Adsorption Activity Research Articles

Fe reaction sites enhance the removal of tetracycline over Fe-Bi3O4Br with intensified adsorption and photocatalysis

An adsorption-coupling photocatalytic degradation system is a promising strategy for removing emerging pollutants with coexisting substances. Here, Fe-Bi3O4Br was designed and prepared via a hydrothermal method, which intensified tetracycline adsorption and reactive oxygen species formation originated from molecular oxygen. The improvements in adsorption and photocatalytic activity enhanced the generation and utilization of active species, leading to an increase of over 30 % in removal efficiency of tetracycline. Adsorption experiments proved that Fe doping optimized the specific surface area and the dominant crystal plane (020), which was beneficial for ion exchange adsorption of tetracycline. For photocatalytic degradation, the introduced Fe (Fe3+/Fe2+ redox pathway) acted as the reaction sites for molecular oxygen activation and as the enrichment sites for photogenerated electrons, leading to a lower recombination rate of photogenerated electrons and holes. With the influence of Fe doping, more ∙O2- (approximately 1.8 times) were produced for degradation. This study clarified the mechanism of Fe doping on pollutant adsorption and molecular oxygen activation for bismuth-rich materials, as well as a reference for antibiotic removal via adsorption coupling degradation.

Comparing low-temperature NH3-SCR activity, operating temperature window and kinetic properties of the Mn-Fe-Nb/TiO2 catalysts prepared by different methods

In order to overcome the shortcomings of traditional V-based catalysts, such as poor low-temperature activity, narrow temperature window, and toxicity. Therefore, the Mn-Fe-Nb/TiO2 catalysts were prepared using impregnation (IM), citric acid complexation (CA), co-precipitation (CP), hydrothermal synthesis (HY), and sol–gel (SG) methods to develop novel NH3 selective catalytic reduction (NH3-SCR) catalysts with excellent low-temperature activity, a wide temperature window, and environmental friendliness. Their NH3-SCR catalytic activity was evaluated, followed by a detailed analysis of their morphology, structure, specific surface area, chemical state, redox properties, acidity, and interactions using X-ray diffraction (XRD), Bruaner-Emmet-Teller (BET), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), NH3 temperature-programmed desorption (NH3-TPD), and Fourier transform infrared spectroscopy (FTIR) techniques. The 5Mn-7Fe-4Nb/TiO2-SG catalyst, prepared via sol–gel, exhibited the highest denitrification (de-NOx) activity and the widest operating temperature window, achieving over 80% Nitric oxide (NO) conversion at 180–350 °C and a peak conversion of 97% at 250 °C. The XRD, BET, SEM, and HR-TEM characterization results showed that the catalyst prepared using the sol–gel method had the smallest particles, the highest specific surface area, and the greatest dispersion. XPS and NH3-TPD results revealed that the catalyst prepared using the sol–gel method possessed the highest surface adsorbed oxygen (Oα) content and the largest number of acidic sites. H2-TPR and FTIR analyses indicated that the catalyst prepared using the sol–gel method enhanced the reduction capacity and possessed the strongest interaction forces among support-active-promoter components. Steady-state kinetic tests confirmed that in the NH3-SCR reaction, the rate-determining step was the adsorption activation of NO on the catalyst surface. The sol–gel method reduced the activation energy for de-NOx reactions, enhancing the low-temperature activity of the catalyst.

Restructuring surface frustrated Lewis pairs of MgAl-LDH through isomorphous Co doping for accelerating photocatalytic CO2 reduction

The adsorption of carbon dioxide on the catalyst surface is often neglected, and the improvement of adsorption activation capacity is important to realize the efficient conversion of carbon dioxide. In this paper, a novel layered double hydroxide Co-MgAl-LDH (CML) with frustrated Lewis pairs (FLPs) was successfully prepared by one-step hydrothermal doping of transition metal Co, which Co2+ and the oxygen vacancies brought about by the doping (Co2+-Vo) are the Lewis acid site, and adjacent hydroxyls are the Lewis base site, and In-situ experiments and Density Functional Theory (DFT) demonstrated that the FLPs effectively enhanced the CO2 adsorption activation capacity of CML. The present work provides a new idea for modifying Layered double hydroxides (LDH) to construct FLPs, and also offers new hope for constructing high-performance LDH-based CO2 reduction photocatalysts.

