ABSTRACT
Tailoring the physicochemical properties of graphene through functionalization remains a major interest for next-generation technological applications. However, defect formation due to functionalization greatly endangers the intrinsic properties of graphene, which remains a serious concern. Despite numerous attempts to address this issue, a comprehensive analysis has not been conducted. This work reports a two-step fluorination process to stabilize the fluorinated graphene and obtain control over the fluorination-induced defects in graphene layers. The structural, electronic and isotope-mass-sensitive spectroscopic characterization unveils several not-yet-resolved facts, such as fluorination sites and CF bond stability in partially-fluorinated graphene (F-SLG). The stability of fluorine has been correlated to fluorine co-shared between two graphene layers in fluorinated-bilayer-graphene (F-BLG). The desorption energy of co-shared fluorine is an order of magnitude higher than the CF bond energy in F-SLG due to the electrostatic interaction and the inhibition of defluorination in the F-BLG. Additionally, F-BLG exhibits enhanced light-matter interaction, which has been utilized to design a proof-of-concept field-effect phototransistor that produces high photocurrent response at a time <200 µs. Thus, the study paves a new avenue for the in-depth understanding and practical utilization of fluorinated graphenic carbon.
ABSTRACT
TiO2 is the most studied photocatalyst because of its non-toxicity, chemical stability, and low cost. However, the problem of TiO2 is its low activity in the visible region of the spectrum. In this study, we focused on the preparation of composite photocatalytic materials with altered light absorption properties. TiO2 P25 and various metal oxides were mechanically joined by ball-milling and immobilized on glass plates. The prepared samples were evaluated based on their ability to degrade NO in gas phase. The formation of undesirable byproducts was also investigated. Four best performing composites were later chosen, characterized, and further evaluated under various conditions. According to their performance, the metal oxide additives can be divided into three groups. P25/Fe2O3 showed the most promising results-an increase in overall deNOx activity under modified ISO conditions and altered selectivity (less NO2 is formed) under both simulated outdoor and simulated indoor conditions. On the other hand, P25/V2O5 composite showed negligible photocatalytic activity. The intermediate group includes P25/WO3 and P25/ZnO photocatalysts, whose performances are similar to those of pristine P25.
Subject(s)
Oxides , Titanium , Titanium/chemistry , CatalysisABSTRACT
Contact resistance between electrically connected parts of electronic elements can negatively affect their resulting properties and parameters. The contact resistance is influenced by the physicochemical properties of the connected elements and, in most cases, the lowest possible value is required. The issue of contact resistance is also addressed in connection with the increasingly frequently used carbon allotropes. This work aimed to determine the factors that influence contact resistance between graphene prepared by chemical vapour deposition and pre-patterned Cu and Au electrodes onto which graphene is subsequently transferred. It was found that electrode surface treatment methods affect the resistance between Cu and graphene, where contact resistance varied greatly, with an average of 1.25 ± 1.54 kΩ, whereas for the Au electrodes, the deposition techniques did not influence the resulting contact resistance, which decreased by almost two orders of magnitude compared with the Cu electrodes, to 0.03 ± 0.01 kΩ.
ABSTRACT
Heterogeneous photocatalysis of TiO2 is one of the most efficient advanced oxidation processes for water and air purification. Here, we prepared hierarchical TiO2 layers (Spikelets) by hollow-cathode discharge sputtering and tested their photocatalytic performance in the abatement of inorganic (NO, NO2) and organic (4-chlorophenol) pollutant dispersed in air and water, respectively. The structural-textural properties of the photocatalysts were determined via variety of physico-chemical techniques (XRD, Raman spectroscopy, SEM, FE-SEM. DF-TEM, EDAX and DC measurements). The photocatalysis was carried out under conditions similar to real environment conditions. Although the abatement of NO and NO2 was comparable with that of industrial benchmark Aeroxide® TiO2 P25, the formation of harmful nitrous acid (HONO) product on the Spikelet TiO2 layers was suppressed. Similarly, in the decontamination of water by organics, the mineralization of 4-chlorophenol on Spikelet layers was interestingly the same, although their reaction rate constant was three-times lower. The possible explanation may be the more than half-magnitude order higher external quantum efficacy (EQE) compared to that of the reference TiO2 P25 layer. Therefore, such favorable kinetics and reaction selectivity, together with feasible scale-up, make the hierarchical TiO2 layers very promising photocatalyst which can be used for environmental remediation.
