High-resolution X-ray Photoelectron Spectroscopy Research Articles

Green synthesis of N-doped MWCNTs via simple modification of CVD technique and evaluation of its viability as an electrode in AEMFC

The conventional synthesis of multi-walled carbon nanotubes (MWCNT) presents an environmental challenge due to toxic precursors. This research proposes a green synthesis of MWCNT by chemical vapor deposition (CVD) using a natural carbon source precursor (olive oil). Nitrogen gas was used as an inert atmosphere and a carrier for the evaporator precursor (200 °C). MWCNTs were synthesized at 900 °C using NiCl2 as a catalyst. MWCNTs had two treatments: functionalized and purified with HNO3 and HCl. Different physicochemical techniques characterized the MWCNT, such as X-ray diffraction (XRD), FTIR, high-resolution transmission electron microscopy (HRTEM), XPS, Raman spectroscopy, and CHN-S. The size of the MWCNT grew to be between de 15 a 25 nm with a purity of 20%, while the Raman spectroscopy revealed structural changes in the MWCNT after the purification treatment due to variations in the ID/IG index. All the synthesized MWCNTs were electrochemically characterized with linear sweep and cyclical voltammetry to analyze their electrocatalytic response to oxygen reduction reaction (ORR) in alkaline media.

Plasmonic nanoparticles doped metal oxide hybrid materials for efficient photocatalytic dye degradation and strong anti-biofilm activity

Plasmonic silver nanoparticles (AgNPs) doped ZnO (Ag-ZnO) nanoplates were synthesized by simple wet chemical method in presence of hexylamine with an intent to improve the visible light mediated photocatalytic activity of ZnO. Powder X-ray diffraction (PXRD) analysis confirmed the integration of AgNPs with ZnO nanoplates. High-resolution transmission electron microscopic (HR-TEM) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the formation of ZnO nanoplates and AgNPs doping. The concentration of Ag in ZnO nanoplates was increased by increasing hexylamine concentration. Ag-ZnO hybrid nanoplates exhibited efficient degradation of organic dyes (methyl orange (MO), methylene blue (MB), Eosin Y (EY) and rhodamine B (RB)) in presence of sun light compared to the pristine ZnO. Further, AgNPs doping with ZnO strongly enhanced anti-biofilm activity and showed strong prevention of colonization. The increase of AgNPs concentration in ZnO nanoplates exhibited enhancement of both photocatalytic and anti-biofilm activity that might be attributed to the improved light absorption in the visible region.

Chemistry, structure, and thermodynamic stabilization of SiOC polymer derived ceramics made from commercial precursors

This study explores the energetics and structure of polymer derived ceramics (PDCs) derived from the pyrolysis of preceramic polymers: SPR-212 (SPR), polyhydromethylsiloxane (PHMS) blend, and 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (TTCS) at 1200 and 1500 °C. There are close similarities in the composition of PDCs derived from PHMS (blend) and SPR-212 at 1200 °C, but high-resolution X-ray photoelectron spectroscopy shows notable differences in their microstructure. Enthalpies of formation (ΔH°f,elem) of SPR-1200, TTCS-1200, PHMS-1200, SPR-1500, TTCS-1500, and PHMS-1500 are -154.40 ± 3.19, -116.35 ± 3.48, -197.55 ± 3.05, -170.12 ± 3.50, -167.29 ± 3.35, and -212.43 ± 2.71 kJ mol-1, respectively. PDCs derived from low-cost commercial precursors (PHMS blend) appear to be more thermodynamically stable than those derived from an industrial preceramic polymer (SPR-212). Thermodynamic stability of the SiOCs increases with pyrolysis temperature. The results suggest that differences in silicon mixed bonding environments and their relative amounts (SiO3C, SiO2C2, or SiOC3) lead to differences in thermodynamic stabilization.

