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Soil microbial flora constitutes a highly diverse and complex microbiome on Earth, often challenging to cultivation, with unclear metabolic mechanisms in situ. Here, we present a pioneering concept for the in situ construction of functional microbial consortia (FMCs) and introduce an innovative method for creating FMCs by utilizing phenanthrene as a model compound to elucidate their in situ biodegradation mechanisms. Our methodology involves single-cell identification, sorting, and culture of functional microorganisms, resulting in the formation of a precise in situ FMC. Through Raman-activated cell sorting-stable-isotope probing, we identified and isolated phenanthrene-degrading bacterial cells from Achromobacter sp. and Pseudomonas sp., achieving precise and controllable in situ consortia based on genome-guided cultivation. Our in situ FMC outperformed conventionally designed functional flora when tested in real soil, indicating its superior phenanthrene degradation capacity. We revealed that microorganisms with high degradation efficiency isolated through conventional methods may exhibit pollutant tolerance but lack actual degradation ability in natural environments. This finding highlights the potential to construct FMCs based on thorough elucidation of in situ functional degraders, thereby achieving sustained and efficient pollutant degradation. Single-cell sequencing linked degraders with their genes and metabolic pathways, providing insights regarding the construction of in situ FMCs. The consortium in situ comprising microorganisms with diverse phenanthrene metabolic pathways might offer distinct advantages for enhancing phenanthrene degradation efficiency, such as the division of labour and cooperation or communication among microbial species. Our approach underscores the importance of in situ, single-cell precision identification, isolation, and cultivation for comprehensive bacterial functional analysis and resource exploration, which can extend to investigate MFCs in archaea and fungi, clarifying FMC construction methods for element recycling and pollutant transformation in complex real-world ecosystems.
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Biodegradação Ambiental , Marcação por Isótopo , Consórcios Microbianos , Fenantrenos , Pseudomonas , Análise de Célula Única , Microbiologia do Solo , Fenantrenos/metabolismo , Marcação por Isótopo/métodos , Análise de Célula Única/métodos , Pseudomonas/metabolismo , Pseudomonas/genética , Achromobacter/metabolismo , Achromobacter/genética , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Poluentes do Solo/metabolismo , Bactérias/metabolismo , Bactérias/genética , Bactérias/classificaçãoRESUMO
A considerable efficiency gap exists between large-area perovskite solar modules and small-area perovskite solar cells. The control of forming uniform and large-area film and perovskite crystallization is still the main obstacle restricting the efficiency of PSMs. In this work, we adopted a solid-liquid two-step film formation technique, which involved the evaporation of a lead iodide film and blade coating of an organic ammonium halide solution to prepare perovskite films. This method possesses the advantages of integrating vapor deposition and solution methods, which could apply to substrates with different roughness and avoid using toxic solvents to achieve a more uniform, large-area perovskite film. Furthermore, modification of the NiOx/perovskite buried interface and introduction of Urea additives were utilized to reduce interface recombination and regulate perovskite crystallization. As a result, a large-area perovskite film possessing larger grains, fewer pinholes, and reduced defects could be achieved. The inverted PSM with an active area of 61.56 cm2 (10 × 10 cm2 substrate) achieved a champion power conversion efficiency of 20.56% and significantly improved stability. This method suggests an innovative approach to resolving the uniformity issue associated with large-area film fabrication.
