ABSTRACT
It is vital to have high sensitivity in gas sensors to allow the exact detection of dangerous gases in the air and at room temperature. In this study, we used 2D MXenes and MoS2 materials to create a Ti3C2-MoS2 composite with high metallic conductivity and a wholly functionalized surface for a significant signal. At room temperature, the Ti3C2-MoS2 composite demonstrated clear signals, cyclic response curves to NO2 gas, and gas concentration-dependent. The sensitivities of the standard Ti3C2-MoS2 (TM_2) composite (20 wt% MoS2) rose dramatically to 35.8%, 63.4%, and 72.5% when increasing NO2 concentrations to 10 ppm, 50 ppm, and 100 ppm, respectively. In addition, the composite showed reaction signals to additional hazardous gases, such as ammonia and methane. Our findings suggest that highly functionalized metallic sensing channels could be used to construct multigas-detecting sensors that are very sensitive in air and at room temperature.
Subject(s)
Molybdenum , Titanium , Ammonia , Gases , Molybdenum/toxicity , Titanium/toxicityABSTRACT
ZIF-8 is a highly porous, stable, and abundant surface area material that can be used as an environmentally friendly catalyst for Knoevenagel condensations. The effects of the ratio of the reactants (benzaldehyde (BA):ethyl cyanoacetate (ECA)), reaction temperature, and catalyst concentration were systematically investigated using a ZIF-8 catalyst and water as the solvent. ZIF-8 (3-5 wt%) showed excellent catalytic performance with an almost complete conversion of BA in less than 6 h with a BA:ECA molar ratio of 1:2 at different temperatures. At 60 °C, the BA conversion rate and product selectivity of the reaction reached their highest values after 4 h with a BA:ECA molar ratio of 1:1. When employing 5.0 wt% ZIF-8, almost complete BA conversion was achieved after 3 h at room temperature. ZIF-8 also demonstrated good recyclability with almost no change in its catalytic activity over five cycles. The proposed reaction mechanism is based on the catalytic activity of the basic N sites on the surface of ZIF-8, and is supported by density functional theory calculations. The present approach provides a promising strategy for the construction of simple and environmentally friendly ZIF-8 catalysts.
Subject(s)
Zeolites , Catalysis , PorosityABSTRACT
Photocatalytic hydrogen (H2) generation derived by water has been considered as a renewable energy to solve environmental problems and global energy crises. Thus, it is necessary to explore the most effective photocatalysts by using multi-cocatalysts, due to an intimate interaction between different components. Therefore, we already synthesized the TiO2/Ti3C2/g-C3N4 (TTC) photocatalyst from g-C3N4 and Ti3C2 MXene via a calcination technique, and applied this composite for H2 evolution. By making use of titanium atom from Ti3C2 MXene, titanium dioxide (TiO2) was in-body developed, which leads to form a close heterostructure between metallic material and semiconductors. Besides, g-C3N4 amorphous with highly surface area also contributes to harvest light irradiation during photocatalytic activity. The optimized TTC-450 heterostructure showed a super H2 generation efficiency than those of pure g-C3N4 and other samples. Besides, TTC-450 sample also exhibited great recyclability after 4 runs. The proposed mechanism illustrates the efficient movement of generated electrons in TTC system, which leads to high H2 evolution efficiency. Moreover, the obtained results consistently emphasize the TiO2/Ti3C2/g-C3N4 composite would be a unique material for H2 production and broaden applications of MXene materials.