Degree Of Oxidation Research Articles

Carbon Nanotube-Based Catalyst Modification to Improve Proton Exchange Membrane Fuel Cell Interlayer Interactions

Proton exchange membrane fuel cells (PEMFC) were identified as a highly viable solution for addressing climate-related issues. Previous theoretical investigations have underscored the significance of Pt nanoparticles as the optimal metal for hydrogen fuel cell catalysts due to their special activity and selectivity. [1] Current works focused on the utilisation, durability, and site activity of Pt particles on support, and most of the schemes achieved performance enhancement by loading Pt onto porous support with different morphology such as graphene, carbon fibre, and carbon black. [2] Some schemes have also incorporated cost considerations to achieve lower Pt loading. [3] However, the design of the catalyst layer (CL) structure in the membrane electrode assembly (MEA) must consider the interactions between the layers.Addressing the crucial aspects of water management, low contact resistance, and the establishment of effective three-phase boundary for MEA, multi-walled carbon nanotubes (MWCNTs) are a promising CL support due to their intrinsically high hydrophobicity, high axial electrical conductivity, and potential for ordered alignment. [4] However, the drawbacks of MWCNTs such as strong agglomeration, wall surface chemical inertness, and unopened ends are unfavourable for Pt nanoparticle loading, which is detrimental to MEA processing and leads to inhomogeneous CL surfaces. This further deteriorates the utilisation of Pt and increases the contact resistance. Previous efforts have explored methods such as introduction of polar functional groups on MWCNT using strong reflux oxidation condition, or nitrogen doping to construct localised pyridine structure. [5, 6] However, over-functionalisation can cause MWCNT to lose its favourable structure and properties.In this work, MWCNT was modified based on the operational requirements of the MEA from the viewpoint of interlayer interactions, including the search for the optimal degree of oxidation, N-doping, and micro-arrangement. MWCNT were functionalise by oxidising, N-doping, as well as micro-alignment to achieve lower contact resistance between CL and proton exchange membrane (PEM), better hydrophobicity, and enhanced performance. Furthermore, this work expects to construct a more continuously distributed three-phase boundary by aligning MWCNT to form a locally ordered structure, which is essential for the efficient utilisation of Pt active sites.Preliminary experiments in this work have tested a range of reflux oxidation conditions for MWCNT treated with concentrated nitric acid ranging from 0 to 10 h. The maximum power density of 979.81 mw cm-2 was achieved by Pt loading on 6h MWCNT oxidation time (Pt-MWCNT 6h). This represented a 59.53% improvement over the commercial Pt/C catalyst of 614.17 (mw cm-2) (Figure 1 (a)). In addition, due to the stronger electrical conductivity, the charge transfer resistance of Pt-MWCNT6h in the electrochemical impedance spectroscopy (EIS) test was 0.09 Ohm cm-2, which was 48.86% lower than that of Pt/C (Figure 1 (b)). This study will discuss the developed catalysts and their efficacy in a working fuel cell system.In conclusion, this research proposed alternative perspectives on the design of the CL based on the actual operational characteristics of MEA with emphasised on the interlayer interaction between CL and other layer. Additionally, the research will validate the impact of low-functionalization modification of MWCNTs on the performance of PEMFC, which simplifying the preparation challenges of CL and contributing for the widespread commercial application of PEMFCs on a larger scale. References Seh, Z.W., et al., Combining theory and experiment in electrocatalysis: Insights into materials design. Science, 2017. 355(6321): p. eaad4998.Sui, S., et al., A comprehensive review of Pt electrocatalysts for the oxygen reduction reaction: Nanostructure, activity, mechanism and carbon support in PEM fuel cells. Journal of Materials Chemistry A, 2017. 5(5): p. 1808-1825.Tian, Z.Q., et al., A Highly Order-Structured Membrane Electrode Assembly with Vertically Aligned Carbon Nanotubes for Ultra-Low Pt Loading PEM Fuel Cells. Advanced Energy Materials, 2011. 1(6): p. 1205-1214.Lehman, J.H., et al., Evaluating the characteristics of multiwall carbon nanotubes. Carbon, 2011. 49(8): p. 2581-2602.Hernández-Fernández, P., et al., Functionalization of multi-walled carbon nanotubes and application as supports for electrocatalysts in proton-exchange membrane fuel cell. Applied Catalysis B: Environmental, 2010. 99(1): p. 343-352.Gribov, E.N., et al., Effect of modification of multi-walled carbon nanotubes with nitrogen-containing polymers on the electrochemical performance of Pt/CNT catalysts in PEMFC. Materials for Renewable and Sustainable Energy, 2019. 8(1): p. 7. Figure 1