Assessment of Cr doping on TiO2 thin films deposited by a wet chemical method

Undoped and Cr-doped TiO2 thin films were synthesized by the dip-coating sol-gel process with titanium isopropoxide and chromium (III) chloride hexahydrate being used as the precursors. The chromium concentrations changed for different molar ratios, namely, 2, 4, and 8 wt.%. The samples, coated on glass substrates, were later annealed in air at 450 °C for 60 min. The influence of Cr doping on the structural, surface chemical, and optical properties of the samples was studied by several techniques, including EDS, Raman, UV–Vis, RT-PL, and XPS spectroscopies, as well as SEM and XRD. The diffraction patterns indicated that all the films displayed the anatase structure with the crystallite size decreasing with chromium doping. The same structure was confirmed by Raman spectroscopy measurements. UV–Vis absorption spectra of the samples showed a red shift of the fundamental absorption edge in the visible range following the increase of Cr doping concentration. In addition, the RT-PL study revealed that the dopant incorporation causes a decrease in the PL intensity. The EDS analysis revealed the presence of Ti, O, and Cr in the materials. Moreover, from high-resolution XPS Ti 2p spectra, titanium was found to be in the Ti4+ oxidation state evidencing the formation of TiO2, while the Cr 2p fitting analysis showed that chromium is present in the Cr (III) and Cr-metal states.

Sodium Alginate-CuS Nanostructures Synthesized at the Gel-Liquid Interface: An Efficient Photocatalyst for Redox Reaction and Water Remediation.

The use of visible light to propel chemical reactions is an exciting area of study that is crucial in the current socioeconomic environment. However, various photocatalysts have been developed to harness visible light, which consume high energy during synthesis. Thus, synthesizing photocatalysts at gel-liquid interfaces in ambient conditions is of scientific importance. Herein, we report an environmentally benign sodium alginate gel being used as a biopolymer template to synthesize copper sulfide (CuS) nanostructures at the gel-liquid interface. The driving force for the synthesis of CuS nanostructures is varied by changing the pH of the reaction medium (i.e., pH 7.4, 10, and 13) to tailor the morphology of CuS nanostructures. The CuS nanoflakes obtained at pH 7.4 transform into nanocubes when the pH is raised to 10, and the nanostructures deform at the pH of 13. Fourier transform infrared spectroscopy (FTIR) confirms all the characteristic stretching of sodium alginate, whereas the CuS nanostructures are crystallized in a hexagonal crystal system, as revealed by the powder X-ray diffraction analysis. The high-resolution X-ray photoelectron spectroscopy (XPS) spectra show the +2 and -2 oxidation states of copper (Cu) and sulfur (S) ions, respectively. The CuS nanoflakes physisorbed a higher concentration of greenhouse CO2 gas. Owing to a lower band gap of CuS nanoflakes synthesized at a pH of 7.4, compared to other CuS nanostructures prepared at pH 10 and 13, CuS photocatalytically degrades 95% of crystal violet and 98% of methylene blue aqueous dye solutions in 60 and 90 min, respectively, under blue light illumination. Additionally, sodium alginate-copper sulfide (SA-CuS) nanostructures synthesized at a pH of 7.4 demonstrate excellent performance in photoredox reactions to convert ferricyanide to ferrocyanide. The current research opens the door to developing new photocatalytic pathways for a wide range of photochemical reactions involving nanoparticle-impregnated alginate composites prepared on gel interfaces.

Highly luminescent graphene core N-doped carbon nanodots prepared under spatial nanoconfinement

Nitrogen-dopped carbon nanodots (CNDs) with an extremely high quantum yield of photoluminescence (up to 95%) have been obtained by thermal treatment of citric acid embedded in the porous structure of silica with immobilized N-[3-(Trimethoxysilyl)propyl]ethylenediamine. Spatial isolation of molecular precursors in nanoreactors permits the preparation of high-quality nanoparticles with spheroidal geometry and size 2–5 nm. The particles obtained at 110–180 °C for 60–600 min demonstrate excitation-independent photoluminescence at 453 nm. HRTEM reveals that the CNDs demonstrate ordered crystalline structures of graphic materials, indicating the catalytic effect of the nanoreactor. The high-resolution XPS experiment proves the N-doping of CNDs with 4.0 at.% of nitrogen atoms incorporated into the graphene core as pyrrolic and ternary fragments.