Dissociative Oxygen Adsorption and Incorporation in Co3O4-Dispersed BaZr0.9Sc0.1O2.95 for PCFC Cathode.

The development of air electrodes with superior surface oxygen exchange properties at intermediate temperatures is crucial for improving the efficiency of protonic ceramic fuel cells. This study evaluated the surface exchange properties of Co3O4 dispersed protonic conductors, BaZr0.9Sc0.1O2.95. Although Co3O4 is widely acknowledged as superior dissociative adsorption catalysts, there is still ambiguity regarding the enhancement mechanisms of their surface exchange properties by Co3O4, as well as their optimal composition to achieve high catalytic activity. To overcome these difficulties, this study elucidated the effect of the chemical states and composition of composites on their surface exchange properties by evaluating their chemical states and surface exchange reaction rates with several compositions prepared at different temperature conditions using a vibrating-sample magnetometer and the pulse isotope exchange technique. For samples annealed at a high temperature, it became evident that the surface exchange activity became the most active by adding only 1 vol % Co3O4 and indicated an abrupt decline above this composition despite an increase in the volume of the catalysts. This was attributed to the combined effect of the high dissociative adsorption activity of the Co-containing solid solutions formed at a high temperature and a decrease in oxygen vacancies due to hole compensation. For samples annealed at intermediate temperature, their chemical states remained unchanged from those of the original milled powders, and their surface exchange properties monotonically improved with an increase in the volume of Co3O4. Based on the results, different chemical states of composites derived from different preparation conditions lead to completely different activation behavior of the surface exchange reaction.

Elevated efficiency in tartrazine removal from wastewater through boron-doped biochar: enhanced adsorption and persulfate activation

Boron-doped biochar (B-BC) was synthesized by pyrolysis using solid waste of sorghum straw as raw material. The specific surface area of B-BC increased significantly by 2.38 times compared to that of pure BC. This enhancement allowed B-BC (0.3 g L−1) to achieve complete adsorption of 10 mg L−1 tartrazine (TTZ) within 40 min. Moreover, acidic conditions were more favorable for TTZ adsorption, achieving complete removal of TTZ in only 15 min at a pH of 3.0. Interestingly, the adsorption rate of TTZ by B-BC in the presence of 0.05 M Cl− was approximately 2.12 times higher than that in the absence of Cl−. When other background electrolytes were present, excluding PO43−, complete adsorption of TTZ could also be achieved within 60 min. Thermodynamic analysis and DFT calculations described the parameters of B-BC for TTZ adsorption, including ΔGΘ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta {\ ext{G}}^{\\Theta }$$\\end{document} (< 0 kJ mol−1), ΔHΘ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta {\ ext{H}}^{\\Theta }$$\\end{document} (− 2.199 kJ mol−1), ΔSΘ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta {\ ext{S}}^{\\Theta }$$\\end{document} (− 6.068 J mol−1 K−1), and the adsorption energy (Eads = − 0.6919 eV), indicating a tendency towards a spontaneous adsorption process. Moreover, the strong electron transfer ability of B-BC and the oxygen-containing groups promoted the activation of PDS and generation of active substances such as 1O2, O2•−, and SO4•−, thereby degrading TTZ into products with lower biological toxicity. When the added PDS was only 0.1 mM, the degradation rate constant of TTZ could reach 0.1481 min−1. Furthermore, boron doping enhanced the stability of biochar, enabling the complete removal of 10 mg L−1 TTZ even after recycling and regeneration. In summary, this study offers a practical solution for the resource utilization of solid waste sorghum straw and the treatment of TTZ-polluted wastewater.Graphical

Synergistic improvement of the sulfur redox reaction by MOF-driven dual-defect polyhedral Mn-doped Co1-xS embedded in an N-doped carbon composite host for practical lithium-sulfur batteries