Electrocatalytic Conversion of CH4 to High Value-Added Liquid Fuel over Binary Metal Oxide Tandem Catalysts

As the main component (> 85%) of combustible ice and shale gas, methane (CH4), plays a significant role in the greenhouse effect.(1) Although CH4 was widely used to synthesize high value-added Cx oxygenates via indirect industrial reforming with high-energy consumption. The accurate control of oxidation degree in CH4 conversion remains a great challenge.(2) Therefore, it is difficult to achieve high conversion rate and high selectivity at the same time. The convenience and reliability of the control of reaction potential, as one of the advantages of electrocatalysis technology, can effectively address the above problems.(1, 3) Electrochemical technologies of CH4-to-Cx oxygenates are regarded as one of the most attractive pathways to produce bulk industrial liquid fuels.(4) Especially in the premise of clean energy as an energy source, the electrochemical conversion of methane demonstrates very advantageous market potential. In this work, we prepared a ZrO2 modified FeOx binary metal oxides tandem catalyst to accelerate partial oxidation of CH4 under ambient condition. With CO3 2- as an oxidant, ZrO2@FeOx tandem catalyst shows remarkable CH4 conversion performance with large current density gap (13.65 mA cm-2) and long-term electrochemical stability (negligible attenuation (8 %) after 48 hours) in three-electrodes cell. In addition, in a flow reactor, ZrO2@FeOx-based electrode also exhibits a highly stable operating lifespan over 72 hours at a large current density 50 mA cm-2 and achieve a feasible CH4-liqid fuel conversion with high total faradaic efficiency.References F. Liu, Y. Yan, G. Chen and D. Wang, Green Chemistry, 26, 655 (2024).S. Yuan, Y. Li, J. Peng, Y. M. Questell-Santiago, K. Akkiraju, L. Giordano, D. J. Zheng, S. Bagi, Y. Román-Leshkov and Y. Shao-Horn, Advanced Energy Materials, 10, 2002154 (2020).M. R. A. Kishore, S. Lee and J. S. Yoo, Adv Sci (Weinh), 10, e2301912 (2023).L. Fu, R. Zhang, J. Yang, J. Shi, H. Y. Jiang and J. Tang, Advanced Energy Materials, 13 (2023).

Impact of reduced-graphene-oxide functionalization of flower-like zinc-oxide nanostructures on sensing performance of resistive ethanol gas sensor

This research presents a sensitive resistive ethanol gas sensor based on reduced graphene oxide (rGO)-functionalized Zinc oxide nanoflowers (ZnO NFs). Upon completion of synthesis, the resulting nanostructures were cast onto the photolithographed silver interdigitated electrodes positioned on an Al2O3 substrate. The graphene oxide (GO) with a low oxidation degree was synthesized using a Hummer's method. In the pursuit of optimizing sensing performance, rGO-functionalized ZnO NFs were synthesized through a one-pot hydrothermal process, utilizing different initial quantities of GO (0 mg, 2 mg, 8 mg, and 12 mg). According to the gas sensing measurements, the fabricated sensor with 8 mg initial GO showed the highest response to ethanol at 250 °C. The results show that the GO addition reduced the optimal working temperature of the pure ZnO NFs from 350 °C to 250 °C. The sensor exhibited a good selectivity, repeatability, and high long-term stability. Enhanced ethanol sensing response of the optimized gas sensor was related to the formation of p-n heterojunction between p-type rGO (formed during hydrothermal process at 200 °C) and n-type ZnO and the presence of the optimal amount of rGO on the surface of NFs. The results obtained in this investigation stress the significance of pinpointing the optimal quantity of GO for producing rGO-ZnO nanoflowers with the highest possible sensitivity to ethanol gas.

