Microchemical Environment Research Articles

Ru nanoparticles embedded in Ru/SiO2@N-CS for boosting hydrogen production via ammonia decomposition with robust lifespan

Ammonia decomposition for onsite hydrogen production has been regarded as an important reaction which links to efficient hydrogen storage, transport and utilization. However, it still remains challenging to develop efficient catalysts with robust stability for ammonia decomposition. Herein, an integrated strategy was employed to synthesize Ru/SiO2@N-CS via wrapping a thin layer of N-doped carbon onto the SiO2 sphere, following the anchor of Ru nanoparticles (NPs) onto the support. The obtained Ru/SiO2@N-CS (Ru loading: 1 wt%) shows a promising performance for ammonia decomposition, reaching 94.5 % at 550 °C with a gas hourly space velocity (GHSV) of 30 000 mL gcat-1h−1. The combination of the SiO2 as the core prevents the degradation of N-doped carbon layers and then enhance the durability of the catalysts, remaining stable after 50 h at evaluated temperatures. Adequate characterizations were used to illustrate the effect of microchemical environment on ammonia decomposition activity of Ru/SiO2@N-CS catalyst under different calcination atmosphere and the correlation between structure and performance.

Optimization of isolated copper species on the NH3-SCR performance over Cu/SSZ-39 modified by ammonia water

To further improve the activity of Selective Catalytic Reduction of nitrogen oxide (NOx) with Ammonia (NH3-SCR) and the hydrothermal stability at 900 °C on Cu-based small-pore zeolite catalyst, the interaction between ammonia water and Cu2+ is used to regulate the interaction between Cu2+ and Si-O-Al structures of the zeolite, and affect the migration of Cu2+ in the channels of zeolite. The characterization results show that the microchemical environment of isolated Cu2+ species is optimized, and more isolated Cu2+ species can stably exist over the surface of Cu/SSZ-39, exhibiting a strong redox property. Besides, the ability of acid sites to adsorb and activate NH3 is also enhanced, and the amount of H2O adsorbed in the pores of zeolite is reduced due to the stable surface isolated Cu2+ species, which is conducive to the stability of the catalyst after hydrothermal aging at 900 °C. When the mole ratio of ammonia and copper is 3, the NH3-SCR performance and the hydrothermal stability at 900 °C are both optimized on the modified catalyst. The temperature window that the NOx conversion is higher than 90% (ΔT90) on the unmodified catalyst is 200–475 °C, but the ΔT90 on the modified catalyst is broadened to 178–544 °C. More importantly, after hydrothermal aging at 900 °C, the ΔT90 on the modified catalyst is shifted to the higher temperature by 48 °C, with the maximum NOx conversion of 96%. This work would provide a new strategy for further optimizing Cu/SSZ-39 catalyst for deNOx emitted from diesel engines to meet higher emission standards in future.

Oxygen Vacancies Boost High‐Energy {100} Faceted TiO2 for Efficient Photocatalytic Degradation of Rhodamine B

AbstractPhotocatalytic reaction takes place on the surface of the catalyst, the crystal plane engineering which can adjust and optimize the surface atomic ordering and electronic energy band structure has been widely studied, considering the microchemical environment changes caused by defects on different surfaces, the combination of crystal plane engineering and defect engineering is expected to become a promising strategy to greatly improve the performance of photocatalysis. In this paper, we introduce 2,2’‐Bipyridyl to induce oxygen vacancy in the synthesis of highly exposed {100} faceted TiO2 nanorods, and obtain oxygen‐rich TiO2 nanomaterials. Benefit from the synergistic effect of high‐energy crystal plane and oxygen vacancy, 96.8 % Rhodamine B (10 mg ⋅ L−1) is degraded after irradiation of 30 min in T100‐VO photocatalytic system. This study provides a new strategy and inspiration for low‐cost control of semiconductor oxides and the design of efficient photocatalysts for environmental purification.