In the quest for practical sulfur hosts for lithium-sulfur batteries, a novel approach has been delineated. By meticulously adjusting the Mn:Co (1:5/1:9/1:1) ratio and the sulfidation temperature, a series of nitrogen-doped carbon nanopolyhedron composites have been synthesized, denoted as 1:9 Mn-Co1-xS-NC@NC, 1:5 Mn-Co1-xS-NC@NC, 1:1 Mn-Co1-xS-NC@NC, and Co1-xS-NC@NC. These materials, inheriting the polyhedral shape and a novel cavity structure from their precursors, exhibit enhanced lithium polysulfide adsorption and catalytic activity due to the introduction of Mn heteroatoms and cobalt vacancies. The resultant S@1:9 Mn-Co1-xS-NC@NC cathode excels in electrochemical performance, delivering an initial discharge capacity of 999.37 mA h g−1 at 1 C, and sustaining 715.65 mA h g−1 over 100 cycles. Notably, at an elevated sulfur loading of 3.05 mg cm−2 (E/S, 14.5 uL g−1), the cathode retains an areal capacity of 3.24 cmmA h cm−2 (corresponding specific capacity of 1067.59 mA h g−1) after 61 cycles at 0.2 C. The synergistic effect of manganese dopants and cobalt vacancies confers superior adsorptive and catalytic properties, presenting a promising avenue for the development of sulfur host materials with tailored morphologies and defect-rich structures.

3D Porous Gel from the Orthogonal-junction of Nanosheet Photosensitizers with Efficient and Selective Photosensitization

Photocatalysis waste decomposition is a promising candidate for efficient cleaning of volatile organic compounds (VOCs) with enhanced safety because of the self-degradation of toxic compounds by reactive oxygen species (ROS) under light irradiation. However, the complete removal of pollutants remains challenging due to the inert characteristics of their inactivity in the presence of electrophilic ROS. Herein, a new strategy for efficient degradation of inert VOCs such as benzaldehyde has been proposed, basing on the synergism of selective adsorption and chemical activation by the construction of 3D porous gel through an orthogonal-junction of nanosheet-shaped photosensitizers. The key to the success of the combination is the use of hierarchically assembled hydrogen bonded laminates (HBLs) as gelation scaffolds. The backbone could integrate organic photosensitizers (PSs) into robust gel skeleton with enhanced ROS generation, which promotes the photocatalytic degradation. Especially, the backbone is able to directionally recognize glue clusters by hydrogen bonding to result in orthogonal 3D gel, giving remarkable selective adsorption for inert aromatic aldehydes. The synergistic integration of chemical activation and selective entrapment gives rise to unusual rapid photo-degradation for carbonyl compounds, resulting in efficient removal of inert pollutants from the environment without any adverse effect.

Adsorption, photocatalysis, and sonocatalytic activities of LaFeO3/methylcellulose/multi-walled carbon nanotubes-NiCu2O4/Zn for removal of organic pollutant: preparation, main factor, and mechanism

The primary objective of this study was to create and analyze a new type of LaFeO3/methylcellulose/multi-walled carbon nanotubes-NiCu2O4/Zn nanocomposite, called LFO/MC/MWCNT-NCO/Z, which has multiple functions. Structural investigation using field emission scanning electron microscopy showed that the nanoparticles (40–50 nm) were evenly distributed throughout the nanocomposite, suggesting that they were successfully incorporated without any clumping. FTIR research verified the existence of functional groups that facilitate electrostatic interactions with contaminants, hence strengthening catalytic performance and improving adsorption efficiency. The BET analysis revealed a significantly high specific surface area of 72.61 m2/g, which greatly enhances its ability to adsorb substances. The nanocomposite demonstrated high removal efficiency in adsorption (74.55%), photocatalysis (68.19%), and sonocatalysis (91.22%) procedures, highlighting its potential for effectively removing bisphenol A as organic pollutants. The synthesized LFO/MC/MWCNT-NCO/Z nanocomposite shows great potential in effectively eliminating organic contaminants from water solutions. This offers a sustainable way to address water pollution and protect human health and the environment.

