Effect of Pd/Ce loading on the performance of Pd-Ce/γ-Al2O3 catalysts for toluene abatement

Catalytic oxidation of toluene by manganese oxides: Effect of K+ doping on oxygen vacancy

Alkali metal potassium was beneficial to the electronic regulation and structural stability of transition metal oxides. Herein, K ions were introduced into manganese oxides by different methods to improve the degradation efficiency of toluene. The results of activity experiments indicated that KMnO4-HT (HT: Hydrothermal method) exhibited outstanding low-temperature catalytic activity, and 90% conversion of toluene can be achieved at 243°C, which was 41°C and 43°C lower than that of KNO3-HT and Mn-HT, respectively. The largest specific surface area was observed on KMnO4-HT, facilitating the adsorption of toluene. The formation of cryptomelane structure over KMnO4-HT could contribute to higher content of Mn3+ and lattice oxygen (Olatt), excellent low-temperature reducibility, and high oxygen mobility, which could increase the catalytic performance. Furthermore, two distinct degradation pathways were inferred. Pathway Ⅰ (KMnO4-HT): toluene → benzyl → benzoic acid → carbonate → CO2 and H2O; Pathway ⅠⅠ (Mn-HT): toluene → benzyl alcohol → benzoic acid → phenol → maleic anhydride → CO2 and H2O. Fewer intermediates were detected on KMnO4-HT, indicating its stronger oxidation capacity of toluene, which was originated from the doping of K+ and the interaction between KOMn. More intermediates were observed on Mn-HT, which can be attributed to the weaker oxidation ability of pure Mn. The results indicated that the doping of K+ can improve the catalytic oxidation capacity of toluene, resulting in promoted degradation of intermediates during the oxidation of toluene.

Ultrathin heteroatom-doped CeO2 nanosheet assemblies for durable oxygen evolution: Oxygen vacancy engineering to trigger deprotonation

The manipulation of oxygen vacancies (OVs) in metal oxides has progressively emerged as a versatile strategy for improving their catalytic performance. In this study, we aim to enhance the oxygen evolution reaction (OER) performance of cerium oxide (CeO2) by doping heteroatoms (Fe, Co, Ni) to generate additional OVs. We systematically analyzed both the morphology and electronic structure of the obtained CeO2 catalysts. The experimental results revealed the self-assembly of two-dimensional (2D) CeO2 nanosheets, with an approximate thickness of ∼1.7 nm, into 2D nanosheet assemblies (NSAs). Moreover, the incorporation of heteroatoms into the CeO2 matrix promoted the formation of OVs, resulting in a significant enhancement of the OER performance of CeO2. Among them, the Co-doped CeO2 NSAs sample displayed the highest activity and durability, with almost negligible activity loss during extended operating periods. The roles of heteroatom doping in improving OER activity were explored by DFT calculations. The produced OVs improve the adsorption of hydroxyl groups (OH-), promote the deprotonation process, and increase more active sites. These findings suggest that doping CeO2 with heteroatoms is a promising strategy for improving electrocatalytic OER activity, with great potential for the development of clean energy technologies, including but not limited to water splitting and fuel cells.

Synthesis of xCe-MnO2 with three-dimensional ultra-thin nanosheet structure and its excellent low-temperature reducibility for toluene catalysis

A series of xCe-MnO2 (x = 0-1) catalysts were synthesized using ammonium oxalate as a precipitator via the redox precipitation method and hydrothermal synthesis method. The results indicate that 0.25Ce-MnO2 exhibited the highest catalytic activity for toluene oxidation, with the T99 of 240 °C. Characterization results from XRD, Raman, SEM, TEM, EDS-mapping, BET, and other techniques reveal that the 0.25Ce-MnO2 catalyst exhibited a three-dimensional multistage ultrathin nanosheet structure by adjusting the introduction amount of Ce, with abundant active sites, and effectively formed Ce-Mn homogeneous dispersion. The larger pore size and volume of 0.25Ce-MnO2 catalyst lead to it excellent toluene transfer ability. Furthermore, compared with MnO2, the crystal pattern of 0.25Ce-MnO2 shifted to the tetragonal cryptomelane type α-MnO2 phase and exposed more crystal planes which are beneficial to catalyze toluene. H2-TPR, O2-TPD, and XPS characterization further confirmed the strong interaction between Ce and Mn oxides, which exhibited better low-temperature reducibility and oxygen migration, along with abundant Ce3+ and Mn3+ species, where lattice oxygen played a major role. Moreover, in situ DRIFTS revealed that the 0.25Ce-MnO2 catalyst showed higher adsorption and desorption capacity for toluene than the MnO2 catalyst, and benzoate species were the key intermediates for catalytic oxidation. Additionally, benzoate and surface phenolic species were the key intermediates for catalytic oxidation of MnO2. Because 0.25Ce-MnO2 possesses better ability of converting toluene to benzoate species, it exhibits better activity.