Manipulation of the electronic state of Au to boost the catalytic efficiency of Au/polyaniline by doping engineering

Polyaniline (PANI) support was doped by acids including HCl acid, 10-camphorsulfonic acid (CSA), thioglycollic acid (TA), and citric acid (CA), to modulate the environment of Au. The catalytic activities refer to the following sequence of Au/CA-PANI > Au/TA-PANI > Au/HCl-PANI ≈ Au/CSA-PANI > Au/EB-PANI toward the 4-nitrophenol (4-NP) reduction. It is found that a less positively charged Au surface can adsorb an appropriate 4-NP molecules and further increase the catalytic performance. The Au/CA-PANI with the lowest positively charged Au surface displayed the highest activity in 4-NP reduction with a reaction rate of 0.035 s−1 and a turnover frequency of 1997 h−1. The electronic state of Au likely played a decisive role for the catalytic activity differences. The readily microchemical environment tuning enabled for the accurate regulation of the electronic state of Au. This work provides a strategy for designing Au catalysts with an accurate electronic state surface.

In-situ radial pH monitoring inside the crevice of stainless steel combined with potentiometric scanning electrochemical microscopy

The development of crevice corrosion is closely related to changes in the microchemical environment in crevices. However, it is difficult to detect the microchemical information inside the crevice using conventional electrochemical techniques. To this end, a Pt/IrOx-pH ultramicroelectrode (UME) with a radius of 690 nm was developed to study the local radial pH distribution in the crevice using the potentiometric mode of SECM in situ. This pH UME showed excellent sensitivity and stability over a wide pH range between 1.0 and 13.0. The feasibility of this pH UME was demonstrated in the study of the radial pH distribution within the slit with a slit of 101.30 μm for 201 stainless steel (201- SS). The result showed that a significant radial pH difference was observed within the gap: the largest pH drop was observed at the opening from pH = 4.2 to 1.6, followed by the middle and the bottom. This result agreed well with the images of in-situ corrosion morphology seen in optical microscopy. This combination of SECM and submicron pH UME could be used to explore the mechanisms of crevice corrosion in various metals as well as the early stages of pitting corrosion.

Multi-Watt cavity for 266 nm light in vacuum

Intense coherent ultraviolet radiation is gaining increasing importance in advanced quantum technologies—from optical clocks and quantum computers to matter-wave interferometry—as well as in photochemistry, life sciences, semiconductor industry, and space applications. Since the preparation of multi-Watt light sources is still an open challenge for many ultraviolet wavelengths, resonant enhancement in a cavity is an attractive alternative. However, many experiments with atoms, molecules or nanoparticles require isolation in high vacuum where UV optics often show fast degradation. Here, we present stable performance of a cavity for 266 nm light with several Watt of intra-cavity power in high vacuum despite the presence of hydrocarbons. Comparing two sets of cavity mirrors indicates that this feat is connected to the micro-chemical environment at the topmost coating layer. Our study emphasizes the need for further developments in this direction to facilitate robust, compact, and high-performing devices employing UV radiation.

Microchemical environmental regulation of POMs@MIL-101(Cr) promote photocatalytic nitrogen to ammonia

The polyoxometalates (POMs) have been shown to be highly effective as reactive sites for photocatalytic nitrogen fixation reactions. However, the effect of POMs regulation on catalytic performance has not been reported yet. Herein, a series of composites (SiW9M3@MIL-101(Cr) (M = Fe, Co, V, Mo) and D-SiW9Mo3@MIL-101(Cr), D, Disordered) were obtained by regulating transition metal compositions and arrangement in the POMs. The ammonia production rate of SiW9Mo3@MIL-101(Cr) is much higher than that of other composites, reaching 185.67 μmol·h−1·g-1cat in N2 without sacrificial agents. The structural characterization of composites reveals that the increase of the electron cloud density of W atom in composites is the key to improve the photocatalytic performance. In this paper, the microchemical environment of POMs was regulated by transition metal doping method, thereby promoting the efficiency of photocatalytic ammonia synthesis for the composites, which provides new insights into the design of POM-based photocatalysts with high catalytic activity.

Methyl-functionalized microporous metal-organic framework for efficient SF6/N2 separation

The capture and separation of sulfur hexafluoride (SF6) from nitrogen (N2) has the potential to reduce greenhouse gas emissions and provide economic benefits to the semiconductor industry. Herein, a series of metal–organic frameworks (MOFs) with different pore environments (Ni(pba)2 (pba = 4-(4-pyridyl)benzoate), Ni(3-mpba)2 (3-mpba = 3-methyl-4-(4-pyridyl)benzoate), and Co(3-mpba)2) were designed and synthesized for SF6/N2 separation. The most promising candidate is Ni(3-mpba)2, which exhibits excellent SF6 uptake capacity (63.4 cm3 g−1 at 298 K and 100 kPa) and the highest SF6/N2 selectivity (221 at 298 K and 100 kPa). X-ray diffraction analysis and theoretical calculations indicate that introducing the methyl group into Ni(3-mpba)2 alters the microchemical environment of the pores. Ni(3-mpba)2 has a smaller pore structure and more binding sites than Ni(pba)2; its structure and binding sites enhance the affinity between sulfur hexafluoride and the adsorbent. Dynamic breakthrough experiments further verify the remarkable separation performance of Ni(3-mpba)2 under simulated actual working conditions. In combination with its excellent regeneration ability and cycling performance, this porous coordination network shows great promise for SF6/N2 separation.