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Fungal-bacterial consortia enhance organic pollutant removal, but the underlying mechanisms are unclear. We used stable isotope probing (SIP) to explore the mechanism of bioaugmentation involved in polycyclic aromatic hydrocarbon (PAH) biodegradation in petroleum-contaminated soil by introducing the indigenous fungal strain Aspergillus sp. LJD-29 and the bacterial strain Pseudomonas XH-1. While each strain alone increased phenanthrene (PHE) degradation, the simultaneous addition of both strains showed no significant enhancement compared to treatment with XH-1 alone. Nonetheless, the assimilation effect of microorganisms on PHE was significantly enhanced. SIP revealed a role of XH-1 in PHE degradation, while the absence of LJD-29 in 13C-DNA indicated a supporting role. The correlations between fungal abundance, degradation efficiency, and soil extracellular enzyme activity indicated that LJD-29, while not directly involved in PHE assimilation, played a crucial role in the breakdown of PHE through extracellular enzymes, facilitating the assimilation of metabolites by bacteria. This observation was substantiated by the results of metabolite analysis. Furthermore, the combination of fungus and bacterium significantly influenced the diversity of PHE degraders. Taken together, this study highlighted the synergistic effects of fungi and bacteria in PAH degradation, revealed a new fungal-bacterial bioaugmentation mechanism and diversity of PAH-degrading microorganisms, and provided insights for in situ bioremediation of PAH-contaminated soil.IMPORTANCEThis study was performed to explore the mechanism of bioaugmentation by a fungal-bacterial consortium for phenanthrene (PHE) degradation in petroleum-contaminated soil. Using the indigenous fungal strain Aspergillus sp. LJD-29 and bacterial strain Pseudomonas XH-1, we performed stable isotope probing (SIP) to trace active PHE-degrading microorganisms. While inoculation of either organism alone significantly enhanced PHE degradation, the simultaneous addition of both strains revealed complex interactions. The efficiency plateaued, highlighting the nuanced microbial interactions. SIP identified XH-1 as the primary contributor to in situ PHE degradation, in contrast to the limited role of LJD-29. Correlations between fungal abundance, degradation efficiency, and extracellular enzyme activity underscored the pivotal role of LJD-29 in enzymatically facilitating PHE breakdown and enriching bacterial assimilation. Metabolite analysis validated this synergy, unveiling distinct biodegradation mechanisms. Furthermore, this fungal-bacterial alliance significantly impacted PHE-degrading microorganism diversity. These findings advance our understanding of fungal-bacterial bioaugmentation and microorganism diversity in polycyclic aromatic hydrocarbon (PAH) degradation as well as providing insights for theoretical guidance in the in situ bioremediation of PAH-contaminated soil.
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Aspergillus , Biodegradação Ambiental , Consórcios Microbianos , Fenantrenos , Microbiologia do Solo , Poluentes do Solo , Fenantrenos/metabolismo , Poluentes do Solo/metabolismo , Aspergillus/metabolismo , Pseudomonas/metabolismo , Pseudomonas/genética , Bactérias/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Fungos/metabolismo , Fungos/genética , Fungos/classificaçãoRESUMO
Future sustainability visions include clean, renewable energy from hydrogen, which can be produced, among other ways, by biomass steam gasification. This study explores strategies addressing the limitations in steam co-gasification of herbaceous biomass, using Monster-TUAT1 rice straw, a genetically modified rice plant with a taller and bigger stalk developed by Tokyo University of Agriculture and Technology (TUAT), and Giant Miscanthus, a promising energy crop, as the feedstock. Firstly, compared with the typical rice straw, the Monster TUAT1 demonstrated superior steam gasification performance with a 1.75 times higher hydrogen gas yield and 27.0 % less tar generation. With a focus on overcoming the challenges posed by high silica content in the Monster TUAT1, co-gasification of it with an energy crop of Giant Miscanthus was performed. However, even under the optimum operation condition (750 °C, steam flowrate: 0.15 g/min), the hydrogen gas yield was only 29.3 mmol/g-C with a tar yield of 27.6 %wt. and a carbon conversion efficiency of 45.9 %, which is deemed unsatisfactory for hydrogen production. Thus, strategies for enhancement were proposed, including the incorporation seaweed biochar with high alkali and alkaline earth species, calcined scallop shell powder, and alkali metal salt into the gasifier. Consequently, the introduction of 10 %wt. of calcined scallop shell resulted in an increase in H2 yield to 37.0 mmol/g-C and 24.3 % CO2 reduction. The addition of alkali metal salt led to 43.9 % increase of H2 product with a 15 %wt. tar yield. The most significant improvement occurred with the introduction of seaweed biochar at 50 %wt., increasing of the hydrogen gas yield to 62.0 mmol/g-C with 86 % of carbon conversion efficiency and tar reduction to 5.5 %. These findings demonstrate the viability of utilizing herbaceous biomass such as rice straw in conjunction with the strategic solutions of co-gasification to overcome constraints in improving hydrogen production.
