Atomic Force Research Articles

Utilization of a Solid Waste Inhibitor for the Clean Flotation Enrichment of Phosphate Ores.

The accumulation of phosphogypsum (PG) in the phosphorus chemical industry poses significant environmental challenges. Therefore, developing a harmless utilization method is crucial for alleviating these burdens and promoting sustainable industry practices. In this study, PG was used as a flotation inhibitor, enabling the flotation separation of apatite and dolomite based on the main components and dissolution behavior of PG. A microflotation study revealed that 0.875 g/L PG selectively inhibited dolomite when the sodium oleate (NaOL) concentration was 1.5 × 10-4 mol/L, reducing dolomite recovery 76% to 10% at pH in the range of 7-11. Conversely, apatite recovery remained above 90% at pH 7-9 and was only slightly inhibited at pH in the range of pH 9-11. When CaSO4·2H2O and CaHPO4·2H2O were added as flotation inhibitors, they also inhibited dolomite, though their effects were weaker than PG. Measurements of contact angles, zeta potentials, and adsorption capacities indicated that PG enhanced the hydrophilicity of dolomite, hindering NaOL adsorption thereon, while it had little effect on the floatability of apatite. Atomic force and scanning electron microscopy revealed selective PG was adsorbed on the dolomite surface, altering its properties, while PG was weakly adsorbed on the apatite surface and had minimal impact on its properties. The solution chemical composition and microthermal results showed that CaSO4 and CaHPO4 are the effective components of PG inhibition. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry confirmed that CaSO4 and CaHPO4 in PG were selectively adsorbed at Ca and Mg ion sites on the dolomite surface. Molecular dynamics simulations showed that CaSO4 interacts with the surface of dolomite, and CaHPO4 can promote the adsorption of CaSO4 on the surface of dolomite. Utilizing PG as a flotation inhibitor provides a novel approach for the environmentally safe use of PG resources.

Machine learning potential model for accelerating quantum chemistry‐driven property prediction and molecular design

AbstractQuantum chemistry (QC) calculations have significantly advanced the development of materials, drugs, and other molecular products. Molecular geometry optimization is an indispensable step for QC calculations. However, its computational cost increases dramatically with increasing molecular system complexity, hindering the large‐scale molecule screening. This work proposes a deep learning‐based molecular potential energy surface prediction tool (DeePEST) to significantly accelerate geometry optimizations. The key of DeePEST involves the development of a novel machine learning potential model for accurate and fast predictions of molecular energy and atomic forces. These predictions enable efficient molecular geometry optimizations for subsequent predictions of QC properties (single‐point energy, dipole moment, HOMO/LUMO, and 13C chemical shifts) and COSMO‐SAC‐based thermodynamic properties (activity coefficient). Moreover, DeePEST facilitates efficient computer‐aided molecular designs that involve QC‐based geometry optimizations. The utilization of DeePEST in geometry optimizations achieves high prediction accuracy approaching to rigorous QC methods while maintaining the computational efficiency of molecular mechanics methods.

Microbe-mediated synthesis of defect-rich CeO2 nanoparticles with oxidase-like activity for colorimetric detection of L-penicillamine and glutathione.

To enhance production efficiency, curtail costs, and minimize environmental impact, developing simple and sustainable nanozyme synthesis methods has been the focus of relevant research. In this report, graphite-coated CeO2 nanoparticles (CeO2 NPs) with multiple defects (Ce3+ defects, oxygen vacancies and carbon defects) were synthesized via the culture filtrate of the extremely radioresistant bacterium Deinococcus wulumuqiensis R12 (D. wulumuqiensis R12). The as-prepared CeO2 NPs exhibit remarkable oxidase (OXD)-like activity, efficiently catalyzing the oxidation of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) to form oxTMB, even in the absence of H2O2. The electron-rich bioactive substances in the supernatant were demonstrated to modulate the electronic state of the Ce atom and played a key role in the formation of multiple defects, thereby enhancing the OXD-like activity of CeO2 NPs. Based on the inhibitory effect of sulphydryl groups (-SH) on the TMB-CeO2 system, a colorimetric strategy for the detection of both L-penicillamine (L-PA) and glutathione (GSH) was devised and successfully applied in real sample analysis. The linear ranges of L-PA and GSH detection were found to be 10-500 μM and 9-200 μM with the limits of detection (LODs) at 8.53 and 5.19 μM, respectively. This work provides a straightforward, eco-friendly and nontoxic method for the synthesis and defect construction of CeO2 NPs with OXD-like activity.