Laser irradiation-induced surface-enhanced Raman scattering of Sn@SnO composite films

In this work, Sn@SnO composite films were obtained by Nd:YAG fiber pulsed laser ablation at room temperature. The effects of laser ablation on the microstructure, optical properties, and Raman scattering properties of the films were investigated. Tunable Localized Surface Plasmon resonance(LSPR)of Sn nanoparticles was realized in the wavelength range of 380–450 nm by varying the scanning rate to modulate the degree of oxidation of Sn nanoparticles. Surface enhanced Raman scattering (SERS) was also observed in the composite structure, which was demonstrated excellent stability and SERS sensitivity with the detectable concentration of methylene blue (MB) as low as 10−9 M and an enhancement factor of 1.75 × 105 as well as a good uniformity. Finally, the electric field distribution of the samples before and after the laser treatment is simulated by the finite difference in time domain (FDTD) method, and the results are consistent with those of experimental ones.

Antioxidant amyloid fibril derived from rice protein hydrolysate as stabilizer towards preparing high-stable emulsion

An antioxidant amyloid fibril was prepared as an emulsifier by fibrillating limited enzymatic hydrolysis-modified rice protein (HRP). The purpose of this study was to investigate the feasibility of using fibrillated HRP to stabilize oil-in-water emulsion. A free radical scavenging assay revealed that the antioxidant activity of fibrillated HRP was 2.09 times higher than that of native rice protein. Fibrillated HRP demonstrated a marked reduction in interfacial tension, increased surface hydrophobicity and contact angle (> 80°), and rapid adsorption to the interface, with 35.34 ± 2.43% interfacial adsorbed protein content. The fibrillated HRP barriers resisted environment stresses such as NaCl, pH variations, long-term storage, while reducing lipid oxidation degree. Additionally, fibrillated HRP-based emulsion was more effective in protecting β-carotene from degradation compared to other samples. These findings provide theoretical support for the development of rice protein-based antioxidant emulsifiers and modification of emulsifying properties of plant proteins.

Enhanced Dye Adsorption on Cold Plasma-Oxidized Multi-Walled Carbon Nanotubes: A Comparative Study.

The oxidation of multi-walled carbon nanotubes (MWCNTs) using cold plasma was investigated for their subsequent use as adsorbents for the removal of dyes from aqueous solutions. The properties of MWCNTs after plasma modification and their adsorption capacities were compared with pristine and chemically oxidized nanotubes. The modification process employed a reactor where plasma was generated through dielectric barrier discharges (DBD) powered by high-voltage nanosecond pulses. Various modification conditions were examined, such as processing time and pulse voltage amplitude. The degree of oxidation and the impact on the chemistry and structure of the nanotubes was investigated through various physicochemical and morphological characterization techniques (XPS, BET, TEM, etc.). Maximum oxidation (O/C = 0.09 from O/C = 0.02 for pristine MWCNTs) was achieved after 60 min of nanopulsed-DBD plasma treatment. Subsequently, the modified nanotubes were used as adsorbents for the removal of the dye methylene blue (MB) from water. The adsorption experiments examined the effects of contact time between the adsorbent and MB, as well as the initial dye concentration in water. The plasma-modified nanotubes exhibited high MB removal efficiency, with adsorption capacity proportional to the degree of oxidation. Notably, their adsorption capacity significantly increased compared to both pristine and chemically oxidized MWCNTs (~54% and ~9%, respectively). Finally, the kinetics and mechanism of the adsorption process were studied, with experimental data fitting well to the pseudo-second-order kinetic model and the Langmuir isotherm model. This study underscores the potential of plasma technology as a low-cost and environmentally friendly approach for material modification and water purification.