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Biomassa , Hidrogênio , Oryza , Vapor , Oryza/genética , Carvão VegetalRESUMO
A new green pathway of in situ electro-leaching coupled with electrochemically switched ion exchange (EL-ESIX) technology was developed for the separation and recovery of valuable metal ions from waste lithium batteries. By using the in situ electro-leaching, the leaching rates of Li+ and Co2+ from the prepared LiCoO2 film electrodes reached 100 % and 93.30 %, respectively, under the combined effect of the acidic microenvironment formed by the anodic electrolytic water and electrostatic repulsion. Subsequently, the Li+ in the electrolyte was further extracted by an electrochemically switched ion exchange (ESIX) process using LiMn2O4 as the film electrode, and Li+ was further enriched in the eluate by a cyclic adsorption and desorption process. The results indicate that the in situ electro-leaching has significant advantages over powder leaching, and for the recycling of waste lithium batteries, the final lithium recovery rate reached 94.51 % by using this in situ EL-ESIX technology.
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Lítio , Metais , Troca Iônica , Reciclagem/métodos , Fontes de Energia Elétrica , Íons , EletrodosRESUMO
In practical engineering, whilst estimating the jacking force of rectangular pipe jacking using an empirical formula, the results obtained from said formula deviate from reality and manifest inadequate engineering guidance. The equations governing the applied force during the installation of rectangular pipe jacking have been derived for various contact states involving the interaction between the pipe, slurry, and soil. The distinct stress conditions in the pipe jacking process as well as the shear-friction mechanism between the pipe and the surrounding soil have been taken into account. The displacement control method is introduced to simulate the pipe-slurry-soil contact friction during the pipe jacking process in FLAC3D. Additionally, the pipe jacking behavior, pipe-slurry-soil contact frictional force, and variation law of the jacking force are also simulated. Mutual verification was carried out using the results obtained from field monitoring, numerical and theoretical. The findings are as follows: the established equations for calculating pipe jacking force are highly applicable across various conditions of pipe-slurry-soil contact, and the outcomes derived from theoretical formulas align remarkably well with those obtained through field monitoring and numerical simulation. During the jacking process, the sidewalls exhibit initial partial sliding followed by a complete movement as the jacking force intensifies and subsequently diminishes, eventually attaining stability during the behavior adjustment phase. Moreover, the bottom pipe-soil contact is the most common situation in actual construction.
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Ultra-high energy density battery-type materials are promising candidates for supercapacitors (SCs); however, slow ion kinetics and significant volume expansion remain major barriers to their practical applications. To address these issues, hierarchical lattice distorted α-/γ-MnS@Cox Sy core-shell heterostructure constrained in the sulphur (S), nitrogen (N) co-doped carbon (C) metal-organic frameworks (MOFs) derived nanosheets (α-/γ-MnS@Cox Sy @N, SC) have been developed. The coordination bonding among Cox Sy , and α-/γ-MnS nanoparticles at the interfaces and the π-π stacking interactions developed across α-/γ-MnS@Cox Sy and N, SC restrict volume expansion during cycling. Furthermore, the porous lattice distorted heteroatom-enriched nanosheets contain a sufficient number of active sites to allow for efficient electron transportation. Density functional theory (DFT) confirms the significant change in electronic states caused by heteroatom doping and the formation of core-shell structures, which provide more accessible species with excellent interlayer and interparticle conductivity, resulting in increased electrical conductivity. . The α-/γ-MnS@Cox Sy @N, SC electrode exhibits an excellent specific capacity of 277 mA hg-1 and cycling stability over 23 600 cycles. A quasi-solid-state flexible extrinsic pseudocapacitor (QFEPs) assembled using layer-by-layer deposited multi-walled carbon nanotube/Ti3 C2 TX nanocomposite negative electrode. QFEPs deliver specific energy of 64.8 Wh kg-1 (1.62 mWh cm-3 ) at a power of 933 W kg-1 and 92% capacitance retention over 5000 cycles.
