped TiO 2 nanosheet arrays on a double transition metal MXene TiNbCT x (TiNbC@NTO) was successfully obtained via a hydrothermal pretreatment followed by in-situ partial oxidation strategy. The prepared TiNbC@NTO combines multiple advantages of both MXene and oxide, including high conductivity derived from the unoxidized MXene TiNbCT x , superior structure stability from the in-situ produced oxide between the MXene layers, which prevents structural collapse and restacking during charging and discharging, and the large layer space which promotes lithium-ion transport. The degree of oxidation of MXene can be adjusted by controlling the reaction temperature, and the oxide nonosheet turn dense with the increase of the temperature. All the oxidized MXenes show improved electrochemical performance compared with the pure TiNbCT x , and the TiNbC@NTO-500 with the appropriate degree of oxidation exhibits the highest reversible capacity, best cycling stability of 261 mAh g −1 after 500 cycles at 1.0 A g −1 among all the as-prepared composites. Furthermore, an extraordinary rate performance (148.5 mAh g −1 at 2 A g −1 ) was obtained based on the pseudocapacitance dominated mechanism. This work provides a new insight into improving the performance of MXene-based anode material for lithium-ion batteries.
This study explores an aerosol-assisted method to prepare an efficient support for the Pt catalyst of polymer electrolyte membrane fuel cells (PEMFCs). Titania nanoparticles and mesoporous niobium-doped titania nanoparticles were prepared by aerosol-assisted self-assembly using titanium(IV) isopropoxide and niobium(V) ethoxide as the titanium and niobium sources for application as non-carbon supports for the platinum electrocatalyst. The structural characteristics and electrochemical properties of the supports were investigated by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance, inductively coupled plasma optical emission spectrometry, and dynamic light scattering. The Brunauer–Emmett–Teller method was used to calculate the specific surface areas of the samples, and the pore size distribution was also examined. The results demonstrated that under a radial concentration gradient, the aerosol droplets self-assembled into a spherical shape, and mesoporous supports were obtained after subsequent removal of the surfactant cetyltrimethylammonium bromide by annealing and washing. The hydrothermal technique was then used to deposit platinum on the TiO2-based supports. The electrical conductivity of the non-carbon support was enhanced by the strong metal–support interaction effect between the platinum catalyst particles and the porous niobium-doped TiO2 support. The half-wave potential, electrochemical surface area, mass activity, and specific activity of the obtained Pt/Nb-TiO2 catalyst all surpassed those of commercial Pt/C.
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