Fabricating Robust Pt Clusters on Sn-Doped CeO2 for CO Oxidation: A Deep Insight into Support Engineering and Surface Structural Evolution

The size effect on nanoparticles, which affects the catalysis performance in a significant way, is crucial. The tuning of oxygen vacancies on metal-oxide support can help reduce the size of the particles in active clusters of Pt, thus improving catalysis performance of the supported catalyst. Herein, Ce-Sn solid solutions (CSO) with abundant oxygen vacancies have been synthesized. Activated by simple CO reduction after loading Pt species, the catalytic CO oxidation performance of Pt/CSO was significantly better than that of Pt/CeO₂ . The reasons for the elevated activity were further explored regarding ionic Pt single sites being transformed into active Pt clusters after CO reduction. Due to more exposed oxygen vacancies, much smaller Pt clusters were created on CSO (ca. 1.2 nm) than on CeO₂ (ca. 1.8 nm). Consequently, more exposed active Pt clusters significantly improved the ability to activate oxygen and directly translated to the higher catalytic oxidation performance of activated Pt/CSO catalysts in vehicle emission control applications.

Non-thermal plasma synthesis of supported Cu-Mn-Ce mixed oxide catalyst towards highly improved catalytic performance for volatile organic compound oxidation

Compared with that of the transition metal mixed oxide pellet catalyst, the catalytic activity of the supported mixed oxide catalyst was significantly reduced, which was limited in practical industrial applications. In this work, supported Cu-Mn-Ce mixed oxide catalysts were prepared by non-thermal plasma. Catalyst characterization result demonstrated that plasma treatment could promote the proportion of oxygen vacancy and enhance the adsorptive strength of VOCs on the surface of catalyst. Meanwhile, plasma treatment process exerted a slight influence on the pore structure and morphological property of the catalyst. Consequently, CMC/SiO₂-P exhibited much higher catalytic activity than CMC/SiO₂ prepared by the incipient wetness impregnation method for the catalytic oxidation of toluene and n-hexane. Among the catalysts prepared, the 15%CMC/SiO₂-P catalyst even exhibited a high catalytic activity comparable to that of the supported noble metal catalyst for the oxidation of the inert hexane. The T₉₈ of toluene and n-hexane over 15%CMC/SiO₂-P was 260 and 280°C under the conditions of VOC concentration at 1000 ppm and WHSV at 20,000 mL·g^-1·h^-1, respectively. This work provided a novel method for the preparation of the supported transition metal mixed oxide catalyst.

Hippo dictates signaling for cellular homeostasis and immune defense in Crassostrea hongkongensis hemocytes

Introduction

The Hippo signaling pathway is an evolutionarily conserved signaling cascade that plays a crucial role in regulating cell proliferation, differentiation, and apoptosis. It has been shown to be a key regulator of cell fate and cellular homeostasis in various immune processes. Despite its well-established functions in vertebrate immunity, its roles in marine invertebrate immunity remain poorly understood. Therefore, our present work provides fresh mechanistic insights into how the Hippo pathway orchestrates hemocytic functions in Crassostrea hongkongensis, with implications for studies on its major forms and modifications in animal evolution.

Method

The complete set of Hippo pathway genes, including SAV1, MOB1, LATS, YAP/TAZ, TEAD, and MST, were identified from the C. hongkongensis genome. Quantitative PCR assays were conducted to examine the mRNA expression levels of these genes in different tissues and the levels of these genes in hemocytes before and after bacterial challenges. The study also examined the crosstalk between the Hippo pathway and other immune pathways, such as the AP-1 and p53-dependent p21 signaling cascades. RNA interference was used to knock down MST and TEAD, and MST is a core orchestrator of non-canonical Hippo signaling, to investigate its impact on phagocytosis and bacterial clearance in hemocytes.

Result

The results demonstrated that members of the Hippo pathway were highly expressed in hemocytes, with their expression levels significantly increasing following bacterial challenges. Crosstalk between the Hippo pathway and other immune pathways triggered hemocytic apoptosis, which functioned similarly to the canonical Mst-Lats-Yap signaling pathway in Drosophila and mammals. Knocking down MST resulted in increased phagocytosis and boosted the efficiency of bacterial clearance in hemocytes, presumably due to mobilized antioxidant transcription by Nrf for maintaining immune homeostasis.

