Lithium rich layered oxide xLi2MnO3∙(1−x)LiMO2 (M = Mn, Co, Ni, etc.) materials are promising cathode materials for next generation lithium ion batteries. However, the understanding of their electrochemical kinetic behaviors is limited. In this work, the phase separation behaviors and electrochemical kinetics of 0.5Li2MnO3∙0.5LiCoO2 materials with various Li2MnO3 domain sizes were studied. Despite having similar morphological, crystal and local atomic structures, materials with various Li2MnO3 domain sizes exhibited different phase separation behavior resulting in disparate lithium ion transport kinetics. For the first few cycles, the 0.5Li2MnO3∙0.5LiCoO2 material with a small Li2MnO3 domain size had higher lithium ion diffusion coefficients due to shorter diffusion path lengths. However, after extended cycles, the 0.5Li2MnO3∙0.5LiCoO2 material with larger Li2MnO3 domain size showed higher lithium ion diffusion coefficients, since the larger Li2MnO3 domain size could retard structural transitions. This leads to fewer structural rearrangements, reduced structural disorders and defects, which allows better lithium ion mobility in the material.

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The effects of microwave and oxygen plasma treatments on the capacitive characteristics of a supercapacitor based on multiwalled carbon nanotubes (MWNTs) were investigated. MWNTs were heat-treated under air ambient at 500 °C for 1 h, and subsequently microwave-treated at 650 W for 70 s (m-MWNTs). Another batch of MWNTs was treated by oxygen plasma for 30 min (p-MWNTs). Pristine MWNTs, m-MWNTs, and p-MWNTs were separately used as electrode materials for supercapacitors. Their cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy results were analyzed. The p-MWNTs show the best performance with a specific capacitance of 238.23 F·g−1. The capacitance improvement is attributed to the increase in the number of oxygen-containing functional groups, as evidenced by Fourier transform-infrared spectroscopy and contact angle measurement. These results suggest that oxygen plasma treatment is a rapid and efficient method for oxygen functionalization.

We identify the effects of crystallinity and morphology of zinc oxide nanowires grown hydrothermally with ammonia addition on their physicochemical properties for capturing extracellular vesicles.

Nitrogen self-doped activated carbons with high surface area obtained via the direct activation of Samanea saman leaves for high energy density supercapacitors.

In this paper, a nitrogen dioxide (NO 2 ) gas sensor using nitrogen-doped double-walled carbon nanotubes (N-DWCNTs) with different types of nitrogen is demonstrated, and the sensor performance to the pyridinic nitrogen is related. The ratio of nitrogen is controlled by the temperature applied for the synthesis. It is found that the fabricated sensor from N-DWCNTs enable an approximately threefold improvement in NO 2 detection compared to the sensor from DWCNTs. Also, the improvement of sensor response of N-DWCNTs more depends on the pyridinic site than the other types of nitrogen, because it can strongly interact with the NO 2 molecule. The sensing mechanism is attributed to the charge transfer between the NO 2 molecule and the sensing materials (especially with pyridinic site), which shifts the Fermi level, resulting in a decrease of the electrical resistance. Furthermore, the relation between the sensor response and the concentration of NO 2 is derived based on Langmuir adsorption isotherm, and the calculated detection limit can be down to 0.14 ppm, which suggests that the N-DWCNTs-based sensor is a promising approach for low concentration NO 2 detection at room temperature.

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