Porous Carbon Aerogel Decorated with TiO2 Quantum Dots for Highly Improved Photocatalytic H2 Evolution

The design of photocatalysts plays a central role in determining the photocatalytic H2 yield. Here, we used a design strategy that is different from conventional methods to prepare our photocatalytic systems. Large porous carbon aerogels (CA) with rich surface areas were used to receive photogenerated electrons. TiO2 quantum dots were used as photocatalysts and anchored on large porous CAs to form CA@TiO2 systems. The H2 yield of the optimized CA@TiO2 composite is ∼2.1 mmol/g, ∼11 times higher than that of pure TiO2 quantum dots. High-resolution X-ray photoelectron spectroscopy and high-angle annular dark-field scanning transmission electron microscopy demonstrate that the photogenerated electrons can be easily transferred from TiO2 quantum dots to porous CAs. Thus, efficient charge separation can be realized for the succeeding highly efficient H2 evolution. Our results here provide a different way from conventional methods to design photocatalytic systems with high H2 yield.

Room-Temperature Ferromagnetism in Layered Mn-Substituted MoS2

Intrinsically two-dimensional (2D) ferromagnetic materials normally exhibit a low transition temperature, above which they would lose their magnetic properties. This makes it difficult to develop them for practical applications. Substituting transition metal atoms into 2D systems provides a straightforward way for achieving room-temperature ferromagnetism. Here, we propose a one-step chemical vapor deposition method to prepare Mn-substituted MoS2 monolayers, which exhibit robust magnetism, as confirmed by a combined study of physical property measurement systems and magneto-optical measurements. High-resolution transmission electron microscopy, Raman signals, and X-ray photoelectron spectroscopy analysis have all shown that the manganese atoms in MoS2 act as a substitute for the molybdenum sites. The microscopic origin of magnetism in Mn-MoS2 is further revealed on the basis of first-principles calculations, which corroborate the experimental results obtained. Our study demonstrates a simple route to creating 2D ferroelectric materials with broad prospects in spintronic devices and next-generation memory components.

Properties and antimicrobial activity of wheat-straw nanocellulose-arabinoxylan acetate composite films incorporated with silver nanoparticles

In the current study, the novel eco-friendly and biodegradable nanocomposite films (NC-AXAc) were prepared from wheat-straw NC and AXAc with improved functional properties. NC derived from wheat-straw cellulose has a fibre-like structure with mean-particle size in the 340–520 nm range. AX derived AXAc was prepared with Degree of Substitution (DS) in the range of 1.85–1.89. Furthermore, to enhance antimicrobial properties, AgNPs were prepared via the reduction method using NaBH4 and added into the concentration of 4 × 10−4M into the emulsion forming composite films. The silver nanoparticles (AgNPs) incorporated in the composite exhibited an average size of 40–70 nm and a surface plasmon resonance (SPR) absorption peak at 395 nm. The high-resolution XPS spectrum of the Ag element showed that the two peaks at around 374.2 eV (Ag3d3/2) and 368.2 eV (Ag3d5/2) clearly revealed the metallic Ag existence in composite films. SEM analysis revealed the coarse and heterogeneous morphology of AgNPs incorporated films. The AgNPs incorporated composites exhibited good mechanical, thermal stability, and antimicrobial activity. The results suggested that AgNPs incorporated NC-AXAc composites could be used as a potential biodegradable antimicrobial nanocomposite in active food packaging systems for shelf-life extension of perishable commodities.