Effects of in vitro simulated digestion and fecal fermentation on the structure and regulating the glucose and lipid activity of a polysaccharide from Mori Folium

Mori folium, as a homologous drug-food, has hypoglycemic and lipid-lowering activity. Polysaccharides are the main bioactive ingredient of the Mori folium that exhibit diverse biological activities. In this study, a homogeneous polysaccharide (MP4) was purified and characterized from Mori folium. The changes of MP4 affected by saliva, simulated gastrointestinal juice, and human fecal fermentation, including physicochemical property or its bioactivity, were systematically investigated. Meanwhile, the influence of fermentation on the bioactivity were evaluated. The results showed that the backbone of MP4 is mainly composed of →4)-α-D-GalpA-(1→ residues. The molecular weight, the levels of reducing sugar content and free monosaccharides of MP4 exhibited no significant differences indicating that gastrointestinal digestion has a minimal effect on the physicochemical characteristics of MP4. However, during in vitro gut microbiota fermentation, MP4 are significantly degraded and utilized by gut microbiota, showing increased the production of short-chain fatty acids, notably acetic acid and propionic acid. The relative abundance of beneficial bacteria such as Bacteroidetes and Actinobacteria were significantly increased, whereas the levels of pathogenic bacteria such as Fusobacteria and Megamonas were significantly decreased, which changed the composition of the gut microbiota. The Firmicutes/Bacteroides ratio was also decreased significantly. Interestingly, after in vitro fermentation, the α-glucosidase inhibitory activity was increased, the lipase inhibitory activity and cholesterol adsorption activity was decreased. Correlation analysis showed that the relative abundance of some bacteria was significantly correlated with the bioactivities. These results provide a basis for the development of Mori folium polysaccharides as functional probiotic products.

Acid–Base Properties and Adsorption Activity of Iron-Containing Composites in the Photocatalytic Degradation of Organic Pollutants

Acid–Base Properties and Adsorption Activity of Iron-Containing Composites in the Photocatalytic Degradation of Organic Pollutants

Study on Ce-MOF-derived oxides as morphology-tunable catalyst supports for dry reforming of methane

Dry reforming of methane (DRM) using CH4 and CO2 as feedstocks to catalytically produce high-value synthesis gas products has great application prospects. However, as a high-temperature heterogeneous catalytic reaction, the challenge lies in preparing efficient and stable catalysts for long-term operation. To enhance the catalytic performance by optimizing support, this study proposed regulating the catalyst structure and properties using Ce-based metal-organic framework (MOF) derivatives. Compared with the conventional Ni/CeO2, Ni/CeO2-MOF catalysts performed better in DRM. Especially, Ni/CeO2-UiO-66 demonstrated significant improvement in both catalytic activity and stability. It was also noticed that the Ni/CeO2-MOF catalysts had a potential benefit in limiting the conversion of carbon species to inactive forms given the relatively lower carbon gasification temperatures at their surfaces. The advantage of Ni/CeO2-MOF catalysts was attributed to their better void structure and reduction characteristics, as well as higher oxygen vacancy concentration and improved CO2 adsorption activation capability after pre-activation. This study revealed that MOF-derived supports had distinctive structural characteristics, which were manifested as an important component in high-temperature catalyst systems.

Biogenic Syntheses of AgNPs With Leaf Extract Abution indicum and Its Application for Antimicrobial and Photocatalytic Activity

ABSTRACTThe biogenic synthesis of silver nanoparticles (AgNPs) with leaf extract Abution indicum was done, and those were characterized by ultraviolet–visible spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), powder X‐ray diffraction (PXRD), field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM) with energy‐dispersive X‐ray (EDX) spectroscopy. The analysis by UV–vis spectroscopy showed a peak of 450 nm, and DLS and zeta potential were utilized to determine the size distribution of the biosynthesized Abution indicum–AgNPs (AI‐AgNPs) with a size range of 24–37 nm, and the X‐ray diffraction peak 38.096o was used to confirm that the crystalline structure of AI‐AgNPs. Furthermore, the antipathogenic effect of synthesized AgNPs and standard antibiotic (Ciprofloxacin) as studied the positive control in different types of bacterial pathogens likes Staphylococcus aureus and Escherichia Coli, with the zone of inhibition values of 9 mm. The synthesized AgNPs displayed excellent photocatalytic activity against reactive blue under sunlight than a UV light irradiation, and maximum degradation of 43% was achieved with 66 min of reaction time. In view of promising activity, the AgNPs could be used photocatalyst for the degradation of dyes in wastewater, and pomegranate leaf extract can be applied as eco‐benign and cost‐effective approach for AgNPs synthesis. Hence, the current findings suggest that Abutilon indicum is a valuable source for tailoring the potential of AgNPs toward various enhanced biological, photocatalytic, and adsorption activities. Consequently, the plant biological molecule‐mediated synthesized AI‐AgNPs could be excellent contenders for future therapeutic applications.