The charge transfer of Au adsorption on CeO<sub>2</sub>(111) surface

Au/CeO<sub>2</sub>(111), as an important catalyst system, has demonstrated excellent catalytic performance in a variety of fields such as the catalytic oxidation and the water-gas shift reactions. In order to deeply reVeal Au/CeO<sub>2</sub>(111) catalytic mechanism, especially to understand the interaction of the active components on the atomic scale. In this paper, the adsorption properties on the Au/CeO<sub>2</sub>(111) surface are investigated by calculating the adsorption energy, differential charge density, Bader charge, and the density of states using density functional theory (DFT+U). First, five adsorption sites of Au/CeO<sub>2</sub>(111) were identified in the planar region of CeO<sub>2</sub>(111), and the most stable adsorption configuration was found to be located at the bridging position between surface oxygen atoms (the oxygen-oxygen bridging site). It suggests that Au interacts more closely with the oxygen-oxygen bridging sites. Further, the differential charge density and Bader charge reVeal the charge transfer mechanism during the adsorption process: the Au atoms are oxidized to Au<sup>+</sup>, while the Ce<sup>4+</sup> ions in the second nearest neighbor of Au are reduced to Ce<sup>3+</sup>, and the adsorption process is accompanied by a charge transfer phenomenon. Au also exhibits a unique adsorption behavior in the CeO<sub>2</sub>(111) step-edge region, where a highly under-allocated environment is formed due to the decrease in the coordination number of atoms in the step edge, which enhances the adsorption of Au in a highly under-allocated environment. The adsorption of Au at the step edge is enhanced by the lower coordinated environment due to the reduced coordination number of the atoms at the step edge. By comparing four different types of step structures (Type I, Type II, Type II*, and Type III), we find that the higher adsorption energies of Au at the Type II* and Type III sites are mainly attributed to the lower coordinated state of Ce atoms at these sites. Charge transfer is also particularly pronounced at the Type III sites. It is also accompanied by electron transfer from Au to Ce<sup>4+</sup> ions, making Type III the preferred adsorption site for Au atoms. By constructing a more comprehensive Au/CeO₂ model, this study breaks through the preVious limitation of focusing only on planar adsorption and reVeals the adsorption mechanism of Au/CeO₂ at the edge of the step, which provides a new perspective for us to deeply understand the catalytic mechanism of Au/CeO₂(111).

A study of rare earth intermetallide La<sub>0.73</sub>Dy<sub>0.27</sub>Mn<sub>2</sub>Si<sub>2</sub> by Raman spectroscopy, magnetic force microscopy and resonance photoemission spectroscopy

The features of the magnetic microstructure of La0.73Dy0.27Mn2Si2 at 293 K have been visualized by atomic force and magnetic force microscopy. Magnetic force images reveal the presence of low-contrast magnetic domains. The change of Raman spectral characteristics of light scattering in the process of cooling La0.73Dy0.27Mn2Si2 to a temperature of 263 K is experimentally detected. The electronic structure of La0.73Dy0.27Mn2Si2 is investigated by resonance photoemission spectroscopy with the use of the synchrotron radiation. Resonances at 3d and 4d levels of electronic structure show different properties of valence electrons. Using the 3d–4f (M4.5 absorption edge) resonance, the distribution of 4f states of dysprosium in the valence band is determined. Photoemission upon the giant Dy 4d–4f (N4.5 absorption edge) resonance is determined by the contribution of all states in the valence band due to the sudden involvement of the Coulomb interaction. The energies of La and 4f levels of La, the 4f level of Dy, and the 3d level of Mn in the valence band have been determined.

Surface Hydroxyl Groups Functionalized Porous CeO2 for Enhanced Selective Adsorption of As(III).

