High Oxidation Properties Research Articles

Photodeposition synthesis of hollow g-C3N4/Ag nanotubes with high oxidation properties to enhance visible-light photocatalytic performance

A hollow Ag-deposited g-C3N4 nanotube (CNNT/Ag) with high oxidation properties was synthesized using a simple photodeposition method. The g-C3N4 nanotubes provided abundant active sites and a large specific surface area for effective deposition of Ag nanoparticles. The Ag NPs expanded the light absorption range of g-C3N4 through surface plasmon resonance (SPR) effects and acted as an electron acceptor, effectively inhibiting the recombination of photogenerated carriers, thereby improving the charge separation efficiency. The CNNT/Ag composites exhibited excellent photocatalytic performance in the visible light degradation of rhodamine B and tetracycline, 6.42 and 2.16 times higher than pure g-C3N4, respectively. The increased photocatalytic activity of CNNT/Ag composites was attributed to the synergistic electron transfer interface between CNNT and Ag NPs, promoting the migration efficiency of photo-generated carriers. This work presented a promising strategy for constructing effective photocatalysts for degrading organic pollutants using morphology optimization and SPR effects on noble metal surfaces.

Constructing defect engineered 2D/2D MoO3/g-C3N4 Z-scheme heterojunction for enhanced photocatalytic activity

Photocatalytic redox technology is established in energy and environmental governance with its environmentally friendly and broad-based optical source. However, the development of photocatalysts with strong redox ability still remains urgently desirable. Herein, an oxygen vacancy-engineered 2D/2D Z-scheme heterojunction photocatalytic materials of MoO3/g-C3N4 are synthesized, which achieves a trade-off between the value band position of MoO3 with high oxidation property and the conduction band position of g-C3N4 with high reduction property. The 2D/2D heterojunction manifests excellent functionality for photocatalytic H2 evolution and tetracycline degradation. Particularly, 3 % MoO3/g-C3N4 provides the optimum H2 generation rate (328.75 μmol g−1 h−1) without any noble metal cocatalyst, which is about 87-fold higher than that of pure g-C3N4 (3.78 μmol g−1 h−1). Moreover, the TC degradation kinetic constant of 3 % MoO3/g-C3N4 (0.0196 min−1) is about 8.28 times of pure g-C3N4 (0.0023 min−1). The outstanding photo-catalytic ability mainly comes from the interfacial interaction between 2D MoO3 and 2D g-C3N4, which can shorten the transport distance of charge carriers and contribute abundant active sites to improve the separation efficiency of photogenerated carriers. Furthermore, the oxygen vacancies (OVs) strengthen the redox potential of the system and serve as effective trapping sites for photogenerated carriers to reduce the quenching rate of photogenerated electrons. This work provides a feasible strategy to develop 2D/2D Z-scheme photocatalytic systems with high photocatalytic performance on energy storage and environmental application.

Insights into co-doping effect of Sm and Fe on anti-Pb poisoning of Mn-Ce/AC catalyst for low-temperature SCR of NO with NH3

A novel anti-Pb poisoning Sm and Fe co-doped Mn-Ce/AC catalyst was prepared by impregnation method for low-temperature NH3-SCR of NO reaction. Maintaining the excellent low-temperature activity of Mn-Ce/AC catalyst, Sm and Fe co-doping remarkably enhanced the catalyst’s Pb-resistance with NO conversion up to 77%. Sm and Fe co-doped poisoning-catalysts exhibited large specific surface area and pore volume, and the crystallinity of the MnOx and CeOx reduced. The redox properties and surface acidity of the lead poisoned SmFeMnCe/AC catalyst were effectively retained, which could promote NO oxidation and NH3 activation, further benefiting the SCR reaction. In situ DRTFTS results indicated that the low-temperature NH3-SCR mechanism of all poisoned catalysts followed both L-H mechanism and E-R mechanism, and the L-H mechanism was dominated. On the one hand, the extraordinary lead resistance of Sm weakened the damage of lead species on the physicochemical properties of the catalyst; on the other hand, the high oxidation properties and surface acidity of Fe enhanced the catalytic activity of the poisoned catalyst. Finally, a possible synergistic mechanism model of Sm and Fe co-doping on Mn-Ce/AC catalyst against Pb-poisoning was proposed.