Evolution of macromolecular structure during coal oxidation via FTIR, XRD and Raman

The analysis of the macromolecular structure and morphology in coal during oxidation is the basis to explore the mechanism of spontaneous combustion. To explore the evolutionary rules of coal macromolecular structure during oxidation, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Raman Spectroscopy (Raman) were employed to analyze the coal samples with different oxidation degrees. The results revealed that the oxidation action led to the decrease of the aliphatic structures and aromatic hydroxyl groups in coal, while promoting the formation of oxygen-containing functional groups and aromatic structures. It also led to a relative increase of free hydroxyl groups linked to hydrogen bonds. The aromatic layer spacing (d002) decreased with increasing oxidation degree, while the microcrystal stacking height (Lc), the aromatic layer diameter (La), the average number of crystal stacking layers (n) generally increased. It indicated that small aromatic ring molecules in coal could undergo continuous polymerization during oxidation to form a single aromatic layer structure. The variation of Raman spectrum parameters exhibited a consistent decreasing trend in WD/WG, ID/IG, AD/AG, and A(GR+SL)/AG value, indicating an increase in the vibration of sp2 hybridization carbon atoms within the lattice structure of coal. Conversely, PG-D, AS/AD and A(GR+VL+VR)/AD value increased overall, suggesting that small aromatic rings decreased in content during oxidation while polymerizing into larger aromatic rings. The coal structure underwent a brief stage of disordered evolution during oxidation, followed by removal of impurity structures and condensation of aromatic structures due to increasing oxidation temperatures, ultimately leading to a highly ordered crystalline state. The oxidation process significantly influenced the development of coal's aromatic structure, particularly in less metamorphic coal. The research findings provide a theoretical basis for analyzing the underlying mechanism behind spontaneous combustion induced by coal oxidation.

One-step synthesis of g-C3N4/TiVCTx MXene electrodes for lithium-ion batteries and supercapacitors

The wide-ranging application of lithium-ion batteries (LIBs) is currently restricted by their slow ion dynamics and low capacity, which hinders the development of innovative electrode materials. Herein, the graphitic carbon nitride (g-C3N4)/TiVCTx composite was fabricated through in situ pyrolysis of urea to generate g-C3N4 nanosheets on the surface of TiVCTx nanosheets. The as-prepared g-C3N4 protective layer can reduce the degree of oxidation of TiVCTx MXene, restrain the re-stacking of TiVCTx nanosheets and minimize the risk of undesirable side reactions. As expected, the g-C3N4/TiVCTx electrode exhibits remarkable specific capacity of 1025.3 mAh/g after 150 cycles at 0.1 A/g and 558.3 mAh/g after 1000 cycles at 1.0 A/g for LIBs and a high specific capacitance of 508.9F g−1 in 0.5 M Na2SO4 electrolyte at 1.0 A/g after 7000 cycles for supercapacitors (SCs). Furthermore, the assembled g-C3N4/TiVCTx-30//LiFePO4 full cell presents stable specific capacity of 505.5 mAh/g at 0.1 A/g after 100 cycles and 255.2 mAh/g at 0.1 A/g along with a Coulombic efficiency of 97.9 % after 50 cycles at − 20 °C, demonstrating excellent low temperature tolerance. Density functional theory (DFT) calculation results indicated that the g-C3N4/TiVCTx-30 exhibits strongest adsorption capacity for Li+ with an adsorption energy of −3.85 eV. The introduction of g-C3N4 improves the insertion and extraction kinetics of Li+, effectively reducing the diffusion barrier. Consequently, the g-C3N4/TiVCTx-30 electrode exhibits potential application prospects in high-performance electrochemical energy storage devices. Our work provides valuable insights and significant research implications for improving the specific capacity and stability of TiVCTx MXene in the field of energy storage.