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Catalytic performance can be greatly enhanced by rational modulation of the surface state. In this study, reasonable adjustment of the surface states around the Fermi level (EF ) of molybdenum carbide (MoC) (α phase) via a Pt-N dual-doping process to fabricate an electrocatalyst named as Pt-N-MoC is performed to promote hydrogen evolution reaction (HER) performance over the MoC surface. Systematically experimental and theoretical analyses demonstrate that the synergistic tuning of Pt and N can cause the delocalization of surface states, with an increase in the density of surface states near the EF . This is beneficial for accumulating and transferring electrons between the catalyst surface and adsorbent, resulting in a positively linear correlation between the density of surface states near the EF and the HER activity. Moreover, the catalytic performance is further enhanced by artificially fabricating a Pt-N-MoC catalyst that has a unique hierarchical structure composed of MoC nanoparticles (0D), nanosheets (2D), and microrods (3D). As expected, the obtained Pt-N-MoC electrocatalyst exhibits superb HER activity with an extremely low overpotential of 39 mV@10 mA cm-2 as well as superb stability (over 24 d) in an alkaline solution. This work highlights a novel strategy to develop efficient electrocatalysts via adjusting their surface states.
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Creating electrocatalysts with high activity and stability to meet the needs of highly effective seawater splitting is of great importance to achieve the goal of hydrogen production from abundant seawater source, which however is still challenging owing to sluggish oxygen evolution reaction (OER) dynamics and the existed competitive chloride evolution reaction. Herein, high-entropy (NiFeCoV)S2 porous nanosheets are uniformly fabricated on Ni foam via a hydrothermal reaction process with a sequential sulfurization step for alkaline water/seawater electrolysis. The obtained rough and porous nanosheets provide large active surface area and exposed more active sites, which can facilitate mass transfer and are conducive to the improvement of the catalytic performance. Combined with the strong synergistic electron modulation effect of multi elements in (NiFeCoV)S2, the as-fabricated catalyst exhibits low OER overpotentials of 220 and 299 mV at 100 mA cm-2 in alkaline water and natural seawater, respectively. Besides, the catalyst can withstand a long-term durability test for more than 50 h without hypochlorite evolution, showing excellent corrosion resistance and OER selectivity. By employing the (NiFeCoV)S2 as the electrocatalyst for both anode and cathode to construct an overall water/seawater splitting electrolyzer, the required cell voltages are only 1.69 and 1.77 V to reach 100 mA cm-2 in alkaline water and natural seawater, respectively, showing a promising prospect towards the practical application for efficient water/seawater electrolysis.
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Transition-metal-based layered double hydroxides (TM-LDHs) nanosheets are promising electrocatalysts in the renewable electrochemical energy conversion system, which are regarded as alternatives to noble metal-based materials. In this review, recent advances on effective and facile strategies to rationally design TM-LDHs nanosheets as electrocatalysts, such as increasing the number of active sties, improving the utilization of active sites (atomic-scale catalysts), modulating the electron configurations, and controlling the lattice facets, are summarized and compared. Then, the utilization of these fabricated TM-LDHs nanosheets for oxygen evolution reaction, hydrogen evolution reaction, urea oxidation reaction, nitrogen reduction reaction, small molecule oxidations, and biomass derivatives upgrading is articulated through systematically discussing the corresponding fundamental design principles and reaction mechanism. Finally, the existing challenges in increasing the density of catalytically active sites and future prospects of TM-LDHs nanosheets-based electrocatalysts in each application are also commented.