Synergistic coupling {101}-{111} facet of N-doped TiO2 film enhance spatial charge separation for methylene blue photodegradation

The synthesis of N-doped TiO2 film with co-exposed {101} and {111} facets via a one-pot facile hydrothermal method had proven to enhance the photocatalytic activity of TiO2. The high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS) data show the incorporation of N ions into the TiO2 accomplishes the facet modification. The shifting of the N-doped TiO2 photocatalyst adsorption bandgap toward a higher wavelength was identified as the TiO2 band gap was reduced. Up to 66 % methylene blue had successfully been degraded with the aid of N-doped TiO2 as an active photocatalyst. The enhanced photodegradation of N-doped TiO2 film is mainly attributed to the presence of {101} and {111} facets, leading to the efficient separation of carriers and lengthening the life of photogenerated carriers, consequently improving its photocatalysis potential.

Unveiling the parasitic-reaction-driven surface reconstruction in Ni-rich cathode and the electrochemical role of Li2CO3

Nickel-rich transition-metal oxides are widely regarded as promising cathode materials for high-energy-density lithium-ion batteries for emerging electric vehicles. However, achieving high energy density in Ni-rich cathodes is accompanied by substantial safety and cycle-life obstacles. The major issues of Ni-rich cathodes at high working potentials are originated from the unstable cathode-electrolyte interface, while the underlying mechanism of parasitic reactions towards surface reconstructions of cathode materials is not well understood. In this work, we controlled the Li2CO3 impurity content on LiNi0.83Mn0.1Co0.07O2 cathodes using air, tank-air, and O2 synthesis environments. Home-built high-precision leakage current and on-line electrochemical mass spectroscopy experiments verify that Li2CO3 impurity is a significant promoter of parasitic reactions on Ni-rich cathodes. The rate of parasitic reactions is strongly correlated to Li2CO3 content and severe performance deterioration of Ni83 cathodes. The post-mortem characterizations via high-resolution transition electron microscope and X-ray photoelectron spectroscopy depth profiles reveal that parasitic reactions promote more Ni reduction and O deficiency and even rock-salt phase transformation at the surface of cathode materials. Our observation suggests that surface reconstructions have a strong affiliation to parasitic reactions that create chemically acidic environment to etch away the lattice oxygen and offer the electrical charge to reduce the valence state of transition metal. Thus, this study advances our understanding on surface reconstructions of Ni-rich cathodes and prepares us for searching for rational strategies.

Two-Dimensional Self-Assembly Driven by Intermolecular Hydrogen Bonding in Benzodi-7-azaindole Molecules on Au(111).

The control of molecular structures at the nanoscale plays a critical role in the development of materials and applications. The adsorption of a polyheteroaromatic molecule with hydrogen bond donor and acceptor sites integrated in the conjugated structure itself, namely, benzodi-7-azaindole (BDAI), has been studied on Au(111). Intermolecular hydrogen bonding determines the formation of highly organized linear structures where surface chirality, resulting from the 2D confinement of the centrosymmetric molecules, is observed. Moreover, the structural features of the BDAI molecule lead to the formation of two differentiated arrangements with extended brick-wall and herringbone packing. A comprehensive experimental study that combines scanning tunneling microscopy, high-resolution X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and density functional theory theoretical calculations has been performed to fully characterize the 2D hydrogen-bonded domains and the on-surface thermal stability of the physisorbed material.

Thermally Ultrarobust S = 1/2 Tetrazolinyl Radicals: Synthesis, Electronic Structure, Magnetism, and Nanoneedle Assemblies on Silicon Surface.