Study of inclusions-removal and slag-metal dispersion phenomenon in gas-stirred ladle

Abstract The slag-metal interface serves as a crucial locus for both chemical reactions and the adsorption of inclusions during secondary refining. This study first comprehensively reviews the methods of inclusions removal and then establishes a cold-state experiment using a water-oil system to reappear the phenomenon of slag-metal dispersion and inclusion adsorption. The distribution of slag droplets under varying slag volumes is analyzed in terms of the effect of bottom blow rates. Simultaneously, the volumetric fraction of oxygen on the slag-eye surface is analyzed. The result proved that the increase in oil layer thickness or the gas flow rate increase the volume of entrained oil. The dimensionless depth of entrained droplets was positively associated with gas flow rate or oil thickness. The dimensionless depth of “large droplets” and “small droplets” was in the range of 0–25 % and 0–60 %, respectively. Moreover, analysis of the gas composition above the slag-eye in a water-oil system is used to determine the degree of secondary oxidation. The oxygen volume fraction over the surface of the slag-eye decreases with the increase of gas flow rate. The oxygen volume fraction over the surface of the slag-eye is 1.51 % when the gas flow rate is 9 L/min.

Oxidation mechanism and microstructure evolution of invar alloy with high temperature annealing process

The high temperature oxidation behavior of Fe–36Ni Invar alloy in the forged billet stage and hot rolled rod stage in the compressed air atmosphere has been systematically studied. The results show that the oxide layer can be divided into the external oxide layer composed of Fe2O3, Fe3O4 and NiO, and the inner transition oxide layer composed of FeO, Fe2O3, Fe3O4 and NiO. In addition, hot rolled rod samples treated by solution and rolling have higher oxidation resistance. The mechanism of O diffusion during oxidation is analyzed, and it is found that the O atom adsorbed on the surface of the substrate diffuses into the grain along the grain boundary. The grain boundary is the optimal path for O diffusion to the interior of the material, which results in the degree of intergranular oxidation of the alloy being greater than the degree of intragranular oxidation. In summary, the oxidation resistance of Invar alloy can be improved by proper solution treatment and avoiding the formation of grain boundary cracks during production.

Effective removal of chromium, copper, and nickel heavy metal ions from industrial electroplating wastewater by in situ oxidative adsorption using sodium hypochlorite as oxidant and sodium trititanate nanorod as adsorbent

Sodium hypochlorite and synthesized sodium trititanate nanorods (Na2Ti3O7, 186 × 1270 nm) were used as the oxidant and adsorbents for in situ oxidative adsorption treatment of actual electroplating wastewaters containing Cr(VI) (2.6‒5.2 mg∙L‒1), Cu2+ (2.7‒5.4 mg∙L‒1), and Ni2+ (0.2705‒0.541 mg∙L‒1) ions at pH of 8.8‒9.1 and 20‒60 °C. The as-synthesized sodium trititanate nanorods were characterized by XRD, HRTEM, N2 adsorption/desorption, SEM, EDX, and Zeta potential techniques. The concentrations of heavy metal ions in wastewaters were analyzed by ICP technique. After in situ oxidative adsorption treatment under the concentrations of 25 g∙L‒1 for sodium hypochlorite and 125 mg∙L‒1 for sodium trititanate nanorods at 60 °C for 5 h, the heavy metal ion concentrations could be reduced from initial value of 2.6 to final value of 1.92 mg∙L‒1 for Cr(VI), 3.6 to 0.17 mg∙L‒1 for Cu2+, and from 0.2705 to 0.097 mg∙L‒1 for Ni2+, respectively. Cr(VI), Cu2+, and Ni2+ ions could be effectively removed by the in situ oxidative adsorption method. The in situ oxidative adsorption processes of Cr(VI), Cu2+, and Ni2+ ions are satisfactorily simulated by the pseudo-second order adsorption kinetics and Langmuir adsorption isotherm, respectively. Adsorption thermodynamics analyses reveal that the oxidative adsorption processes of Cr(VI), Cu2+, and Ni2+ ions are spontaneous and endothermic. The oxidation degree of metal-contained complexes influences the values of thermodynamics functions.