The mechanism of ethanol steam reforming on Co10|α-Al2O3 (0001) surface: A DFT study

ESR (Ethanol steam reforming) seems to be a promising way to produce hydrogen which has been proposed as the most desirable energy carriers to overcome the problem of fossil fuels shortage. The ESR mechanism on the optimized Co10|α-Al2O3 (0001) surface is investigated by means of DFT calculations. The results show that oxidation state of Co cluster and micro-chemical environment play important roles in the ESR reaction. C-C bond scission is favored on the Co0 site while C-O bond scission is likely to happen on the Cox+ site, and the energy barrier is influenced by the number of hydrogen and oxygen atoms that are bonded with C/O atom. ESR reaction is initiated by the O-H bond scission of ethanol on the Cox+ site: CH3CH2OH*→ CH3CH2O*→CH3*+CH2O*→CH2O*+OH*→H2COOH*→COOH*+H2*→CO*+H2*with the dehydrogenation of H2COO* as the rate-determining step.

Hollow carbon cavities decorated with highly dispersed manganese-nitrogen moieties for efficient metal-air batteries

The designed synthesis of hollow carbon chamber catalysts is central for accelerating the oxygen reduction reaction (ORR) electrocatalysis, which is the core process of renewable metal-air batteries. Nevertheless the positive effect of hollow carbon cavities on the actual ORR electrocatalysis in alkaline and neutral medium is still underexplored. Herein, manganese-decorated zeolite imidazolate frameworks coated with polydopamine (PDA) was pyrolyzed to form the hollow and macroporous carbon cavities decorated with highly dispersed manganese-nitrogen moieties (Mn-NC). The hollow carbon cavities with spacious microchemical environment can maximize the amount of atomically active sites and provide convenient mass transfer channels, cooperatively boosting the alkaline and neutral ORR via an efficient close to four-electron pathway. As result, the hollow Mn-NC exhibited much enhanced catalytic capability than Mn-C synthesized without polydopamine coating in both alkaline and neutral electrolyte. When utilized as a cathode catalyst, the homemade zinc-air battery (ZAB) and magnesium-air battery (MAB) driven by Mn-NC displayed higher peak power density and longer stable discharge time than those driven by commercial Pt/C catalyst, along with robust rate performance, showing appreciable application potential. This work may inspire more study on rational design and synthesis of hollow catalysts with boosted ORR electrocatalysis for efficient energy conversion devices including fuel cells and other metal-air batteries and beyond.

Modulating the Chemical Microenvironment of Pt Nanoparticles within Ultrathin Nanosheets of Isoreticular MOFs for Enhanced Catalytic Activity.

The catalytic activity of metal nanoparticles (MNPs) embedded in metal-organic frameworks (MOFs) is affected by the electronic interactions between MNPs and MOFs. In this report, we fabricate a series of ultrathin nanosheets of isoreticular MOFs (NMOFs) with different metal nodes as supports and successfully encapsulate Pt NPs within these NMOFs, affording Pt@NMOF-Co, Pt@NMOF-Ni1Co1, Pt@NMOF-Ni3Co1, and Pt@NMOF-Ni nanocomposites. The microchemical environment on the surface of Pt NPs can be modulated by varying the metal nodes of NMOFs. The catalytic activity of the nanocomposites toward liquid-phase hydrogenation of 1-hexene shows obvious difference, in which Pt@NMOF-Ni possesses the highest activity followed by Pt@NMOF-Ni3Co1, Pt@NMOF-Ni1Co1, and Pt@NMOF-Co in a decreasing order of activity. Obviously, increasing gradually the amount of Ni2+ nodes in the carriers can improve the catalytic activity. The difference of catalytic activity of the nanocomposites might originate from the distinct electron interactions between Pt NPs and NMOFs, as ascertained by X-ray photoelectron spectroscopy spectrum and density functional theory calculations. This work provides a rare example that the catalytic activity of MNPs could be controlled by accurately regulating the microchemical environment using ultrathin NMOFs as supports.