Open-shell organic molecules, including S = 1/2 radicals, may provide enhanced properties for several emerging technologies; however, relatively few synthesized to date possess robust thermal stability and processability. We report the synthesis of S = 1/2 biphenylene-fused tetrazolinyl radicals 1 and 2. Both radicals possess near-perfect planar structures based on their X-ray structures and density-functional theory (DFT) computations. Radical 1 possesses outstanding thermal stability as indicated by the onset of decomposition at 269 °C, based on thermogravimetric analysis (TGA) data. Both radicals possess very low oxidation potentials <0 V (vs. SCE) and their electrochemical energy gaps, Ecell ≈ 0.9 eV, are rather low. Magnetic properties of polycrystalline 1 are characterized by superconducting quantum interference device (SQUID) magnetometry revealing a one-dimensional S = 1/2 antiferromagnetic Heisenberg chain with exchange coupling constant J'/k ≈ -22.0 K. Radical 1 in toluene glass possesses a long electron spin coherence time, Tm ≈ 7 μs in the 40-80 K temperature range, a property advantageous for potential applications as a molecular spin qubit. Radical 1 is evaporated under ultrahigh vacuum (UHV) forming assemblies of intact radicals on a silicon substrate, as confirmed by high-resolution X-ray photoelectron spectroscopy (XPS). Scanning electron microscope (SEM) images indicate that the radical molecules form nanoneedles on the substrate. The nanoneedles are stable for at least 64 hours under air as monitored by using X-ray photoelectron spectroscopy. Electron paramagnetic resonance (EPR) studies of the thicker assemblies, prepared by UHV evaporation, indicate radical decay according to first-order kinetics with a long half-life of 50 ± 4 days at ambient conditions.

Construction of 2D/2D Mesoporous WO3/CeO2 Laminated Heterojunctions for Optimized Photocatalytic Performance.

Photocatalytic elimination of antibiotics from the environment and drinking water is of great significance for human health. However, the efficiency of photoremoval of antibiotics such as tetracycline is severely limited by the prompt recombination of electron holes and slow charge migration efficacy. Fabrication of low-dimensional heterojunction composites is an efficient method for shortening charge carrier migration distance and enhancing charge transfer efficiency. Herein, 2D/2D mesoporous WO3/CeO2 laminated Z-scheme heterojunctions were successfully prepared using a two-step hydrothermal process. The mesoporous structure of the composites was proved by nitrogen sorption isotherms, in which sorption-desorption hysteresis was observed. The intimate contact and charge transfer mechanism between WO3 nanoplates and CeO2 nanosheets was investigated using high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy measurements, respectively. Photocatalytic tetracycline degradation efficiency was noticeably promoted by the formation of 2D/2D laminated heterojunctions. The improved photocatalytic activity could be attributed to the formation of Z-scheme laminated heterostructure and 2D morphology favoring spatial charge separation, confirmed by various characterizations. The optimized 5WO3/CeO2 (5 wt.% WO3) composites can degrade more than 99% of tetracycline in 80 min, achieving a peak TC photodegradation efficiency of 0.0482 min-1, which is approximately 3.4 times that of pristine CeO2. A Z-scheme mechanism is proposed for photocatalytic tetracycline by from WO3/CeO2 Z-scheme laminated heterojunctions based on the experimental results.

Synthesis and catalytic performance of nanoflower-like Ru@CoAl-LDH composite catalyst for NaBH4 hydrolysis

Sodium borohydride (NaBH4) has been widely regarded as the one of most promising future hydrogen (H2)-generated materials. Therefore, it is necessary to find a catalyst with higher catalytic performance to promote the on-demand H2 release of NaBH4 hydrolysis. In this study, a [email protected] catalyst was developed by immobilizing Ru nanoparticles (Ru NPs) on the surface of Co Al Layered Double Hydroxide (CoAl-LDH) nanocurds. The Ru NPs were prepared by H2 reduction, and nanoflower-like CoAl-LDH was synthesized through a one-step solvothermal method. The microstructure and composition of the catalysts were investigated through scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results showed that [email protected] exhibited good catalytic performance toward the NaBH4 hydrolysis. At 30 °C, the hydrogen generation rate of the hydrolysis reaction was 44.34 L·min−1·gRu−1, and the reaction activation energy was 38.83 kJ·mol−1, and superior to many catalysts of the same type. Because of its high activity, low activation energy and excellent economic performance, this catalyst has high potential for applications in NaBH4 hydrolysis.