The adsorption technique has been considered as one of the promising methods to remove arsenic ions in aqueous systems. However, the adsorbents are usually poorly selective and have low capacity. Herein, a kind of porous CeO2 containing surface hydroxyl group which synthesized facilely possesses the great performance of selective adsorption of As(III) with 98.57% removal against 14 other coexisting metal ions. The results showed that the processes of As(III) and As(V) uptake were heterogeneous monolayer adsorptions and included external and intraparticle diffusions. The adsorption capacities at pH 2.5 reached 111.24 and 56.89 mg/g for As(III) and As(V), respectively. In addition, it also showed that As(III) could be oxidized to As(V) in the adsorption process. Density functional theory calculations revealed that the OH group in H3AsO30 and the As atom in H3AsO40 have affinity with lattice oxygen (O2-) in CeO2, while the O atom in H2AsO4- preferred the Ce atom in CeO2. This study provides a novel porous CeO2 containing hydroxyl groups for selective and efficient removal of arsenic and elucidates the mechanism of As(III) and As(V) adsorptions.

Structural and Physical Properties of the Heavy Fermion Metal Ce2NiAl6Si5

Abstract Strongly correlated electrons at the verge of quantum criticality give rise to unconventional phases of matter and behaviors, with the discovery of new quantum critical materials driving synergistic advances in both experiments and theory. In this work, we report the structural and physical properties of a new quaternary Ce-based heavy fermion compound, Ce$_2$NiAl$_6$Si$_5$, synthesized using the self-flux method. This compound forms a layered tetragonal structure (space group $P4/nmm$), with square nets of Ce atoms separated by Si-Al or Ni-Si-Ge layers. Specific heat measurements show a low-temperature Sommerfeld coefficient of 1.4 J/mol-Ce K$^2$, with a reduced entropy indicative of significant Kondo interactions. Below 0.6 K, an upturn in resistivity and a deviation in magnetic susceptibility suggest the appearance of magnetic ordering or the development of dynamic magnetic correlations, which is further supported by a bulge in specific heat around 0.4 K. These results suggest that Ce$_2$NiAl$_6$Si$_5$ is a layered heavy fermion metal, naturally located in proximity to a spin-density-wave quantum critical point.

Tuning the morphology and energy levels in organic solar cells with metal–organic framework nanosheets

Metal–organic framework nanosheets (MONs) have proved themselves to be useful additives for enhancing the performance of a variety of thin film solar cell devices. However, to date only isolated examples have been reported. In this work we take advantage of the modular structure of MONs in order to resolve the effect of their different structural and optoelectronic features on the performance of organic photovoltaic (OPV) devices. Three different MONs were synthesized using different combinations of two porphyrin-based ligands meso-tetracarboxyphenyl porphyrin (TCPP) or tetrapyridyl-porphyrin (TPyP) with either zinc and/or copper ions and the effect of their addition to polythiophene-fullerene (P3HT-PC71BM) OPV devices was investigated. The power conversion efficiency (PCE) of devices was found to approximately double with the addition of MONs of Zn2(ZnTCPP) -4.7% PCE, 10.45 mA/cm2 short-circuit current density (JSC), 0.69 open-circuit voltage (VOC), 64.20% fill-factor (FF), but was unchanged with the addition of Cu2(ZnTPyP) (2.6% PCE, 3.68 mA/cm2JSC, 0.59 VOC, 46.27% FF) and halved upon the addition of Cu2(CuTCPP) (1.24% PCE, 6.72 mA/cm2JSC, 0.59 VOC, 56.24% FF) compared to devices without nanosheets (2.6% PCE, 6.61 mA/cm2JSC, 0.58 VOC, 56.64% FF). Our analysis indicates that there are three different mechanisms by which MONs can influence the photoactive layer – light absorption, energy level alignment, and morphological changes. Analysis of external quantum efficiency, UV–vis and photoelectron spectroscopy data found that MONs have similar effects on light absorption and energy level alignment. However, atomic force and Raman microscopy studies revealed that the nanosheet thickness and lateral size are crucial parameters in enabling the MONs to act as beneficial additives resulting in an improvement of the OPV device performance. We anticipate this study will aid in the design of MONs and other 2D materials for future use in other light harvesting and emitting devices.