Photocatalytic performance of TiO2 modified with graphene derivatives and Fe (Ⅲ) at different thermal reduction temperatures

ABSTRACT To further investigate the synergistic effects of Fe (Ⅲ) and graphene derivatives with varying degrees of oxidation for photocatalysis, commercial titanium dioxide nanoparticles and graphene oxide were employed as precursors to synthesize the catalyst in this study. Graphene oxygenated derivatives and Fe (Ⅲ)-modified titanium dioxide photocatalysts with different oxidation degrees were prepared using a simple one-step solvothermal method. The results demonstrated that the photocatalytic performance in degrading rhodamine B and sulfamethoxazole was enhanced with an increase in the oxidation degrees of graphene materials. Through the combined action of delocalized conjugated π electrons as electron transfer mediators, Fe (Ⅲ) as an electron trap, and photosensitization reactions, titanium dioxide exhibited exceptional photocatalytic properties with the assistance of graphene derivatives and Fe (Ⅲ) co-catalysts in the degradation of organic compounds.

Fluorine atoms incorporation strengthens the strong metal-support interaction of PtNi@NFGC for enhanced methanol oxidation reaction performance under alkaline media

The regulatory mechanism of strong metal-support interaction (SMSI) is of great significance in improving the electrocatalytic performance for supported electrocatalysts. Here, PtNi alloy nanoparticles were deposited on N, F-codoped graphene-like carbon nanosheets (PtNi@NFGC) to construct a highly active interface for efficient methanol oxidation reaction (MOR), which solves the problems of high cost, poor activity and easy aggregation of Pt-based catalysts. Due to the high electrophilicity, F atoms doping into the carbon lattice can not only manipulate the electron structure and the state of the carbon skeleton, but also further trigger the stronger charge transfer between metal atoms and carbon support. Compared with single-doped PtNi@NGC, N, F-codoped PtNi@NFGC possesses a lower onset potential and methanol oxidation potential, higher methanol oxidation current and stronger CO tolerance. The results of the partial density of state (PDOS) simulation display that N, F-codoping promotes the electron transfer from Pt atoms to NFGC support, and leads to the d-band center shift upward, thus strengthening the oxidation degree of Pt active sites and increasing the composition of high-valent Ptx+. In-situ Raman analysis and density functional theory (DFT) results expound that F atoms embedding observably enhances the adsorption energy of Pt active centers to *OH intermediates, which not only significantly improves MOR catalytic activity, but also achieves efficient methanol dehydrogenation and alleviates CO poisoning. This customization of metal-support interface interaction by heteroatom doping strategy opens up opportunities for designing efficient supported catalysts.

The Effect of Thermal Action on the Change in the Chemical Composition of the Surface Layers of a Titanium Alloy, with a Sprayed Carbon Film, after Irradiation with N<sup>+</sup> Ions

The effect of thermal exposure under high vacuum conditions on the chemical composition of the surface layers of the VT6 alloy with mixed implantation of N+ ions by a carbon film is investigated. It is shown that under the conditions of thermal exposure, the change in the concentration profiles of the distribution of elements is determined by the processes of chemical interaction, in which the diffusion of carbon and nitrogen into deeper layers does not occur. On the contrary, their concentration decreases and this is due to the formation of volatile compounds CO, CO2 or (CH)2 under thermal exposure. Titanium in the surface analyzed layer is in an oxidized state with various degrees of oxidation. Up to a depth of about 10 nm, the oxidation state of titanium is Ti4+ and Ti3+, and in the transition region of the film/substrate is Ti2+.

Relationship between flavor characteristics and lipid oxidation in air-dried beef at different roasting stages

Lipid oxidation plays a key role in the formation of flavor during hot processing. The purpose of this study was to investigate the lipid oxidation, lipid molecular changes and their effects on flavor of air-dried beef at different roasting stages. The results revealed that the degree of lipid oxidation increased and the unsaturation of fatty acids decreased from 47.30% to 30.77%. A total of 48 volatile compounds were identified by headspace-solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). Notably, the types and contents of volatile compounds in S3 group exceeded those in S1 and S2, showing significant differences in the degree of separation among all groups. The aroma differences among the groups were associated with aromatic compounds formed by the oxidation of lipids. Moreover, a total of 59 lipids with significant differences were identified through liquid chromatography-tandem mass spectrometry (LC-MS/MS). These lipids may have major roles in the formation of aromatic compounds, particularly triglyceride, phosphatidylcholine, and lysophosphatidylcholine. This investigation elucidated the mechanisms for the flavor developments of air-dried beef during roasting stages.