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Solid-state lithium (Li) metal batteries (SSLMBs) with high-energy density and high-security are promising for energy storage application and electronic device development. However, Li dendrite generation is still one of the most important factors hindering the application of SSLMBs since interface contact degradation, dead Li accumulation, and continuous solid-electrolyte interphase (SEI) growth are always caused by Li dendrite growth, making the performances of SSLMBs deteriorate rapidly. In this study, a poly(ether block amide) (PEBA) based polymer electrolyte with lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI) as the Li salt is developed. It is found that the PEBA 2533-20% LiTFSI electrolyte possesses an ion conductivity of 3.0 × 10-5 S cm-1 at 25 °C. Especially, the Li dendrite suppression ability of SEI is greatly enhanced since it provides abundant amide groups to activate TFSI- anions and further enriches lithium fluoride (LiF) content in the SEI layer, which endows the full-cell with enhanced cyclability. As a result, the fabricated solid-state Li/PEBA 2533-20% LiTFSI/LiFePO4 (areal capacity: 0.15 mAh cm-2) battery remains 94% of its maximum capacity (127.5 mAh g-1) at a rate of 0.5C and 60 °C after 200 cycles. In particular, the full cell can cycle for almost 1000 times without short circuit. Therefore, the PEBA based electrolyte could promote the LiF enriched SEI layer into a platform to suppress the growth of Li dendrite toward SSLMBs with a long-life span.
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For the first time, a nanosheet-state CoMnx mixed oxide with multifarious active regions was synthesized by oxidation-etching assembly of metal organic framework (MOF) precursor and applied for catalytic combustion of toluene at low temperatures. The obtained optimum catalyst denoted as CoMn6 showed excellent performance, which achieved 90% conversion of 1,000 ppm toluene under a weight hourly space velocity (WHSV) of 60,000 mL/(g·h) at 219 °C. While, it also exhibited long-term stability with strong water resistance property. The characterizations of physicochemical properties indicated that the oxidation-etching assembly process built an abundant mesoporous structure in the CoMnx catalyst, which greatly increased the specific surface area (SSA). Especially, potassium permanganate as oxidant and manganese source led to uniform dispersion and assembling of cobalt atoms, which caused the generation of low-crystallinity CoMnx mixed oxide with abundant dislocations, vacancies, phase interfaces and amorphous structures, resulting in excellent low-temperature reducibility, outstanding lattice oxygen mobility and abundant active species such as Mn3+, Co3+ and adsorbed oxygen species. Density functional theory (DFT) calculations demonstrated that gaseous oxygen with the longer bond length (1.406 Å) and stronger adsorption energy (-4.443 eV) could be adsorbed and activated well on the MnCo2O4.5 (311) plane, which is beneficial for the toluene oxidation. In situ diffuse reflectance infrared spectroscopy (DRIFTS) technique was applied to track the intermediates of toluene combustion under different atmospheres, which further deduced the contributions of different active regions and oxidation mechanism over the CoMnx catalyst. The present facile strategy of oxidation-etching assembly of the MOF precursor for the creating of novel catalyst with high performance could be applied in a wide variety of materials besides VOC combustion catalysts.
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Currently, direct electrolysis of seawater-based electrolytes rather than fresh water based ones for hydrogen production is gaining more and more attentions for creating a sustainable society. However, using seawater remains more challenges owing to the existence of competitive reactions between chlorine evolution reaction (ClER) or hypochlorite generation reaction and oxygen evolution reaction (OER) and electrode erosion. In this study, a MnCo2O4 nanowire coated with NiFe-Layered Double Hydroxide (NiFe-LDH) layer (MnCo2O4@NiFe-LDH) composite electrocatalyst prepared by a simple two-step hydrothermal method was applied for the seawater electrolysis, which exhibited low overpotentials of 219 and 245 mV at a relatively high current density of 100 mA cm-2 in alkaline simulated and natural seawaters, respectively, as the anode electrocatalyst. It is found that the NiFe-LDH layer on the MnCo2O4 nanowire can serve as Cl- protective layer to hinder the ClER and anode erosion and simultaneously improve the active surface area and intrinsic properties of MnCo2O4 nanowires, allowing for faster kinetics. While, the high valence states of Mn3+, Co3+, Ni3+and Fe3+ played a vital role for OER. In addition, when it was used as the bifunctional electrocatalyst for the overall real seawater splitting, the cell composed of MnCo2O4@NiFe-LDH (-) || MnCo2O4@NiFe-LDH (+) pair only required a low voltage of 1.56 V@10 mA cm-2 and simultaneously maintained excellent stability at a high current density of 100 mA cm-2. Such an electrocatalyst could be a promising candidate for long-term seawater splitting.