PLLA honeycombs activated by plasma and high-energy excimer laser for stem cell support

In this study, we constructed and activated honeycomb structures on perfluorinated substrates subjected to KrF laser treatment (wavelength 248 nm). We selected the biopolymer poly L-lactic acid (PLLA) as the honeycomb material, which was dissolved in a mixture of chloroform/methanol. A micropattern of a plasma-treated perfluorethyleneperopylene (FEP) substrate was prepared by improved phase separation during dip-coating. The PLLA micropattern was subsequently treated with an excimer laser with a laser fluence of 10 mJ.cm-2 and with a different number of laser pulses. Alternatively, plasma exposure can be used as a secondary treatment. The surface morphologies of the pristine and laser-treated PLLA patterns were studied using atomic force and scanning electron microscopy. The surface chemistry was analyzed using energy-dispersive spectroscopy and X-ray photoelectron spectroscopy. In addition, the metabolic activity of adipose stem cells was evaluated using the MTS test, and cell numbers in selected samples were determined. The morphology of cells growing in the honeycomb-like pattern was studied in detail using fluorescence microscopy. In all, we used a combination of honeycomb pattern (HCP) laser treatment and plasma treatment to construct an optimal scaffold for adipose stem cell culture.

Regulation of electron density in Pt nanoparticles via bimetallic metal-organic frameworks for enhancing photothermal catalysis of toluene decomposition

Volatile Organic Compounds (VOCs) are omnipresent in the sphere of human industrial, harboring latent adverse consequences for health and the ecological system. The photothermal catalytic oxidation of VOCs is an advanced integrated technology that harnesses the combined effects of light and heat energy to enhance the efficiency of VOCs degradation. Herein, a bimetallic Metal-Organic Framework (MOF) was synthesized with the incorporation of Ce into the UiO-66-NH2(Zr) (i.e., UNH(Zr)), UiO-66-NH2(Zr2Ce) (i.e., UNH(Z2C)), which was achieved with Ce atom substituting for a portion of Zr atom within the Zr-oxo clusters. Pt nanoparticles (NPs) are integrated with MOFs to form composites using the dual-solvent method. Ce-oxo fulfills a bifunctional role: it not only facilitates the enhancement of the ligand-to-metal charge transfer (LMCT), but also establishes interaction with Pt NPs. Ce-oxo mediates an enhancement of electron density on Pt NPs. This phenomenon enhances the adsorption and activation of oxygen, significantly boosting the photocatalytic performance for toluene degradation, as demonstrated by a reduction of 30 ℃ for complete mineralization of toluene as compared to that of Pt@UiO-66-NH2(Zr) (i.e., PUNH(Zr)). This study potentially offers new insights into the relationship between electron transfer effects in bimetallic MOF-based catalysts and their efficient catalytic performance for VOCs degradation.

Isomorphously substituted cerium induced oxygen vacancy and medium basicity in Ni/fibrous silica catalyst for superior low-temperature CO2 methanation

A series of promoters (Ce, La, Mo, and Zr) was introduced into the Ni/CHE-SM catalyst by using the impregnation method and tested for CO2 methanation. Among these, Ni-Ce/CHE-SM possessed a high CO2 conversion of 80 % at 250 °C, signifying its potential at low temperature. The superior performance of Ni-Ce/CHE-SM was attributed to the formation of Si-O-Ni and Si-O-Ce species, as confirmed by FTIR-KBr analysis. XPS and CO2-TPD analyses revealed an abundance of oxygen vacancies existed within Ni-Ce/CHE-SM, resulting in enhancement of basicity amount and strength. In addition, Raman analysis showed the existence of three and four silica member rings which was believed that the Si atom be substituted with the Ce atom, thus contributing to create more oxygen vacancies. Hence, additional active sites were provided which enhance the adsorption of reactant molecules and improve the production of CH4, thus emphasizing the greater potential of Ni-Ce/CHE-SM in CO2 methanation application.