New Derivatives of Modified Starch for Food Technology.

The food industry extensively uses chemically modified starches and their hydrolysates, which is mainly due to their emulsification ability. Therefore, it becomes inevitable to develop new starch derivatives, including modified starch hydrolysates, and effective preparation methods to meet the increasing demands of producers, consumers, and technology. This study comprehensively researches the physical, chemical, and functional properties (such as the water-binding capacity, swelling power, solubility, and fat absorption capacity) of chemically modified biopolymers and their enzymatic hydrolysis products. We utilized oxidized and acetylated potato and waxy-corn starches with varying degrees of substitution by carboxyl and acetyl groups in our research. The process of enzymatic hydrolysis was performed in a recirculated membrane reactor (CRMR). Our findings indicated that the physicochemical properties of starch derivatives and their hydrolysates depended on the biological origin of the biopolymer and the type and degree of modification. However, the presence of carboxyl groups in the modified starch molecules is critical and affects the rheological properties and water-binding capacity of the starch preparations. For example, in the case of waxy-corn starch preparations with a lower content of carboxyl groups (i.e., derivatives with a low degree of oxidation), the water-binding capacity (WBC) increases when compared to native starch. The highest WBC value of 206.3% was noted for the doubly modified waxy-corn starch with an oxidation degree of 0.2% and an acetylation degree of 2.5%, while native waxy-corn starch shows a WBC of 161.4%. In contrast, it was observed that preparations with a higher content of carboxyl groups, i.e., derivatives with an oxidation degree of 2.5%, show a lower swelling power compared to native waxy starch.

Reaction mechanism of catalytic gasification by calcium-based catalysts and oxidized coal residues in coalfield fire zones

Fires originating from coal spontaneous combustion within coalfields result not only in substantial coal resource depletion but also producing residual low-activity pyrolysis coal chars exhibiting varying degrees of oxidation. These chars develop progressively through successive heat penetration at the fire front and post-fire extinguishment phases. This paper focuses on the alkaline earth metal-activated catalytic gasification of residual oxidized coal in fire zones, constructs a carbon-based model of oxidized coal in fire zones. The results show that the reaction active sites of the oxidized coal carbon matrix model are mainly concentrated on the carbon atoms at the end of the aromatic ring. During catalytic gasification, the calcium-based catalyst engages with these active sites, forming a preliminary catalyst. The transformation of oxidized coal into CO primarily occurs through two distinct routes. Calcium attaches to the surface of the oxidized coal’s carbon-based structure, establishing active sites. Acting as a facilitator, it aids the movement of CO2 to the carbon-based surface, leading to its further breakdown into CO. The catalytic species containing calcium persistently amalgamates with active sites on coal coke surface, fostering the release of additional CO. Moreover, these catalytic species with calcium also bind CO2 and unite with active coal coke sites, generating carbon–oxygen complexes on the surface. These complexes are thermally unstable and decompose, yielding CO and initiating the formation of fresh active sites on the coal coke surface. Consequently, they interact further with calcium-based catalytic species, culminating in the creation of catalyst precursors, which drive a recurrent catalytic reaction process.

Graphene Oxide Nanosheets for Bone Tissue Regeneration.