Shrinked bifilms in Mg-Gd-Y-Zr alloy

Mg-Gd-Y-Zr alloy has excellent mechanical properties at room and high temperatures, but its high oxidation properties can also result in a significant number of bifilm defects. However, its formation mechanism was not revealed so far, which was explored in the present work. The results showed that the surface oxide film folds into a grid-like double layer structure defect during solidification, due to the difference of thermal expansion coefficient between surface oxide film and matrix. In addition, the oxide film produces microcracks. As the magnesium alloy melt fills the crack, Zr precipitates into crystal nucleus with peritectic reaction and Y2O3 accumulates. These results would shed new lights on the understanding of shrinkage formation of bifilm defects and improving the defects control of magnesium alloy castings.

High-oxidation-governed fluid evolution in the Naruo porphyry Cu-Au deposit, Tibet, China

The Naruo porphyry Cu-Au deposit is the third discovered large deposit in the Duolong metallogenic district. ‘Previous research has mainly focused on the geochemistry of the ore-bearing granodiorite porphyry; however, the metallogenesis is also poorly understood. Based on mapping using outcrops and geological drill cores, the alteration zones were outlined and the sequence of veins was also identified. Furthermore, fluid inclusion microthermometry and Raman composition analyses were conducted.A boiling fluid system is indicated by the coexisting aqueous, brine and vapor inclusions in all vein types. Daughter-metal minerals bearing brine inclusions are the major fluid inclusion types in all veins, suggesting that the Naruo porphyry Cu-Au deposit was formed by high-salinity fluids; thus, the measured data of the brine inclusions are mainly used for the interpretation of fluid evolution. In the early quartz-magnetite veins, brine fluid inclusions exhibit high homogenization temperatures (greater than 500 °C) and diverse salinities (30.1–61.5 wt% NaCl equiv), while in the later magnetite-absent, chalcopyrite-bearing quartz–sulfide veins, the homogenization temperatures of aqueous and brine inclusions are below 440 °C, suggesting that the magnetite mostly precipitated at temperatures higher than 440 °C. In the even later quartz–pyrite ± chalcopyrite veins, the homogenization temperatures of the brine inclusions are mainly below 300 °C, implying that the temperature range from 440 °C to 300 °C is the main copper mineralization interval. The precipitation temperature of chalcopyrite fits the fact that the copper ore-body is present within the potassic and early phyllic alteration zones.Hematite and magnetite are common within high-salinity inclusions in all vein types, indicating the high oxidation property of the ore-forming fluid. High oxidation facilitates the scavenging of sulfur and chalcophile metals into magmatic–hydrothermal systems. Moreover, hematite or magnetite deposition can facilitate the reduction of sulfate to sulfide and decrease pH values, ultimately affecting sulfide precipitation and hydrothermal alteration. The constant high oxidation is crucial for the metallogenesis of the Naruo porphyry Cu-Au deposit.

Faradaic Processes at the Interaction of Low-Temperature Plasma with Water and Aqueous Solutions

The paper considers the mechanism of reactions that lead to a change in the physicochemical properties of water in the case of its electrochemical activation with non-equilibrium plasma. The uniqueness of the method of the low-temperature plasma electrolysis (LTPE) consists in the fact that one electrode is placed in the liquid phase while the other is placed at some distance from the surface of the liquid, which offers new possibilities for the electrochemical method. It is shown that in the LTPE treatment of water, some destructive changes occur, which can result in the formation of peroxide and superoxide compounds with high oxidation properties. It is supposed that the mechanism of these processes is based on the appearance and functioning of a bipolar electrode at the liquid–gas interface.