Antimicrobial and antibiofilm potential of α-MSH derived cationic and hydrophobic peptides against Escherichia coli: Mechanistic insight through peptide-lipopolysaccharide interactions

The prevalence of infections caused by various Gram-negative pathogens specifically Escherichia coli continuously poses a significant challenge in health care as well as community settings owing to their ability to form biofilm and escalating tolerance towards available antibiotics. While most treatment regimes are targeted at eliminating the E. coli cells, the pathogenicity factors called endotoxin (lipopolysaccharides), associated with the sepsis initiation and the leading cause of death in intensive care units globally, are often ignored. In this study, the potency of alpha-melanocyte stimulating hormone based-peptides, particularly Ana-9 and Ana-10 against E. coli was investigated through microbiological, biophysical, and microscopic assays. Both Ana-9 and Ana-10 demonstrated enhanced activity against planktonic E. coli cells, and retained their activity against biofilm, which was supported by confocal microscopy. From the mechanistic perspective, spectroscopic studies indicated that the binding of peptides with LPS led to structural alteration of peptides due to their insertion into the hydrophobic environment of LPS. The electrostatic interaction of the peptide with LPS leads to outer membrane disorganization, allowing the peptide to access the inner membrane, depolarize it and ultimately inhibit the bacterial cells within the biofilm. These observations were further confirmed by atomic force and scanning electron microscopy. Thus, this study deepens our understanding of the structural characteristics of peptides attached to LPS, which could lead to the gradual improvement in developing more potent, broad-spectrum endotoxin neutralizers.

Mn−Ce Symbiosis: Nanozymes with Multiple Active Sites Facilitate Scavenging of Reactive Oxygen Species (ROS) Based on Electron Transfer and Confinement Anchoring

AbstractRegulating appropriate valence states of metal active centers, such as Ce3+/Ce4+ and Mn3+/Mn2+, as well as surface vacancy defects, is crucial for enhancing the catalytic activity of cerium‐based and manganese‐based nanozymes. Drawing inspiration from the efficient substance exchange in rhizobia‐colonized root cells of legumes, we developed a symbiosis nanozyme system with rhizobia‐like CeOx nanoclusters robustly anchored onto root‐like Mn3O4 nanosupports (CeOx/Mn3O4). The process of “substance exchange” between Ce and Mn atoms—reminiscent of electron transfer—not only fine‐tunes the metal active sites to achieve optimal Ce3+/Ce4+ and Mn3+/Mn2+ ratios but also enhances the vacancy ratio through interface defect engineering. Additionally, the confinement anchoring of CeOx on Mn3O4 ensures efficient electron transfer in catalytic reactions. The final CeOx/Mn3O4 nanozyme demonstrates potent catalase‐like (CAT‐like) and superoxide dismutase‐like (SOD‐like) activities, excelling in both chemical settings and cellular environments with high reactive oxygen species (ROS) levels. This research not only unveils a novel material adept at effectively eliminating ROS but also presents an innovative approach for amplifying the efficacy of nanozymes.

Harnessing 4f Electron Itinerancy for Integrated Dual-Band Redox Systems Boosts Lithium-Oxygen Batteries Electrocatalysis.

In-depth comprehension and manipulation of band occupation at metal centers are crucial for facilitating effective adsorption and electron transfer in lithium-oxygen battery (LOB) reactions. Rare earth elements play a unique role in band hybridization due to their deep orbitals and strong localization of 4 f electrons. Herein, we anchor single Ce atoms onto CoO, constructing a highly active and stable catalyst with d-f a dual-band redox center. It is discovered that the itinerant behavior of 4 f electrons introduces an enhanced spin-orbit coupling effect, which facilitates ideal σ/π bonding and flexible adsorption between the Ce/Co active sites and *O. Simultaneously, the injection of localized Ce 4 f electrons strengthens the orbital bonding capacity of Co-O, effectively inhibits the dissolution of Co sites and improves the structural stability of the cathode material. Bracingly, the Ce1/CoO-based LOB exhibits an ultra-low charge-discharge polarization (0.46 V) and stable cyclic performance (1088 hours). This work breaks through the traditional limitations in catalyst activity and stability, providing new strategies and theoretical insights for developing high-performance LOBs powered by rare-earth elements.