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Highly conductive metal sulfides with high theoretical capacities and good conductivity have been considered as anode material alternatives for sodium-ion batteries (SIBs). Unfortunately, the unsatisfactory cycling stability and poor rate performance are usually resulted from the sluggish electrochemical kinetics and volumetric expansion in the charge/discharge process, which severely restricts their applications. Herein, trimetallic sulfides embedded into the carbon matrix with a microsphere shape (denoted as CoNiZnS/C) were successfully prepared by a facile solid sulfidation of tri-metal-organic frameworks. The nanorods-assembled microsphere structure with abundant phase boundaries of multiphase in the CoNiZnS/C would provide abundant active sites and defects for storing sodium ions and rich voids to alleviate the volumetric strains. As the anode material of SIBs, the optimum composite named as CoNiZnS/C-2 in this work demonstrated high initial Coulombic efficiency (96.52% at 0.1 A g-1), good cycling stability (maintaining 410.7 mA h g-1 at the 960th cycle at 2.0 A g-1) and excellent rate performance (477.0 mA h g-1 at 5.0 A g-1). Thus, such a multi-metal sulfide composite with special physical-chemical properties may offer a new insight to promote the electrochemical performance of sulfide-based anode materials for the SIBs.
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Contact with trace heavy metal contaminants will also lead to extremely bad health influence on human body and aquatic life. Although various adsorbents have been synthesized for the recovery of heavy metal ions, most of them shows deficient adsorption capacity, sluggish uptake rate and low selectivity. In this study, a montmorillonite/polypyrrole (MMT/PPy) film was successfully synthesized by intercalating polymers PPy into the interlayer of MMT nanosheets for selective and rapid capture of Pb2+. The electroactive film has ultrahigh uptake capacity (1373.29 mgâ g-1), which is much higher than most conventional Pb2+ adsorbents. Meanwhile, it had an extreme selectivity towards Pb2+ due to the MMT/PPy film can accurately identified Pb2+. Through characterization testing and data analysis, the selective and rapid uptake/release of Pb2+ should be realized through three ways: (1) negatively-charged laminates of MMT can generate electrostatic attraction to Pb2+; (2) -OH on the surface of MMT laminates can accurately identified and bonded with Pb2+ (M-O-Hâ M-O-Pb); (3) PPy doped by PSSn- and protic acid can rapidly catch Pb2+ (PPy+·PSSn-+Pb2++e-â PPy·PSSn-·Pb2+). Therefore, such a novel MMT/PPy nanocomposite film could has evident application prospect to remove Pb2+ from various water bodies.
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Metais Pesados , Poluentes Químicos da Água , Adsorção , Bentonita , Humanos , Troca Iônica , Íons , Chumbo , Polímeros , Pirróis , Poluentes Químicos da Água/análiseRESUMO
All-solid-state lithium-ion batteries (ASSLBs) are considered as the most promising next-generation energy storage devices. In this work, a low-cost foldable nano-Li2MnO3 integrated Poly (ethylene oxide) (PEO) based composite polymer solid electrolyte (CPSE) is prepared by simply solid-phase method. Density functional theory calculations indicate that the LMO could provide faster ion transfer channels for the migration of lithium ions between PEO chains and segments. As such, the CPSE obtained has a high ionic conductivity of 5.1 × 10-4 S cm-1 at 60 °C with a high lithium ions transference number of 0.5. The CPSE remains stable even at high temperature with no heat escaping. This could improve the safety performance of the batteries. As a result, the lithium metal battery assembled with CPSE works stably after over 200 cycles at a high rate of 0.5C, and its specific capacity is as high as 125 mAh g-1. Also, it is confirmed that this CPSE adapts to three cathode materials. The Li metal pouch battery assembled with the CPSE is foldable and has excellent mechanical properties. All these results indicate that the CPSE obtained has excellent electrochemical and outstanding safety performances, which can make it have broad commercial applications in ASSLBs.
