Active Coordinatively Unsaturated Manganese Monoxide-Containing Mesoporous Carbon Catalyst in Wet Peroxide Oxidation

Achieving high-performance electrocatalytic reduction of nitrate by N-rich carbon-encapsulated Ni-Cu bimetallic nanoparticles supported nickel foam electrode

The cathode with low-energy consumption and long-term stability is pivotal to achieve the conversion of nitrate (NO₃^-) to nitrogen (N₂) by electrocatalytic denitrification. Herein, a binder-free electrode was synthesized by directly immobilizing N-doped graphitized carbon layer-encapsulated NiCu bimetallic nanoparticles on nickel foam (NF) (NiCu@N-C/NF) and served as the cathode for electrocatalytic NO₃^- reduction. Morphological characterization indicated that Ni and Cu nanoparticles were encapsulated by the N-doped graphitized carbon layer and well-dispersed on the surface of NF. Compared with monometallic composite cathode (Cu@N-C/NF and Ni@N-C/NF), NiCu@N-C/NF exhibited better NO₃^- removal performance (98.63 %) and lower energy consumption (0.007 kW·h mmol^-1), which should be attributed to its strong adsorption ability to NO₃^- and excellent electron transfer property. Meanwhile, its electrocatalytic performance could be maintained in wide initial NO₃^- concentration (1.79-7.14 mM) and solution pH (3-11). With the assistance of electrochlorination, the N₂ selectivity of electrochemical system was up to 99.89 % in the presence of 0.028 M Cl^-. More importantly, NiCu@N-C/NF electrode displayed an ultra-high stability during ten recycling experiments. This study indicated that the binderless composite cathode NiCu@N-C/NF had great potential in electrocatalytic NO₃^- removal from wastewater.

Fe-based Fenton-like catalysts for water treatment: Preparation, characterization and modification

Fenton reaction based on hydroxyl radicals () is effective for environment remediation. Nevertheless, the conventional Fenton reaction has several disadvantages, such as working at acidic pH, producing iron-containing sludge, and the difficulty in catalysts reuse. Fenton-like reaction using solid catalysts rather than Fe²⁺ has received increasing attention. To date, Fe-based catalysts have received increasing attention due to their earth abundance, good biocompatibility, comparatively low toxicity and ready availability, it is necessary to review the current status of Fenton-like catalysts. In this review, the recent advances in Fe-based Fenton-like catalysts were systematically analyzed and summarized. Firstly, the various preparation methods were introduced, including template-free methods (precipitation, sol gel, impregnation, hydrothermal, thermal, and others) and template-based methods (hard-templating method and soft-templating method); then, the characterization techniques for Fe-based catalysts were summarized, such as X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET), SEM (scanning electron microscopy)/TEM (transmission electron microscopy)/HRTEM (high-resolution TEM), FTIR (Fourier transform infrared spectroscopy)/Raman, XPS (X-ray photoelectron spectroscopy), ⁵⁷Fe Mössbauer spectroscopy etc.; thirdly, some important conventional Fe-based catalysts were introduced, including iron oxides and oxyhydroxides, zero-valent iron (ZVI) and iron disulfide and oxychloride; fourthly, the modification strategies of Fe-based catalysts were discussed, such as microstructure controlling, introduction of support materials, construction of core-shell structure and incorporation of new metal-containing component; Finally, concluding remarks were given and the future perspectives for further study were discussed. This review will provide important information to further advance the development and application of Fe-based catalysts for water treatment.

Theranostic lyotropic liquid crystalline nanostructures for selective breast cancer imaging and therapy