Fabrication of BiOCl with adjustable oxygen vacancies and greatly elevated photocatalytic activity by using bamboo fiber surface embellishment

In this demonstration, to promote the photocatalytic activity of BiOCl, environmentally friendly bamboo fiber (BF) was added into the synthesis system of BiOCl. The size of crystals and the content of oxygen vacancies (OVs) can be effectively controlled by BF. The crystal structure, morphology, light absorbance capacity, separation efficiency of photogenerated carriers, OVs, microchemical environment, active free radicals and photocatalytic performance were carefully investigated. The observations firmly confirm that BF can effectively affect the growth of BiOCl. More interestingly, the content of OVs can be easily regulated by adjusting the amount of BF. When the mass ratio of BF/BiOCl is 0.5%, the composite has the richest OVs and the best photocatalytic activity. Compared with the reference BiOCl, the degradation efficiency of tetracycline (TC) and Rhodamine B (RhB) on 0.50% BF-BOC under visible light irradiation increases by 7.2 times and 4.1 times, respectively. Moreover, the sample holds high defluorination efficiency toward destruction of perfluorooctanoic acid (PFOA) than the reference BiOCl, which can be allocated to the greatly enhanced separation efficiency of photogenerated carriers and abundant OVs. This work provides an alternative strategy for preparation of highly activity photocatalysts for water pollution treatment.

The degradation of intracrystalline mollusc shell proteins: A proteomics study of Spondylus gaederopus

Mollusc shells represent excellent systems for the preservation and retrieval of genuine biomolecules from archaeological or palaeontological samples. As a consequence, the post-mortem breakdown of intracrystalline mollusc shell proteins has been extensively investigated, particularly with regard to its potential use as a “molecular clock” for geochronological applications. But despite seventy years of ancient protein research, the fundamental aspects of diagenesis-induced changes to protein structures and sequences remain elusive. In this study we investigate the degradation of intracrystalline proteins by performing artificial degradation experiments on the shell of the thorny oyster, Spondylus gaederopus, which is particularly important for archaeological research. We used immunochemistry and tandem mass tag (TMT) quantitative proteomics to simultaneously track patterns of structural loss and of peptide bond hydrolysis.Powdered and bleached shell samples were heated in water at four different temperatures (80, 95, 110, 140 °C) for different time durations. The structural loss of carbohydrate and protein groups was investigated by immunochemical techniques (ELLA and ELISA) and peptide bond hydrolysis was studied by tracking the changes in protein/peptide relative abundances over time using TMT quantitative proteomics. We find that heating does not induce instant organic matrix decay, but first facilitates the uncoiling of cross-linked structures, thus improving matrix detection. We calculated apparent activation energies of structural loss: Ea (carbohydrate groups) = 104.7 kJ/mol, Ea (protein epitopes) = 104.4 kJ/mol, which suggests that secondary matrix structure degradation may proceed simultaneously with protein hydrolysis. While prolonged heating at 110 °C (10 days) results in complete loss of the structural signal, surviving peptide sequences were still observed. Eight hydrolysis-prone peptide bonds were identified in the top scoring shell sequence, the uncharacterised protein LOC117318053 from Pecten maximus. Interestingly, these were not the expected “weak” bonds based on published theoretical stabilities calculated for peptides in solution. This further confirms that intracrystalline protein degradation patterns are complex and that the overall microchemical environment plays an active role in protein stability. Our TMT approach represents a major stepping stone towards developing a model for studying protein diagenesis in biomineralised systems.

Surface In Situ Doping Modification over Mn2O3 for Toluene and Propene Catalytic Oxidation: The Effect of Isolated Cuδ+ Insertion into the Mezzanine of Surface MnO2 Cladding.