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Activated carbon (AC) is an effective and inexpensive adsorbent material for dye removal, but it cannot always be used repeatedly. Furthermore, the adsorbed dyes with toxicity usually remain on its surface. In this study, a thermal air oxidation process was used to modify the surface of AC and decompose adsorbed methylene blue (MB). The behavior of this process on spent AC was investigated using TGA-DTA, while the degradation of MB before and after the regeneration process was analyzed using a carbon, hydrogen, nitrogen, sulfur (CHNS) analyzer. It was discovered that thermal air oxidation could promote the formation of oxygenated functional groups on AC produced from steam-activated carbon coconut shell (SACCS), which when treated at 350 °C (denoted as SACCS-350), demonstrated an adsorption capacity 2.8 times higher than the non-air-oxidized AC (SACCS). The key parameters for the MB adsorption of SACCS and SACCS-350, such as kinetics, equilibrium, and thermodynamics, were compared. Moreover, the SACCS-350 could be reused at least 3 times for the adsorption of MB. Based on these results, thermal air oxidation treatment could successfully improve the adsorption performance of AC and regenerate spent AC through a reasonable and environmentally friendly process compared to other regeneration methods.
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In this study, octahedral molecular sieve (OMS-2) is successfully delaminated by using trace holmium (Ho) via a facile redox co-precipitation route, which exhibits high performance for the total toluene oxidation at low temperature. High resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) analyses verify that abundant multi-phase interfaces and lattice dislocations are formed on the obtained delaminated OMS-2 by the Ho (Ho-OMS-2), which can induce more active oxygen species. In particular, the delaminated OMS-2 with a trace Ho amount has a high Oads/Olatt ratio with a balanced ratio of Mn3+ and Mn4+, demonstrating much higher activity (T100% of 228 °C even under 5 vol% H2O vapor over 0.5% Ho-OMS-2) than the parent OMS-2 (T100% of 261 °C) for the total toluene oxidation. Furthermore, the positive effect of the introduction of H2O on catalytic activity, especially the enhancement of the conversion of intermediates into CO2 and H2O, is verified by the in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS). Based on these results, the reaction mechanism for toluene oxidation over the OMS-2 based catalyst is proposed. It is expected to provide an effective preparation method to obtain high-performance catalysts for the VOCs oxidation at low temperatures.
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Oxygen vacancy on the heterogeneous catalyst is of great importance to the catalysis of volatile organic compound (VOC) oxidation. Herein, microwave radiation with special energy-excitation is successfully utilized for the post-processing of a series of manganese oxides (MnOx) to generate oxygen vacancies. It is found that the MnOx catalyst with 60â¯min of microwave radiation demonstrates higher activity for toluene oxidation with a T50% of 210⯰C and a T100% of 223⯰C, which is attributed to the higher concentration of oxygen vacancies derived from the rich phase interface defects resulted from the microwave radiation. Furthermore, the Mn-MW-60 catalyst possesses excellent thermal stability and water vapor tolerance even under 20â¯vol% H2O atmospheres within 60â¯h. In situ DRIFTS analysis verifies that both surface and lattice oxygen species simultaneously participate the oxidation process, and all reactions over different environments follows two different pathways. Meanwhile, it is proposed that those oxygen vacancies derived from microwave radiation could facilitate the rate-controlling step of opening the aromatic ring based on the electron back-donation, thereby leading to the increment of catalytic activity.