Degradation kinetic study of cholesterol lowering statin drug using sono-hybrid techniques initiated by metal-free polymeric catalyst

Abstract The present study addressed the degradation kinetics of cholesterol lowering statin drug using metal-free polymeric catalyst g-C3N4 synthesized through sonochemical method followed by thermal condensation. The photocatalytic experiments were performed to assess the catalytic activity of the synthesized g-C3N4 catalyst. The results revealed that the g-C3N4 possesses high oxidation properties and able to degrade ∼93% of lovastatin within a short span of time 10 min under sono-hybrid technique with a rate constant of 15.1 × 10–2 min–1. On the other hand, the maximum synergy index was attained when the ultrasound was applied with g-C3N4 nanoparticles. A significant enhancement of 2.25 folds higher degradation efficiency was achieved as compared to the sonolysis process alone. This enhancement is due to the addition of catalyst which facilitates more nucleation sites for cavitation bubbles and promoted cavitation phenomenon in the system. The study of adsorption and oxidation processes revealed that the degradation of lovastatin was primarily by oxidation reaction. When the experiments were performed at low pH, a significant degradation was observed – which is due to the formation of hydronium ions (H3O+). This H3O+ produces alternative and reactive species such as •OH, •O, HO 2 • in the presence of free electrons in the reaction solution. The maximum synergy was seen for (US+g-C3N4) process followed by (US+g-C3N4+H2O2+UVC) and (US+UVC). The experimental results of stability and reusability of the catalyst also confirmed that the catalyst could be easily regenerated and reused for several times without losing any catalytic activity – which might be useful for reducing the total operating cost for a wastewater treatment plant.

Effect of hydrogen peroxide on photoelectric properties of high-transmittance FTO films prepared by spray pyrolysis

The FTO film prepared by spray pyrolysis has low efficiency and most of the precursors are discharged in the form of waste steam. According to the high oxidation property of H2O2, it is attempted to improve the film formation rate by changing the concentration of H2O2. Fluorine-doped SnO2 (FTO) thin films with high transmittance were prepared by spray pyrolysis using monobutyltin trichloride as the tin source and ammonium fluoride as the fluorine source. Different concentrations of hydrogen peroxide (0–0.08 M) are added to the precursor solution. In this paper, we studied the effect of hydrogen peroxide on the structure, surface morphology and photoelectric properties of FTO thin films. The results show that the growth rate of the FTO films increased from 6.04 nm/s to 8.36 nm/s with the increase of H2O2 concentration from 0 to 0.08 M. The optimum preparation process is H2O2 concentration controlled at 0.04 M, and FTO thin films suitable for solar cells are prepared. It has excellent performance parameters; carrier concentration:2.74 ∗ 1021 cm−3; carrier mobility:55.92 cm2 V−1 s−1; photoelectric quality factor:2.66 × 10−3·Ω−1and the average transmittance of visible light: 79.87%. At the same time, increasing H2O2 concentration leads to narrowing of optical band gap. Adding appropriate hydrogen peroxide concentration can improve the film production rate and obtain excellent quality films.

Green fabrication of bentonite/chitosan@cobalt oxide composite (BE/CH@Co) of enhanced adsorption and advanced oxidation removal of Congo red dye and Cr (VI) from water

Bentonite/chitosan composite supported by green fabricated Co3O4 was successfully synthesized and its physicochemical properties were investigated utilizing several analytic techniques. The formation of the composite was confirmed by the XRD patterns, SEM, HRTEM images, and FT-IR analysis. The adsorption properties of bentonite/chitosan@Co3O4 for acidic dye (Congo red) and Cr(VI) ions were investigated. The kinetic studies reflected the saturation of the composite surface after 480 min for both Congo red molecules and Cr(VI) ions. Additionally, the systems are of chemisorption nature and showed excellent fitting with Pseudo-second order model. The mathematical parameters of the isotherm models revealed a monolayer uptake of Congo red molecules and Cr(VI) ions and represented mainly by the Langmuir model. The theoretical calculated maximum adsorption capacity (qmax) is 303 mg/g and 250 mg/g for Congo red molecules and Cr(VI) metal ions, respectively. The composite is of high reusability and can be used effectively for six runs of decontamination of Congo red molecules and Cr(VI) ions. Moreover, it is of high oxidation properties and can be used in the photocatalytic reduction of Congo red molecules and Cr(VI) ions from water. Besides that, bentonite/chitosan@Co3O4 green composite was used in purification of realistic water samples which make it one of the promising adsorbents.