Construction of tight ultrafiltration membrane for efficient dye/salt separation with physical and chemical self-healing property

This work developed a novel self-healing tight UF membrane based on damages to membrane during operation and cleaning via blending AMPS-PANI into the membrane matrix, which can not only endow the membrane with physical and chemical self-healing properties, but also enable the membrane to obtain effective separation performance of inorganic salt and dyes. Taking AMPS-PANI membrane (M4) as an example, the self-healing test showed that the dye/salt rejection rates of M4 membrane recovered to near pre-damage levels (more than 98%) for the physical damage. As for chemical damage, the high-resolution XPS spectra of S 2p of M4 membrane after damage displayed a larger S-C-C peak area than that before damage. The above results prove that the membrane has self-healing ability after physical and chemical damage. The observed physical self-healing property is ascribed to the swelling behavior of AMPS hydrogels, the fluidity of hydrogel chains and strong hydrogen bonding, and owing the chemical self-healing property to the Michael addition reaction between carbon–carbon double bonds and free radicals. The pure water flux, dye/salt rejection rate, structure, mechanical properties and porosity of the self-healing tight UF membrane were systematically investigated to evaluate its feasibility as an actual filtration membrane for textile wastewater. The results of the research indicate that membrane including both physical and chemical self-healing is a promising way to improve water filtration membrane with self-healing ability.

Irradiation-enhanced Interactions at UO2/Al2O3/Al Interfaces

Combustion synthesis is used to prepare thin UO2 films on aluminum alloy substrates. This simple preparation method involves electrospraying uranyl nitrate + acetylacetone + 2-methoxyethanol solution on the substrate, followed by a short annealing at 350 or 550 °C. The irradiation of films with a 40Ar2+ ion beam (energy of 1.7 MeV and fluences of 7.7 × 1016 and 1.3 × 1017 ions/cm2) is conducted to investigate irradiation-induced restructuring processes. High-resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) investigations show that the annealing temperature significantly influences the crystallinity and stability of materials during irradiation. A small amount of Mg in the alloy substrate diffuses into the amorphous Al2O3 interfacial layer between the film and the substrate. Local thermal spikes from the incoming ions facilitate the irradiation-induced mixing of immiscible Al2O3 and UO2 for the materials prepared at 350 °C. This mass diffusion produces relatively large cavities at the interface. Selective diffusion of a more significant amount of Mg for the materials prepared at 550 °C suppresses the mixing of the Al2O3 interlayer with the film but forms MgyU1–yO2±x solid solutions during irradiation. Local thermal heating triggers the precipitation of a discontinuous crystalline MgO layer close to the film surface. The enhanced and selective diffusion of Mg into the film makes the materials prepared at 550 °C more robust and mechanically stable than those prepared at 350 °C.

α-In2Se3 Nanostructure-Based Photodetectors for Tunable and Broadband Response

The strong thickness-dependent narrow direct band gap of few-layer α-In2Se3 makes it a promising candidate for high-performance photodetectors. However, few researchers focus on the relationship between thickness and optoelectronic characteristics, and most results are based on the mechanically exfoliated α-In2Se3 nanoflakes. Herein, a reliable physical vapor deposition strategy to grow α-In2Se3 nanosheets with tunable thickness and submillimeter scale is reported. High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) studies confirmed the high-quality growth of α-In2Se3 nanosheets. The back-gate field-effect transistors on SiO2 substrates display n-type semiconductor behavior. A systematical investigation of the optoelectronic properties reveals a thickness-dependent broadband response from visible (447 nm) to near-infrared (1550 nm) wavelengths with better and excellent performance obtained in thicker α-In2Se3 nanosheets than that in thinner devices. More importantly, a great improvement of the responsivity, detectivity, and external quantum efficiency (EQE) can be achieved by changing the thickness of In2Se3. The photodetector exhibits an outstanding photoresponsivity of 347.6 A/W, an ultrahigh detectivity of 1.5 × 1013 Jones, and an external quantum efficiency of 8.3 × 104%, which is superior to several α-In2Se3 nanostructure- or other two-dimensional (2D)-based photodetectors. The thickness-dependent broadband response characteristics make the α-In2Se3 nanostructure a promising candidate for multifunctional optoelectronic device applications.

