Ti 3 C 2 T x nanosheets are attractive for electromagnetic wave absorption (EMA) materials requiring ultra-thin and high-performance due to their high conductivity and polarizability. However, the self-restacking of Ti 3 C 2 T x nanosheets unavoidably decreases the number of active sites, specific surface area, and conductivity. Herein, a simple strategy is developed to prepare a core–shell structure of SiO 2 @Ti 3 C 2 T x by electrostatic assembly and hydrogen bonding. SiO 2 spheres as templates cannot only prevent Ti 3 C 2 T x nanosheets from further stacking, but also modulate the surface impedance and significantly increase interfacial polarization loss. The resulted SiO 2 @Ti 3 C 2 T x composite can deliver superior absorption capacity with minimum reflection coefficient (RL) of −58.01 dB at an ultra-thin thickness of only 1.3 mm. The absorption efficiency is calculated over 99.999 % with an effective absorption bandwidth (EAB) of 3.44 GHz. Furthermore, with increasing amounts of SiO 2 templates, the EAB can be broadened up to 15.04 GHz (2.96–18 GHz) in the thickness range of 1–3 mm. The absorption mechanisms are described based on multiple reflection, polarization behaviors, tunable impedance matching, and conduction loss. The present work could pave a way for obtaining ultra-thin, high-performance MXene-based EMA materials.
The sluggish kinetics of oxygen evolution reaction (OER) is the most challenging technical problem in water splitting. Here, we reported a new type of cauliflower-like NiCo 2 O 4 (CF-NiCo 2 O 4 ) film which was co-electrodeposited with silica for oxygen evolution reaction. Structure and morphology of the obtained films were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy . Electrochemical properties of the CF-NiCo 2 O 4 film were evaluated by quasi-steady state polarization curve , cyclic voltammetry and electrochemical impedance spectroscopy . Results show that the enhanced electrocatalytic activity of the CF-NiCo 2 O 4 film toward OER is a synergistic effect of improved intrinsic catalytic activity and increased surface area.
With SiO 2 spheres as the template and PPy as carbon precursor, a layer of amorphous carbon has been tightly coated on NiCoO 2 -CoOOH hollow burr nanospheres, forming a unique double-shelled hollow burr nanospheres structure. Carbon@NiCoO 2 -CoOOH presents a high discharge capacity (1334 mAh g −1 at a current density of 100 mA g −1 ), a stable cycling performance (912 mAh g −1 at the 600th cycle at 200 mA g −1 ), and a desirable rate capability when used as anode material for lithium-ion batteries. The outstanding electrochemical performance results from the synergy effect of the hollow burr nanosphere and the amorphous carbon shell. The hollow burr nanosphere endows NiCoO 2 and CoOOH with a high electrochemical activity and a good accommodation capability to volume change. The amorphous carbon shell remarkably reinforces the structure stability and electronic conductivity of NiCoO 2 and CoOOH.
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