Synthesis of composites from coal gasification slag by acid leaching and NaOH activation for efficient adsorption of methylene blue

This study successfully developed a carbon-silicon composite material (C-Si@GS) by acid leaching (HCl) and alkali activation (NaOH) treatments from solid waste CGS and applied to the adsorption of methylene blue (MB). The effects of material dosage, pH, contact time, initial concentration and co-existing ions on the removal of MB were investigated. The results revealed C-Si@GS had good adsorption performance at different pH and cations, suggesting that the material had stable properties. The adsorption of MB by C-Si@GS reached the equilibrium within 12 h, and the removal rate was up to 99 %. The maximum adsorption capacity of C-Si@GS was 456.8 mg/g calculated by Langmuir model (C0 (MB) = 120 mg/L, pH=7 ± 0.2, dosage = 0.6 g/L, and T=298 K). The adsorption process is consistent with Pseudo-secondary and Freundlich models, suggesting that both physical and chemical adsorption processes coexist. Adsorption mechanisms are mainly van der Waals forces, hydrogen bonding, electrostatic attraction and π-π bond interaction, as analyzed by XPS and FT-IR. The composites were regenerated using HCl as desorption agent and the removal rate was about 50 % after 3 cycles. The results illustrated that C-Si@GS can serve as an effective adsorbent for removing MB.

Effect of solvothermal reaction time on adsorption and photocatalytic activity of spinel ZnFe2O4 nanoparticles

The present investigation explored the impact of solvothermal reaction time on the adsorption properties of synthesized spinel ZnFe2O4 Nanoparticles (ZF NPs) and their photocatalytic activity for the degradation of congo red (CR) dye. The structure, morphology and chemical composition is identified for the synthesized ZF NPs. The reaction times for the solvothermal synthesis of ZF NPs were investigated at time intervals of 6 hrs and 18 hrs which are denoted as ZF-6 h and ZF-18 h respectively. The XRD confirms the formation of spinel-type ZF-6 h and ZF-18 h with crystallite size of 5.50 nm and 8.36 nm for ZF-6 h and ZF-18 h respectively. The FESEM image of ZF-6 h exhibits microspheres, whereas in ZF-18 h NPs, the microspheres undergoes deformation. TEM analysis of ZF-6 h revealed that the microspheres were consists of 8–10 nm size ZF-NPs. Raman spectroscopy and XPS studies indicates, the reaction time influence the occupancy with 64 % and 32 % of inversion of Zn2+ cations from tetrahedral to octahedral sites in ZF-6 h and ZF-18 h, respectively. The surface area of mesoporous ZF-6 h and ZF-18 h are 138.29 m2/g and 128.41 m2/g respectively as confirmed using BET and BJH techniques. The CR dye adsorption capacity of 123.73 mg/g for ZF-6 h is higher compared to ZF-18 h (99.93 mg/g). The maximum dye removal efficiency evaluated for ZF-6 h NPs and ZF-18 h NPs was 87.33 % and 73.09 % respectively upon exposure of natural sunlight. The recyclability study identifies that ZF-6 h NPs remain stable for three degradation cycles. These results indicate that reaction time in solvothermal synthesis is sensitive to the morphology and physicochemical properties of ZF NPs. The enhanced performance of such ZF NPs is attributed to the synergistic effect of adsorption followed by photocatalytic (photo-Fenton) degradation of dyes.