Antimicrobial activity of CuFe2O4 and CuFe2O4/ZnO: Squaring colorimetric and traditional microbiology assays with atomic force- and holotomography-microscopies

Intensive research efforts seek the discovery of efficient antimicrobial compounds to fight microbial resistance. Magnetic nanoparticles represent a promising option due to their multifunctional antimicrobial properties, as well as their versatility, stability, and the limited microbial resistance they generate. In this study, magnetic nanomaterials (MNMs) are synthesized using a microwave-activated solvothermal method. Characterization data indicate the crystalline nature (cubic spinel CuFe2O4 NMs), superparamagnetic behavior (MCF = 52 emu/g and MCF-ZnO = 29 emu/g) nanometric and regular size (spherical particles with a mean size of 7.4 ± 1.3 nm) of the MNMs. The antimicrobial activity of the as-prepared (naked) MNMs is moderate against bacteria, yeast, and fungal strains due to the aggregation of the MNMs in the exposure media. However, citrate-functionalized MNMs (CuFe2O4-Cit, CF-Cit) show enhanced antimicrobial activity, further increasing upon activation under a high-frequency magnetic field (magnetic hyperthermia). CF-Cit exerts stronger antibacterial activity towards S. aureus (MIC <25 μg/mL) than E. coli (MIC <50 μg/mL In addition, CuFe2O4-ZnO composites were synthesized and fully characterized. The MNMs under study exhibit efficient antifungal and anti-biofilm activity. Working towards the sustainable development of multifunctional (CuFe2O4 and CuFe2O4-ZnO) MNMs, their compatibility and bioactivity was evaluated using traditional assays and advanced microscopy techniques (Atomic Force Microscopy-AFM and Holotomographic Microscopy -HTM). Because of their chemical composition, the MNMs under study lixiviate transition metal ions to the exposure media, interfering with traditional colorimetric assays used to evaluate the bioactivity of the MNMs (antimicrobial, biocompatibility). Thus, AFM and HTM studies render complementary information during the interpretation of the bioactivity mechanisms exhibited by the MNMs.

Cyclic and helical symmetry-informed machine learned force fields: Application to lattice vibrations in carbon nanotubes

We present a formalism for developing cyclic and helical symmetry-informed machine learned force fields (MLFFs). In particular, employing the smooth overlap of atomic positions descriptors with the polynomial kernel method, we derive cyclic and helical symmetry-adapted expressions for the energy, atomic forces, and phonons, i.e., lattice vibration frequencies and modes. We use this formulation to construct a symmetry-informed MLFF for carbon nanotubes (CNTs), where the model is trained through Bayesian linear regression, with the data generated from ab initio density functional theory (DFT) calculations performed during on-the-fly symmetry-informed MLFF molecular dynamics simulations of representative CNTs. We demonstrate the accuracy of the MLFF model by comparisons with DFT calculations for the energies and forces, and density functional perturbation theory calculations for the phonons, while considering CNTs not used in the training. In particular, we obtain a root mean square error of 1.4×10−4 Ha/atom, 4.7×10−4 Ha/Bohr, and 4.8 cm−1 in the energy, forces, and phonon frequencies, respectively, which are well within the accuracy targeted in ab initio calculations. We apply this framework to study phonons in CNTs of various diameters and chiralities, where we identify the torsional rigid body mode that is unique to cylindrical structures and establish laws for variation of the phonon frequencies associated with the ring modes and radial breathing modes. Overall, the proposed formalism provides an avenue for studying nanostructures with cyclic and helical symmetry at ab initio accuracy, while providing orders-of-magnitude speedup relative to such methods.

Insight into formaldehyde decomposition over MOFs-derived CeO2-MnOx bimetallic oxides

The ubiquitous presence of formaldehyde as a pollutant has aroused significant environmental and health concerns. The design and performance of (OR: transition metal oxide) catalysts in the catalytic oxidation method continue to face a myriad of challenges. Herein, a series of CeO2-x-MnOx catalysts are synthesized using manganous nitrate impregnated Ce-metal–organic-frameworks as the precursor, followed by a traditional calcination step. Interestingly, we found that the gases released during the pyrolysis of metal–organic-frameworks significantly affect the valence states of Ce and Mn, which are key factors responsible for catalytic activity. Characterizations results show that the CeO2-x-MnOx-2.5 sample contains a large amount of Ce3+, a high Mn3+/Mn4+ ratio, and an abundance of reactive oxygen species on its surface. Density functional theory results demonstrate that oxygen vacancies not only effectively suppress charge loss of Mn and Ce atoms but also significantly enhance the adsorption strength of CeO2-x-MnOx-2.5 for both formaldehyde and O2. These structural features jointly influence the adsorption as well as the rapid oxidation of formaldehyde molecules, leading to the excellent catalytic performance towards formaldehyde oxidation. This study provides a promising platform for designing straightforward, cost-effective, and highly efficient bimetallic catalysts suitable for low-temperature formaldehyde oxidation.