Discussion

This study provides novel insights into the regulatory mechanisms underlying the Hippo pathway in immune responses of C. hongkongensis hemocytes. The study highlights the importance of the Hippo pathway in maintaining immune homeostasis and orchestrating hemocytic functions in oysters. Moreover, this study demonstrates the divergence of the Hippo pathway's roles in marine invertebrate immunity from mammalian observations, indicating the need for further comparative studies across species. These findings have significant implications for future research aimed at elucidating the evolutionary trajectory and functional diversity of the Hippo signaling pathway in animal evolution.

Noble-Metal-Based Catalytic Oxidation Technology Trends for Volatile Organic Compound (VOC) Removal

Volatile organic compounds (VOCs) are toxic and are considered the most important sources for the formation of photochemical smog, secondary organic aerosols (SOAs), and ozone. These can also greatly affect the environment and human health. For this reason, VOCs are removed by applying various technologies or reused after recovery. Catalytic oxidation for VOCs removal is widely applied in the industry and is regarded as an efficient and economical method compared to other VOCs removal technologies. Currently, a large amount of VOCs are generated in industries with solvent-based processes, and the ratio of aromatic compounds is high. This paper covers recent catalytic developments in VOC combustion over noble-metal-based catalysts. In addition, this report introduces recent trends in the development of the catalytic mechanisms of VOC combustion and the deactivation of catalysts, such as coke formation, poisoning, sintering, and catalyst regeneration. Since VOC oxidation by noble metal catalysts depends on the support of and mixing catalysts, an appropriate catalyst should be used according to reaction characteristics. Moreover, noble metal catalysts are used together with non-noble metals and play a role in the activity of other catalysts. Therefore, further elucidation of their function and catalytic mechanism in VOC removal is required.

Preparation of VOC low-temperature oxidation catalysts with copper and iron binary metal oxides via hydrotalcite-like precursors

Design diagram for the removal toluene by Cu–Fe catalyst prepared from precursor hydrotalcite.

Recent progresses in the synthesis of MnO2 nanowire and its application in environmental catalysis

Nanostructured MnO₂ with various morphologies exhibits excellent performance in environmental catalysis owing to its large specific surface area, low density, and adjustable chemical properties. The one-dimensional MnO₂ nanowire has been proved to be the dominant morphology among various nanostructures, such as nanorods, nanofibers, nanoflowers, etc. The syntheses and applications of MnO₂-based nanowires also have become a research hotspot in environmental catalytic materials over the last two decades. With the continuous deepening of the research, the control of morphology and crystal facet exposure in the synthesis of MnO₂ nanowire materials have gradually matured, and the catalytic performance also has been greatly improved. Differences in the crystalline phase structure, preferably exposed crystal facets, and even the length of the MnO₂ nanowires will evidently affect the final catalytic performances. Besides, the modifications by doping or loading will also significantly affect their catalytic performances. This review carefully summarizes the synthesis strategies of MnO₂ nanowires developed in recent years as well as the influences of the phase structure, crystal facet, morphology, dopant, and loading amount on the catalytic performance. Besides, the cutting-edge applications of MnO₂ nanowires in the field of environmental catalysis, such as CO oxidation, the removal of VOCs, denitrification, etc., have been also summarized. The application of MnO₂ nanowire in environmental catalysis is still in the early exploratory stage. The gigantic gap between theoretical investigation and industrial application is still a great challenge. Compared with noble metal based traditional environmental catalytic materials, the lower cost of MnO₂ has injected new momentum and promising potential into this research field.

This review summarizes the synthesis strategies for MnO₂ nanowire and the influences of the phase structure, crystal facet, metal doping, and interface effect on its performance in various environmental catalysis processes.

Roles of Oxygen Vacancies of CeO2 and Mn-Doped CeO2 with the Same Morphology in Benzene Catalytic Oxidation

Mn-doped CeO₂ and CeO₂ with the same morphology (nanofiber and nanocube) have been synthesized through hydrothermal method. When applied to benzene oxidation, the catalytic performance of Mn-doped CeO₂ is better than that of CeO₂, due to the difference of the concentration of O vacancy. Compared to CeO₂ with the same morphology, more oxygen vacancies were generated on the surface of Mn-doped CeO₂, due to the replacement of Ce ion with Mn ion. The lattice replacement has been analyzed through XRD, Raman, electron energy loss spectroscopy and electron paramagnetic resonance technology. The formation energies of oxygen vacancy on the different exposed crystal planes such as (110) and (100) for Mn-doped CeO₂ were calculated by the density functional theory (DFT). The results show that the oxygen vacancy is easier to be formed on the (110) plane. Other factors influencing catalytic behavior have also been investigated, indicating that the surface oxygen vacancy plays a crucial role in catalytic reaction.