Bone tissue engineering is a promising alternative to repair wounds caused by cellular or physical accidents that humans face daily. In this sense, the search for new graphene oxide (GO) nanofillers related to their degree of oxidation is born as an alternative bioactive component in forming new scaffolds. In the present study, three different GOs were synthesized with varying degrees of oxidation and studied chemically and tissue-wise. The oxidation degree was determined through infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron (XPS), and Raman spectroscopy (RS). The morphology of the samples was analyzed using scanning electron microscopy (SEM). The oxygen content was deeply described using the deconvolution of RS and XPS techniques. The latter represents the oxidation degree for each of the samples and the formation of new bonds promoted by the graphitization of the material. In the RS, two characteristic bands were observed according to the degree of oxidation and the degree of graphitization of the material represented in bands D and G with different relative intensities, suggesting that the samples have different crystallite sizes. This size was described using the Tuinstra-Koenig model, ranging between 18.7 and 25.1 nm. Finally, the bone neoformation observed in the cranial defects of critical size indicates that the F1 and F2 samples, besides being compatible and resorbable, acted as a bridge for bone healing through regeneration. This promoted healing by restoring bone and tissue structure without triggering a strong immune response.

Compositions and sources of fluorescent water-soluble and water-insoluble organic aerosols

Brown carbon (BrC), the light-absorbing component of organic aerosols, plays a significant role in climate change and atmospheric photochemistry. However, the water-insoluble fractions of BrC have not been extensively studied, limiting the assessment of the overall climate effects of BrC. In this study, water-soluble and -insoluble organic carbon (i.e., WSOC and WIOC) in wintertime aerosols in Hefei were subsequently fractionated, and their fluorescence properties were comparatively investigated with the excitation–emission matrix method. WIOC contributing 57.1 % was the major component of organic carbon. WSOC with the largest contribution from humic-like regions exhibited a redshift compared to WIOC. Three humic-like substances (HULIS) with different oxidation degrees and one protein-like substances (PRLIS) were identified as the major fluorescent components by the parallel factor analysis. WSOC had more highly oxygenated HULIS, whereas low-oxygenated HULIS dominated WIOC. Nighttime WIOC contained more less-oxygenated species. The positive matrix factorization analysis suggested that biomass burning (43 %) was the largest source of both fluorescent WSOC and WIOC. Coal combustion contributed much more to fluorescent WIOC (40 %), whereas secondary formation contributed more to fluorescent WSOC (12 %). During aerosol pollution episodes, the increase in fluorescence efficiency was much greater for WIOC (25 %) than for WSOC (12 %), and WSOC and WIOC experienced a redshift and blueshift in emission wavelength, respectively. WSOC had more highly oxygenated HULIS, while WIOC had more less-oxygenated HULIS in aerosol episodes than the non-episodic periods. In addition, aerosol pollution was accompanied by the increased contributions of biomass burning and coal combustion to both fluorescent WSOC and WIOC, while the decreased relative contribution of secondary formation to fluorescent WSOC. Our findings highlighted the different fluorescence properties, compositions and sources of fluorescent WSOC and WIOC, providing a comprehensive view of BrC aerosols.

Stabilizing Ti3C2Tx MXene flakes in air by removing confined water

MXenes have demonstrated potential for various applications owing to their tunable surface chemistry and metallic conductivity. However, high temperatures can accelerate MXene film oxidation in air. Understanding the mechanisms of MXene oxidation at elevated temperatures, which is still limited, is critical in improving their thermal stability for high-temperature applications. Here, we demonstrate that Ti[Formula: see text]C[Formula: see text]T[Formula: see text] MXene monoflakes have exceptional thermal stability at temperatures up to 600[Formula: see text]C in air, while multiflakes readily oxidize in air at 300[Formula: see text]C. Density functional theory calculations indicate that confined water between Ti[Formula: see text]C[Formula: see text]T[Formula: see text] flakes has higher removal energy than surface water and can thus persist to higher temperatures, leading to oxidation. We demonstrate that the amount of confined water correlates with the degree of oxidation in stacked flakes. Confined water can be fully removed by vacuum annealing Ti[Formula: see text]C[Formula: see text]T[Formula: see text] films at 600[Formula: see text]C, resulting in substantial stability improvement in multiflake films (can withstand 600[Formula: see text]C in air). These findings provide fundamental insights into the kinetics of confined water and its role in Ti[Formula: see text]C[Formula: see text]T[Formula: see text] oxidation. This work enables the use of stable monoflake MXenes in high-temperature applications and provides guidelines for proper vacuum annealing of multiflake films to enhance their stability.