Investigation Of Active Species Research Articles

Graphene-decorated novel Z-scheme Bi@MOF composites promote high performance photocatalytic desulfurization

The Z-scheme photocatalyst constructed based on bismuth-based metal oxides (BMO) and metal–organic frameworks (MOF) holds significant potential for effectively degrading odorous Reduced Sulfur Compounds (RSC) due to its robust redox capabilities. However, challenges such as lattice mismatch, interface defects, and rapid recombination of photogenerated charges substantially impede the Z- scheme charge transfer in BMO@MOF photocatalysts. In this research, graphene was introduced into the BiVO4@NH2-UiO-66 system as an electron bridge and co-catalyst to reduce the interfacial transfer resistance and increase the absorption of near-infrared light, resulting in superior degradability of RSCs compared to both the individual components and BiVO4@NH2-UiO-66. The incorporated graphene not only serves as the growth substrate for BiVO4 and NH2-UiO-66 but also plays a crucial role as an electron mediator in enhancing the vectorial charge transfer from BiVO4 to NH2-UiO-66. This strengthens the Z-scheme charge transfer pathway, suppressing bulk charge recombination, increasing overall carrier density, and maintaining robust redox capabilities. Additionally, the investigation of active species and key intermediate products was conducted to explore potential degradation pathways of RSCs. This work demonstrates a novel approach in promoting photocatalytic degradation of RSCs by harnessing the synergistic effects between doping and heterogeneous structures within the photocatalyst.

Investigation of active species in low-pressure capacitively coupled N2/Ar plasmas

In this paper, a self-consistent fluid model is developed focusing on the plasma parameters in capacitively coupled 20% N2–80% Ar discharges. Measurements of ion density are performed with the help of a floating double probe, and the emission intensities from Ar(4p) and N2(B) transitions are detected by an optical emission spectroscopy to estimate their relative densities. The consistency between the numerical and experimental results confirms the reliability of the simulation. Then the plasma characteristics, specifically the reaction mechanisms of active species, are analyzed under various voltages. The increasing voltage leads to a monotonous increase in species density, whereas a less homogeneous radial distribution is observed at a higher voltage. Due to the high concentration of Ar gas, Ar+ becomes the main ion, followed by the N2+ ion. Besides the electron impact ionization of neutrals, the charge transfer processes of Ar+/N2 and N2+/Ar are found to have an impact on the ionic species. The results indicate that adopting the lower charge transfer reaction rate coefficients weakens the Ar+ ion density and yields a higher N2+ ion density. However, the effect on the species spatial distributions and other species densities is limited. As for the excited-state species, the electron impact excitation of background gases remains overwhelming in the formation of Ar(4p), N2(B), and N2(a′), whereas the N2(A) molecules are mainly formed by the decay of N2(B). In addition, the dissociation of N2 collided by excited-state Ar atoms dominates the N generation, which are mostly depleted to produce N+ ions.

Investigation of active species in methanation reaction over cerium based loading

A series of cerium oxide based catalyst has been studied by various cerium loadings that calcined at 1000oC using wet impregnation method. The potential Ru/Mn/Ce (5:35:60) /Al2O3 catalyst calcined at 1000oC was characterized using XRD, XPS, and BET analyses. As could be observed from the XRD analysis, at Ce ratio of 55% and 65%, both revealed the presence of RuO2 with tetragonal phase and intense, sharper peaks indicating to high crystallinity and in line with lower surface area, 50.95 m2/g in BET analysis. Meanwhile, CeO2 (cubic phase) and MnO2 (tetragonal phase) were also observed for 55%, 60%, and 65%, respectively. However, the presence of Al2O3 with rhombohedral phase at 55% and 65% was revealed as an inhibitor which decreased the CO2 conversion. The presence of active species on Ru/Mn/Ce (5:35:60) /Al2O3 catalyst has been confirmed using XPS analysis with the deconvolation peaks belonged to Ce4+ with the formation of CeO2 compound and Mn4+ for MnO2. The product formed in catalytic methanation was proposed to be H2O and CH3OH from GC and HPLC analysis.

Direct reaction between silicon and methanol over Cu-based catalysts: investigation of active species and regeneration of CuCl catalyst.

When a CuCl/Si mixture was pretreated at 200–240 °C in a N2 atmosphere, trimethoxysilane was predominantly formed in the direct reaction of silicon with methanol. When the pretreatment temperatures were raised to 260–340 °C, tetramethoxysilane was favorably formed. The CuxSiyClz species catalyzed the reaction between silicon and methanol to trimethoxysilane. Chlorination of the spent CuCl/Si mixture promoted the reaction between silicon and methanol to form both trimethoxysilane and tetramethoxysilane due to the recovery of the CuCl phase and the exposure of the metallic Cu0 phase. When Cu2O, CuO, and Cu0 were used as the catalysts, tetramethoxysilane was formed as the main product.