Gold supported on Bi2MoO6 based on oxygen vacancy structure: Enhanced adsorption activation for efficient photocatalytic selective oxidation of benzyl alcohol

In this work, ethylene glycol was used as a mild reducing agent to prepare Bi2MoO6 support with oxygen vacancies. By introducing Au active species, an Au/BMO-Ov (Bi2MoO6 support with oxygen vacancies) photocatalyst was synthesized, which was co-modified with oxygen vacancies and Au NPs (nanoparticles), and significantly improved the capability of Bi2MoO6 for visible light-driven BA (benzyl alcohol) conversion. The 1 wt% Au/BMO-Ov exhibited the highest conversion (98.8 %) of BA and excellent selectivity (97.4 %) of BAD (benzaldehyde) under visible light. Oxygen vacancies have an inhibitory effect on the recombination of photogenerated carriers. Au NPs acted as both photosensitizers (LSPR effect captures light and generates electrons and holes) and active species (used as Lewis acids). The results of photoelectrochemistry (PEC) tests confirmed that the synergistic interaction of Au and oxygen vacancies enhanced the photoactivity of bismuth molybdate. Meanwhile, density functional theory (DFT) calculations indicated that oxygen vacancies and Au synergistically reduced the bandgap energy of Bi2MoO6 and enhanced the adsorption of BA. Au served as the Lewis acid site for adsorption of BA, and improved the reactivity of light-driven BA conversion. The corresponding mechanism was proposed based on the experimental results and DFT calculations.

Active and stable Ni-Cr oxide catalysts for oxidative dehydrogenation of ethane using CO2: Carbon cycle-assisted oxygen cycle

The CO2-assisted oxidative dehydrogenation of ethane (CO2-ODHE) is known as an ecologically beneficial process for ethylene generation and CO2 utilization. However, the quick deactivation of traditional Cr-based catalysts remains a considerable challenge. Herein, we report that a 1Ni1CrOx/ZrO2 catalyst could be high active and stable for the CO2-ODHE reaction; it showed CO2 conversion of 15.4 % and kept stable for 38 h at 600 °C, while the productivity of ethylene approached 325 μmol·min−1·gcat−1. Kinetic evaluations found a low apparent activation energy of 87.2 kJ/mol on the 1Ni1CrOx/ZrO2 catalyst. Surface Cr6+ and oxygen species were enriched to form Cr2O72− with the introduction of NiO. In addition, NiO improved the surface alkalinity and the affinity for oxygen, promoting the strong adsorption and easy activation of CO2. Importantly, Niδ+ species catalyzed the reaction between CO2 and surface-deposited carbon by redox cycling (carbon cycle), promoting Mars-van Krevelen-type carbon elimination and Cr6+ regeneration. The carbon cycle-assisted oxygen cycle on the Ni-Cr oxide catalysts could obviously enhance the carbon resistance and stable ethylene production, demonstrating potential application of Cr-based catalysts for CO2-ODHE reaction.

Catalytic performance of Cs-V-based non-noble soot oxidation catalyst used for DPF and its enhancement by cerium addition

Non-noble metal catalysts have great potential for controlling soot emissions due to their effective oxidation properties and low cost. This study investigated the characteristics of Cs-V-based non-noble metal soot catalyst and Ce doping enhancement effect through comprehensive characterization of physicochemical properties, catalytic activity evaluation, and density functional theory (DFT) theoretical calculations. The results demonstrate that Ce doping improves the degree of surface particle aggregation and the spatial distribution morphology of Cs-V-based catalyst, with a 36.7 % increase in the specific surface area. Additionally, Ce doping enhances the probability of oxygen adsorption and dissociation activation on the Cs-V-based catalyst, accelerating the soot-oxidation process, improving the soot-oxidation activity, with a decrease in the characteristic temperature T10 (temperature at 10 % conversion rate of soot) from 349.7 ℃ to 281.1 ℃, and decreases the activation energy for soot-oxidation to 5.8 kJ/mol. DFT calculations reveal that Ce doping strengthens the pulling effect of interatomic chemical bonds, facilitating the removal of oxygen atoms and dissociated reactive oxygen (Oasd), resulting in an increase in the adsorption energy of C4 molecules and a shorter bond length between C4 molecules and the catalytic surface, facilitating the desorption of post-oxidation soot products.

