Nguyen Duc Quang

NO gas sensing kinetics at room temperature under UV light irradiation of In 2 O 3 nanostructures

In2O3 nanostructure sensors were fabricated by arc-discharging a source composed of a graphite tube containing indium. The NO gas sensing properties, as well as the morphology, structure, and electrical properties, were examined at room temperature under UV light illumination. In particular, the response and recovery kinetics of the sensor at room temperature under various UV light intensities were studied. The maximum response signal was observed at an intermediate UV light intensity, which could be corroborated by a nano-size effect based on the conduction model of a resistive chemical nano sensor. The mechanism for the enhanced adsorption/desorption kinetics for NO in an air environment under UV light irradiation is discussed in detail. Furthermore, the general requirements of the sensor, including the stability, repeatability, and selectivity, are discussed.

Robust graphene-wrapped PtNi nanosponge for enhanced oxygen reduction reaction performance

We synthesize a graphene-wrapped 3D-PtNi nanosponge (G-PtNi NS) using formic acid as a reducing agent and carbon dots as a structure-directing agent at room temperature. Reduced Ni and Pt atoms initiate the exfoliation of carbon dots into graphene dots, which eventually encapsulate the PtNi nanocrystals. The strong Pt–carbon interaction propels the formation of the G-PtNi NS with large specific surface area and good long-term stability. The G-PtNi NS shows high reactivity for an oxygen reduction reaction (ORR). The ORR activity is maintained even after 3000 cycles. We confirm that the graphene layers physically stabilize the PtNi NS and chemically adjust the oxygen affinity of the PtNi NS, which both positively contribute to the ORR performance.

3D inverse-opal structured Li4Ti5O12 Anode for fast Li-Ion storage capabilities

Since the demand for high power Li-ion batteries (LIBs) is increasing, spinel-structured lithium titanate, Li4Ti5O12 (LTO), as the anode material has attracted great attention because of its excellent cycle retention, good thermal stability, high rate capability, and so on. However, LTO shows relatively low conductivity due to empty 3d orbital of Ti4+ state. Nanoscale architectures can shorten electron conduction path, thus such low electronic conductivity can be overcome while Li+ can be easily accessed due to large surface area. Herein, three dimensional bicontinuous LTO electrodes were prepared via close-packed self-assembly with polystyrene (PS) spheres followed by removal of them, which leads to no blockage of Li+ ion transportation pathways as well as fast electron conduction. 3D bicontinuous LTO electrodes showed high-rate lithium storage capability (103 mAh/g at 20 C), which is promising as the power sources that require rapid electrochemical response.