Herein, we report the development of theranostic lyotropic liquid crystalline nanostructures (LCN's) loaded with unique MnO nanoparticles (MNPs) for selective cancer imaging and therapy. MNPs serves as a fluorescent agent as well as a source of manganese (Mn²⁺) and enables localized oxidative stress under the hallmarks of cancer (acidosis, high H₂O₂ level). In pursuit of synergistic amplification of Mn²⁺ antitumor activity, betulinic acid (BA) is loaded in LCN's. In this investigation, nano-architecture of LCN's phase interface is established via SAXS, Cryo-TEM and Cryo-FESEM. Intriguing in vitro studies showed that the LCN's triggered hydroxyl radical production and exhibited greater selective cytotoxicity in cancer cells, ensuring the safety of normal cells. Significant tumor ablation is realized by the 96.5 % of tumor growth inhibition index of LCN's as compared to control group. Key insights into on-site drug release, local anti-cancer response, and tumor location are gained through precise guidance of fluorescent MNPs. In addition, comprehensive assessment of the safety, pharmacokinetics and tumor distribution behavior of LCN's is performed in vivo or ex vivo. This work emphasizes the promise of modulating tumor microenvironment with smart endogenous stimuli sensitive nano systems to achieve advanced comprehensive cancer nano-theranostics without any external stimulus. STATEMENT OF SIGNIFICANCE: Effective diagnosis and treatment approaches with maximum anti-cancer activity and minimal side-effects are critical to ameliorate cancer therapy. Compared to radiation, photodynamic and photothermal therapy, the specific and selective activation of tumor microenvironmental endogenous stimuli for the logical generation of cytotoxic OH^· free radicals serves as an efficient therapeutic strategy for chemodynamic-cancer treatment. In this investigation, MnO nanoparticles fulfill two needs (fluorescence-based optical imaging and a source of Mn²⁺ based chemodynamic therapy) in one unit. This approach also ensures the safety of normal cells, as the toxic OH^· free radical activity is substantially suppressed under the mild alkaline/H₂O₂ conditions in normal cell microenvironment.

Highly Efficient Utilization of Nano-Fe(0) Embedded in Mesoporous Carbon for Activation of Peroxydisulfate

Nanoscale zerovalent iron (nZVI) particles have received much attention in environmental science and technology due to their unique electronic and chemical properties. However, the aggregation and oxidation of nZVI brings much difficulty in practical application of environmental remediation. In this study, we reported a composite nano-Fe(0)/mesoporous carbon by a chelation-assisted coassembly and carbothermal reduction strategy. Nano-Fe(0) particles with surface iron oxide (Fe₂O₃·FeO) were wrapped with graphitic layers which were uniformly dispersed in mesoporous carbon frameworks. The unique structure made the nano-Fe(0) particles stable in air for more than 20 days. It was used as a peroxydisulfate (PDS) activator for the oxidation treatment of 2,4,6-trichlorophenol (TCP). The TOF value of MCFe for TCP degradation is nearly 3 times higher than those of FeSO₄ and Fe₂O₃·FeO and nearly 2 times than that of commercial nZVI. The reactive oxygen species (ROS) including •SO₄^-, HO•, and •O₂^-, ¹O₂ are efficiently generated by PDS activation with MCFe. The PDS activation process by nano-Fe(0) particles was intrinsically induced by the ferrous ions (Fe(II)) continuously generated at the solid/aqueous interface. Namely, the nano-Fe(0) particles were highly efficiently utilized in sulfate radical-based advanced oxidation processes (SR-AOP). The porous structure also assists the absorption and transfer of TCP during the degradation process.

Enhanced Performance and Conversion Pathway for Catalytic Ozonation of Methyl Mercaptan on Single-Atom Ag Deposited Three-Dimensional Ordered Mesoporous MnO2

In this study, Ag deposited three-dimensional MnO₂ porous hollow microspheres (Ag/MnO₂ PHMSs) with high dispersion of the atom level Ag species are first prepared by a novel method of redox precipitation. Due to the highly efficient utilization of downsized Ag nanoparticles, the optimal 0.3% Ag/MnO₂ PHMSs can completely degrade 70 ppm CH₃SH within 600 s, much higher than that of MnO₂ PHMSs (79%). Additionally, the catalyst retains long-term stability and can be regenerated to its initial activity through regeneration with ethanol and HCl. The results of characterization of Ag/MnO₂ PHMSs and catalytic performance tests clearly demonstrate that the proper amount of Ag incorporation not only facilitates the chemi-adsorption but also induces more formation of vacancy oxygen (O_v) and lattice oxygen (O_L) in MnO₂ as well as Ag species as activation sites to collectively favor the catalytic ozonation of CH₃SH. Ag/MnO₂ PHMSs can efficiently transform CH₃SH into CH₃SAg/CH₃S-SCH₃ and then oxidize them into SO₄^2- and CO₂ as evidenced by in situ diffuse reflectance infrared Fourier transform spectroscopy. Meanwhile, electron paramagnetic resonance and scavenger tests indicate that •OH and ¹O₂ are the primary reactive species rather than surface atomic oxygen species contributing to CH₃SH removal over Ag/MnO₂ PHMSs. This work presents an efficient catalyst of single atom Ag incorporated MnO₂ PHMSs to control air pollution.