Effect of surface carbon of iron carbide on Fischer-Tropsch synthesis: A density functional theory study

The surface iron of iron carbide has been identified as active in Fischer-Tropsch synthesis (FTS), but the effect of surface carbon remains a topic of debate. Herein, to clarify the effect of surface carbon of iron carbide on FTS, we conducted a density functional theory (DFT) study on CO adsorption, H2 activation and CO hydrogenation over ε-Fe2C and θ-Fe3C. Compared to Fe3C(111), the Fe2C(111) facet exhibits more low-coordinated carbon, benefiting for CO adsorption and H2 activation. Because of the low-coordinated carbon, the Fe2C(111) is more active for FTS than Fe3C(111), not only through the formation of CH2 species with H atoms, but also through the direct C–C coupling for the carbon chain growth. The consumed carbon on Fe2C(111) can be recovered timely by absorption and direct dissociation of CO, ensuring the sustainability of the carbon chain growth. This work contributes to a comprehensive understanding of the FTS mechanism over iron carbide surface.

M/BiOCl-(M=Pt, Pd, and Au) Boosted Selective Photocatalytic CO2 Reduction to C2 Hydrocarbons via *CHO Intermediate Manipulation.

Selective CO2 photoreduction to C2 hydrocarbons is significant but limited by the inadequate adsorption strength of the reaction intermediates and low efficiency of proton transfer. Herein, an ameliorative *CO adsorption and H2O activation strategy is realized via decorating bismuth oxychloride (BiOCl) nanostructures with different metal (Pt, Pd, and Au) species. Experimental and theoretical calculation results reveal that distinct *CO binding energies and *H acquisition abilities of the metal cocatalysts mediate the CO2 reduction activity and hydrocarbon selectivity. The relatively moderate *CO adsorption and *H supply over Pd/BiOCl endows it with the lowest free energy to generate *CHO, leading to its highest activity of hydrocarbon production. Specifically, the Pt cocatalyst can efficiently participate in H2O dissociation to deliver more *H for facilitating the protonation of the *CHO and *CHOH, thereby favoring CH4 production with 76.51% selectivity. A lower *H supply over Pd/BiOCl and Au/BiOCl results in a large energy barrier for *CHO or *CHOH protonation and thus a more thermodynamically favored OC─CHO coupling pathway, which endows them with vastly increased C2 hydrocarbon selectivity of 81.21% and 92.81%, respectively. The understanding of efficient C2 hydrocarbon production in this study sheds light on how materials can be engineered for photocatalytic CO2 reduction.

Mechanical behavior and biological activity performance of Li+/Ca2+@Li+/K+ ion-exchanged lithium disilicate glass-ceramics

Lithium disilicate (LD) glass-ceramics used for bone repair need to have good mechanical properties and biological activity. Ion-exchange can lead a significant surficial strengthening and bioactivity of LD glass-ceramics. In this work, LD glass-ceramics were Li+/Ca2+@Li+/K+ exchanged in a mixed salt bath of 30 % Ca(NO3)2 + 70 % KNO3 (in mol %) at 400 °C for 16 h, 32 h and 64 h respectively. LD glass-ceramics were significantly strengthened after Li+/Ca2+@Li+/K+ exchange. However, due to the shallow depth of the ion-exchange layer and stress relaxation, the strengthening effect deteriorated with the prolongation of the ion-exchange time. The Li+/Ca2+@Li+/K+ exchanged LD glass-ceramics could be conducive to the formation of the hydroxyapatite (HA) after soaking in the simulated body fluid (SBF). Moreover, the protein adsorption, cytotoxicity, cell adhesion, osteoblast proliferation and alkaline phosphatase (ALP) activity expression of Li+/Ca2+@Li+/K+ exchanged LD glass-ceramics were investigated. Ca2+ release might promote the bioactivity of ion-exchanged LD glass-ceramics. Therefore, Li+/Ca2+@Li+/K+ exchange can improve the mechanical properties and bioactivity of LD glass-ceramics, which has important significance for its application in orthopedic reconstruction.