Efficient degradation of ciprofloxacin by magnetic γ-Fe2O3-MnO2 with oxygen vacancy in visible-light/peroxymonosulfate system

In this work, the magnetic γ-Fe₂O₃-MnO₂ bifunctional catalyst with oxygen vacancy was synthesized for peroxymonosulfate (PMS) activation under visible light. The activity of γ-Fe₂O₃-MnO₂ was investigated by ciprofloxacin (cipro) degradation. Results showed that 98.3% of cipro (50 μM) was removed within 30 min in visible-light/PMS system mediated by γ-Fe₂O₃-MnO₂ (2:1) with fine-tuned oxygen vacancy. The cipro degradation data fitted well with pseudo-first-order kinetic model with the highest kinetic constant of 0.114 min^-1. Besides, the γ-Fe₂O₃-MnO₂ exhibited stability, recyclability and practicability. High selectivity for cipro degradation was observed with coexisting anions in visible-light/γ-Fe₂O₃-MnO₂/PMS system. Furthermore, the enhanced mechanism of PMS activation under visible light with γ-Fe₂O₃-MnO₂ was proposed. The appropriate oxygen vacancy enhanced the separation of photo-induced carriers and Z scheme heterostructure maintained the highest redox potential. Accordingly, the synergistic effect of photocatalysis and PMS activation enhanced cipro degradation. Free radical and non-radical species including , h⁺, ¹O₂, •OH and co-existed in the coupled system. Impressively, this study provides a handy approach for oxygen vacancy regulation in metallic oxides composite and an easily recycled catalyst with high-activity in coupled oxidation system towards antibiotic degradation.

Highly Active PdO/Mn3 O4 /CeO2 Nanocomposites Supported on One Dimensional Halloysite Nanotubes for Photoassisted Thermal Catalytic Methane Combustion

In this work, we have successfully triggered the aqueous auto-redox reactions between reductive Ce(OH)₃ and oxidative MnO₄ ^- /Pd²⁺ ions to form PdO/Mn₃ O₄ /CeO₂ (PMC) nanocomposites. PMC could spontaneously self-assemble into compact encapsulation on the surface of halloysite nanotubes (HNTs) to form the final one dimensional HNTs supported PMCs (HPMC). It is identified that there exists strong synergistic effects among the components of PdO, Mn₃ O₄ , and CeO₂ , and hence HPMC could show excellent performance on photoassisted thermal catalytic CH₄ combustion that its light-off temperature was sharply reduced to be 180 °C under visible light irradiation. Based on detailed studies, it is found that the catalytic reaction process well follows the classic MVK mechanism, and adsorption/activation of O₂ into active oxygen species (O*) should be the rate-determining step for CH₄ conversion.

Efficient α-MnO2 with (2 1 0) facet exposed for catalytic oxidation of toluene at low temperature: A combined in-situ DRIFTS and theoretical investigation

The α-MnO₂ catalysts with (1 1 0), (2 1 0) and (3 1 0) crystal facets exposed were prepared via hydrothermal method and studied for the catalytic oxidation of toluene. Some characterization technologies and DFT theoretical calculation were combined to analyze the as-synthesized catalysts. The α-MnO₂ catalyst exposed with the (2 1 0) plane displayed best catalytic performance and attained complete toluene conversion at 140 °C. The O₂-TPD and XPS results exhibited the amount of surface lattice oxygen on α-MnO₂-210 catalyst was largest. Lower accumulation and faster disintegration of intermediates which was characterized by in-situ DRIFTS could be discovered on the surface of α-MnO₂-210 catalyst. The results of DFT calculation showed that the unique atomic arrangement of α-MnO₂-210 catalyst enhanced the charge separation and conversion, promoting the formation of active oxygen and the activation of toluene. The E_a of α-MnO₂-210 catalyst was 24.75 kJ mol^-1, lowest among the three catalysts. This work highlights the facet effects on catalytic property and provides new insight into the understanding of catalytic oxidation reaction mechanism of toluene.