Fe1-xZnxS ternary solid solution as an efficient Fenton-like catalyst for ultrafast degradation of phenol

Heterogeneous Fenton-like system has been proved to be an promising alternative to Fenton system due to its easy separation. However, it's a challenge to design heterogeneous Fenton-like catalysts with high activity and great durability. Here, ternary solid solution Fe_1-xZn_xS were prepared via hydrothermal synthesis as heterogeneous Fenton-like catalysts. The Fe_0.7Zn_0.3S sample exhibited state of the art activity for yielding OH by H₂O₂ decomposition, and the ultrafast degradation of phenol was achieved in 4 min at initial acidic condition under room temperature. The phenol degradation rate constant of Fe_0.7Zn_0.3S was 99 and 70 times of ZnS and FeS, respectively. Further, we show that the unique structural configuration of iron atoms, the formation of FeS₂-pyrite with (200) plane, are responsible for the excellent activity. The intermediate products were identified by LC-MS and a possible pathway was accordingly proposed to elucidate the mechanism of phenol degradation by OH. Overall, this work provides an idea for the rational design of the relevant heterogeneous Fenton-like catalysts.

Lewis-Basic Lanthanide Metal-Organic Framework-Derived Versatile Multi-Active-Site Synergistic Catalysts for Oxygen Reduction Reaction

Oxygen reduction reaction underpins the development of the whole fuel-cell field, where there is a strong impetus to develop efficient and stable catalysts that can replace the precious metal Pt/C. Herein, a series of excellent catalysts for ORR derived from Ce/La dual lanthanide metal-organic framework with functional Lewis-basic sites were synthesized for the first time. The synergistic effect of high concentration of oxygen vacancies from La-embedded CeO₂ and Fe-N _x sites as well as porous structure endows the catalyst superior performance to Pt/C, with a half-wave potential ( E_1/2) of 0.870 V and a current density ( j) of 5.43 mA/cm². Furthermore, the catalysts are also effective for other nonelectrocatalytic reactions. It is expected that this research will contribute to synthesis of an excellent nonplatinum electrocatalyst for fuel-cell applications, and the oxygen vacancies stabilized in carbon matrix offer a method for versatile catalyst design for other reactions.

Facile Synthesis of Lanthanide (Ce, Eu, Tb, Ce/Tb, Yb/Er, Yb/Ho, and Yb/Tm)-Doped LnF3 and LnOF Porous Sub-Microspheres with Multicolor Emissions

Monodisperse YF₃ and YOF porous sub-microspheres were synthesized by using a novel sacrificing template method with amorphous Y(OH)CO₃ ⋅x H₂ O as the precursors and the template. It was found that the size and shape were well maintained, and the condensed precursor was transformed into uniform porous structures after fluoridation. By fine-tuning the feed of the fluorine source, the final product could be converted from YF₃ to YOF. A possible growth mechanism is proposed for the uniform porous YF₃ structure and the porous yolk-shell-like YOF structure. The luminescence properties showed that the as-synthesized YF₃ :Ln³⁺ (Ln=Eu, Tb, Ce, Ce/Tb, Yb/Er, Yb/Ho, and Yb/Tm) products exhibited strong multicolor emissions, which included down-/upconversion and energy-transfer processes. Additionally, YOX (X=Cl and Br) could be obtained if a different halogen source was used during calcination. However, the spheres were almost completely destroyed. Our novel synthetic route can also be extended to other lanthanide fluorides (REF₃ , RE=Gd, Lu), which may open a facile way to fabricate novel porous nanostructures.

An efficient catalytic degradation of trichloroethene in a percarbonate system catalyzed by ultra-fine heterogeneous zeolite supported zero valent iron-nickel bimetallic composite

Zeolite supported nano iron-nickel bimetallic composite (Z-nZVI-Ni) was prepared using a liquid-phase reduction process. The corresponding surface morphologies and physico-chemical properties of the Z-nZVI-Ni composite were determined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy dispersive X-ray spectra (EDS), Brunauer Emmett Teller (BET) adsorption, wide angle X-ray diffractometry (WA-XRD), and Fourier transform infrared spectroscopy (FTIR). The results indicated high dispersion of iron and nickel nano particles on the zeolite sheet with an enhanced surface area. Complete destruction of trichloroethene (TCE) and efficient removal of total organic carbon (TOC) were observed by using Z-nZVI-Ni as a heterogeneous catalyst for a Fenton-like oxidation process employing sodium percarbonate (SPC) as an oxidant. The electron spin resonance (ESR) of Z-nZVI-Ni verified the generation and intensity of hydroxyl radicals (OH•). The quantification of OH• elucidated by using p-chlorobenzoic acid, a probe indicator, confirmed the higher intensity of OH•. The transformation products were identified using GC-MS. The slow iron and nickel leaching offered higher stability and better catalytic activity of Z-nZVI-Ni, demonstrating its prospective long term applications in groundwater for TCE degradation.