Mechanism and kinetic study of n-undecane degradation on Co-CeO2: A dual approach combining thermal and plasma catalysis

The catalytic degradation of long-chain alkanes presents a formidable challenge in environmental chemistry. n-Undecane (C11), a quintessential long-chain alkane, predominates as a component of volatile organic compounds (VOCs) emitted from the printing industry and diesel-powered vehicles. The uncontrolled release of these compounds into the atmosphere necessitates stringent measures. This study reports on the plasma-catalytic degradation of n-undecane over the CeO2 based catalysts cooperated with cobalt (Co), manganese (Mn), aluminum (Al), nickel (Ni), iron (Fe), or magnesium (Mg) via aerosol pyrolysis method. Notably, the Co-doped CeO2 catalyst with a Co:Ce atom ratio of 4:1, in conjunction with plasma, achieves an optimal degradation performance. Under the reaction conditions of 90 °C and an energy density of 40 J/L, C11 conversion and COx selectivity reached impressive levels of 100 % and 97 %, respectively. Characterization findings indicate that elevated ratios of Ce3+/(Ce3++Ce4+) and Co3+/(Co2++Co3+) are conducive to the catalytic degradation of C11. A kinetic model has been developed to elucidate the thermal and plasma catalytic degradation mechanisms.

Atomically dispersed Ir Lewis acid sites on (111)-oriented CeO2 enable enhanced reaction kinetics for Li-O2 batteries

Non-aqueous lithium-oxygen batteries are widely regarded as one of the most promising electrochemical energy storage systems, with their ultra-high theoretical energy density and environmental friendliness. However, the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics hinder their practical application. In this study, we tailored an atomically dispersed Ir site on a CeO2 support (Ir@CeO2) with {111} facet-dependent activity to enhance cathode reaction kinetics. The charge interaction between Ir and Ce atoms results in the appropriate regulation of the d-band center of Ir sites leaping into the Fermi energy level, demonstrating a stronger Lewis acidity, which enables easier electron injection from the Ir d-orbitals into O 2p-orbitals of LiO2. This facilitates the conversion kinetics, and as a result, the lithium-oxygen battery with Ir@CeO2 catalyst delivers a minimal discharge/charge polarization and long-term cycle stability, outperforming most traditional catalysts reported. Our promising findings offer compelling insights into the precise manipulation of d orbital structures and the optimization of Lewis acidity, paving the way for advanced electrocatalyst design.

Predictions of spin-valley properties in ferromagnetic Janus 2H-CeXY (X, Y = Cl, Br, I, X ≠ Y) monolayers: Merger of valleytronics with spintronics

In this work, the Janus 2H-CeXY monolayers are predicted as 2D intrinsic ferrovalley materials with bipolar ferromagnetic (FM) semiconductor characters, high Tc of 511–540 K, robust in-plane/perpendicular magnetic anisotropy (IMA/PMA) and spontaneous valley polarization through first-principles calculations. The d-p-d indirect exchange interaction between the Ce atom and X(Y) atoms is responsible for the observed FM ordering. Applying the biaxial strain ε from −6 % to 6 %, the Janus 2H-CeXY monolayers keep energy bandgap and large magnetic anisotropy. While a transition from PMA to IMA character is observed for the 2H-CeBrCl monolayer, which is due to the competition between Ce-p/d and Br/Cl-p orbitals. The intrinsic magnetic interaction and strong SOC effect induce a large spontaneous valley polarization of 29.1–78.7 meV for the Janus 2H-CeXY monolayers, which is also robust under various ε. Besides, the anomalous valley Hall effect (AVHE) can be observed due to the nonzero Ωz(k) induced by the broken space/time-reversal symmetry. Overall, the Janus 2H-CeXY monolayers provides a new candidate for the spintronic and valleytronic devices.