Nanoarchitecture of a Ti3C2@TiO2 Hybrid for Photocatalytic Antibiotic Degradation and Hydrogen Evolution: Stability, Kinetics, and Mechanistic Insights.

Designing of a visible-light-driven semiconductor-based heterojunction with suitable band alignment and well-defined interfacial contact is considered to be an effective strategy for the transformation of solar-to-chemical energy and environmental remediation. In this context, MXenes have received tremendous attention in the research community due to their merits of abundant derivatives, elemental composition, excellent metallic conductivity, and surface termination groups. Meanwhile, a facile synthetic strategy for MXene-derived TiO2 nanocomposites with stable framework and higher photocatalytic activity under visible-light irradiation still remains a challenge for researchers. Herein, we report a novel synthetic strategy of preparing a two-dimensional Ti3C2@TiO2 nanohybrid by a facile reflux method under acidic conditions. In this oxidation reaction, protonation of the hydroxyl terminal group of MXene creates Ti more electrophilic and susceptible to an oxidative nucleophilic addition reaction with the presence of both water and oxygen. The physicochemical properties of the nanohybrid Ti3C2@TiO2 were verified by varieties of characterization techniques. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy analysis specifically elucidated the intimate interfacial interaction between Ti3C2 and TiO2. The optimized Ti3C2@TiO2-48 h photocatalyst exhibited the highest tetracycline hydrochloride (TCH, 90% in 90 min) degradation efficiency in comparison to pristine TiO2 with a rate constant (k) of 0.02463 min-1. The major contribution of •O2- and •OH radicals throughout photocatalytic TCH degradation was confirmed by the trapping experiment. Moreover, the photocatalyst showed the highest hydrogen generation rate of 140.8 μmol h-1 along with an apparent conversion efficiency of 2.2%. The excellent photocatalytic activity of Ti3C2@TiO2 originated from the superior electrical conductivity of cocatalyst Ti3C2, which facilitated spatial photogenerated e-/h+ separation and transfer at the Ti3C2 MXene@TiO2 interface. Overall, this research work will describe a promising protocol of designing MXene-derived photocatalysts toward efficient environmental remediation and wastewater treatment applications.

Trimetallic Oxide Foam as an Efficient Catalyst for Fixation of CO2 into Oxazolidinone: An Experimental and Theoretical Approach

The excess anthropogenic CO2 depletion via the catalytic approach to produce valuable chemicals is an industrially challenging, demanding, and encouraging strategy for CO2 fixation. Herein, we demonstrate a selective one-pot strategy for CO2 fixation into "oxazolidinone" by employing stable porous trimetallic oxide foam (PTOF) as a new catalyst. The PTOF catalyst was synthesized by a solution combustion method using transition metals Cu, Co, and Ni and systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), N2 sorption, temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS) analysis. Due to the distinctive synthesis method and unique combination of metal oxides and their percentage, the PTOF catalyst displayed highly interconnected porous channels along with uniformly distributed active sites on its surface. Well ahead, the PTOF catalyst was screened for the fixation of CO2 into oxazolidinone. The screened and optimized reaction parameters revealed that the PTOF catalyst showed highly efficient and selective activity with 100% conversion of aniline along with 96% selectivity and yield toward the oxazolidinone product at mild and solvent-free reaction conditions. The superiority of the catalytic performance could be due to the presence of surface active sites and acid-base cooperative synergistic properties of the mixed metal oxides. A doubly synergistic plausible reaction mechanism was proposed for the oxazolidinone synthesis experimentally with the support of DFT calculations along with bond lengths, bond angles, and binding energies. In addition, stepwise intermediate formations with the free energy profile were also proposed. Also, the PTOF catalyst displayed good tolerance toward substituted aromatic amines and terminal epoxides for the fixation of CO2 into oxazolidinones. Very interestingly, the PTOF catalyst could be significantly reused for up to 15 consecutive cycles with stable activity and retention in physicochemical properties.