Peanut-Shell-like Porous Carbon from Nitrogen-Containing Poly-N-phenylethanolamine for High-Performance Supercapacitor

An efficient soft-template method is proposed for the synthesis of peanut shell-like porous carbon as high-performance supercapacitor electrode materials. The procedure is based on the pyrolysis and chemical activation processes using N-phenylethanolamine as precursor and KOH as activation agent. In a three-electrode system, the resultant carbon material has a specific capacitance of 356 F g(-1) at 1 A g(-1) and a good stability over 1000 cycles. Besides, at a high current density of 30 A g(-1), it has a specific capacitance of 249 F g(-1) and maintains 96% after 10,000 cycles. In two-electrode cell configuration, it delivers about 21.53 Wh kg(-1) at a current density of 20 A g(-1), which is about 7 times higher than the commercial device (<3 Wh kg(-1)). Both high specific capacitance and excellent cycling stabilities guarantee its utilization in supercapacitors.

Review of iron-free Fenton-like systems for activating H2O2 in advanced oxidation processes

Iron-catalyzed hydrogen peroxide decomposition for in situ generation of hydroxyl radicals (HO(•)) has been extensively developed as advanced oxidation processes (AOPs) for environmental applications. A variety of catalytic iron species constituting metal salts (in Fe(2+) or Fe(3+) form), metal oxides (e.g., Fe2O3, Fe3O4), and zero-valent metal (Fe(0)) have been exploited for chemical (classical Fenton), photochemical (photo-Fenton) and electrochemical (electro-Fenton) degradation pathways. However, the requirement of strict acidic conditions to prevent iron precipitation still remains the bottleneck for iron-based AOPs. In this article, we present a thorough review of alternative non-iron Fenton catalysts and their reactivity towards hydrogen peroxide activation. Elements with multiple redox states (like chromium, cerium, copper, cobalt, manganese and ruthenium) all directly decompose H2O2 into HO(•) through conventional Fenton-like pathways. The in situ formation of H2O2 and decomposition into HO(•) can be also achieved using electron transfer mechanism in zero-valent aluminum/O2 system. Although these Fenton systems (except aluminum) work efficiently even at neutral pH, the H2O2 activation mechanism is very specific to the nature of the catalyst and critically depends on its composition. This review describes in detail the complex mechanisms and emphasizes on practical limitations influencing their environmental applications.

Heterogeneous Fenton-like degradation of 4-chlorophenol using iron/ordered mesoporous carbon catalyst

Ordered mesoporous carbon supported iron catalysts (Fe/OMC) were prepared by the incipient wetness impregnation method and investigated in Fenton-like degradation of 4-chlorophenol (4CP) in this work. XRD and TEM characterization showed that the iron oxides were well dispersed on the OMC support and grew bigger with the increasing calcination temperature. The catalyst prepared with a lower calcination temperature showed higher decomposition efficiency towards 4CP and H2O2, but more metals were leached. The effect of different operational parameters such as initial pH, H2O2 dosage, and reaction temperature on the catalytic activity was evaluated. The results showed that 96.1% of 4CP and 47.4% of TOC was removed after 270 min at 30°C, initial pH of 3 and 6.6 mmol/L H2O2. 88% of 4CP removal efficiency was retained after three successive runs, indicating Fe/OMC a stable catalyst for Fenton reaction. 4CP was degraded predominately by the attack of hydroxyl radical formed on the catalyst surface and in the bulk solution due to iron leaching. Based on the degradation intermediates detected by high performance liquid chromatography, possible oxidation pathways were proposed during the 4CP degradation.

Synthesis of porous upconverting luminescence α-NaYF4:Ln3+ microspheres and their potential applications as carriers

The present work reports a self-sacrificing template strategy to synthesize porous α-NaYF₄ microspheres via the reaction of as-prepared Y(OH)CO₃·H₂O@SiO₂ with NH₄F and NaNO₃ solutions.