Heterocation insertion and substitution in tunnels and mezzanines of MnO2 present significant influences on the microchemical environment at the surfaces and interfaces. An innovative surface in situ doping modification method via Cu2+-H+/KMnO4 treatment was applied onto the Mn2O3 surface to provide Mn2O3@MnO2 nanospheres. Cu was stabilized into resulting MnO2 cladding substituting original K+ during a mild comproportionation reaction between Mn(VII) and Mn(III). The Cu25 (Cu(II): Mn(VII)atomic = 25%) catalyst shows significant promotion of the catalytic performance compared with bare Mn2O3 and Cu0 (without Cu involving). Isolated Cuδ+ was predominantly inserted into the mezzanine of the [MnO6]δ- layers in MnO2 instead of K+, leading to slight electron transfer from Cuδ+ to outermost Mn(4-ε)+ and a decrease of interlayer spacing as well as crystallinity. Such a configuration facilitates the formation of additional oxygen vacancies, promoting the redox ability and oxygen mobility at relatively low temperatures. The mechanistic study reveals that Cuδ+ in MnO2 cladding boosts the activation of toluene (methyl) to form benzoates and propene (methyl and double bonds) to form carboxylates, enhancing the chemical adsorption of reactants. Moreover, it also inhibits the unfavored accumulation of incomplete oxidized intermediates on the surface at high temperatures.

Effect of ZrO2 types on ZrSiO4 formation

The effect of various types of ZrO2 on ZrSiO4 formation was evaluated by the calcination of three types of nanosized ZrO2 (unstabilized ZrO2, 3Y–ZrO2, and 8Y–ZrO2) and amorphous SiO2 powders. Reaction was conducted in vacuum and air atmosphere. Results indicated that under a vacuum atmosphere, the yield of ZrSiO4 during synthetic reaction markedly varied when different types of ZrO2 were used. When 3Y–ZrO2 was used, the reaction reached equilibrium after only 6 h. This occurrence was facilitated by the stabilized ZrO2 tetragonal structure. ZrSiO4 synthetic mechanism by which SiO2 diffuses into a t-ZrO2 crystal structure and then ZrSiO4 nucleates and grows along on t-ZrO2 (101) planes was confirmed. That is, t-ZrO2 acts as a host for ZrSiO4 formation. However, the investigation under air atmosphere demonstrated that ZrSiO4 could be synthesized using unstabilized ZrO2 as previously reported; meanwhile, ZrSiO4 formation was nearly suppressed in samples containing Y2O3-stabilized ZrO2. This suppression was attributable to the oxygen absorption of Y2O3-stabilized ZrO2, affecting its internal micro-chemical environment and impeding ZrSiO4 nucleation.

Towards the production of natural rubber-calcium phosphate hybrid for applications as bioactive coatings

This paper assesses the morphological, structural and bio-physicochemical stability of natural rubber (NR) Hevea brasiliensis coatings incorporated with microparticles of calcium phosphate-based (CaP) bioactive ceramics. Optical and electronic spectroscopic imaging techniques were employed to successfully evaluate the NR encapsulation capability and the stability of the coating in a biologically relevant media for bio-related application, i.e., simulated body fluid (SBF). The chemical structure of the natural polymer, the microchemical environment at the NR-CaP interface and the morphology of the CaP clusters were fully characterized. Further, the response of the hybrid coating to SBF was evaluated by incubating the samples for 30 days. The hybrid coating formed on Si surface (inert substrate) exhibited both stability and biodegradability in different levels (time dependence), thus opening horizons for applications as coatings for both biomaterials and drug delivery systems.

Fluorescent and laser properties of pyrromethene 567 (PM567) doped into multi-precursors derived gel glasses

In this work, the laser dye PM567 was incorporated into various organically modified silicate gel glasses (ORMOSILs) derived by methyltriethoxysilane (MTES) and vinyltriethoxysilane (VTES) precursors mixed in various ratios. The laser performances of PM567 doped into MTES–VTES-derived ORMOSILs including the laser slope efficiency, threshold and lifetime together with the spectroscopic properties were investigated. Blue-shifts of fluorescent peaks, extended fluorescent lifetime, improved laser efficiency and lifetime of PM567 doped into ORMOSILs derived by mixed precursors of MTES and VTES have been observed, which might related to the microstructures and micro-chemical environment of the dye in ORMOSILs.

Unveiling the Role of Oxidation Debris on the Surface Chemistry of Graphene through the Anchoring of Ag Nanoparticles

The surface microchemical environment of graphene oxide (GO) has so far been oversimplified for understanding practical purposes. The amount as well as the accurate identification of each possible oxygenated group on the GO surface are difficult to describe not only due to the complex chemical nature of the oxidation reactions but also due to several intrinsic variables related to the production and chemical processing of GO-based materials. However, to advance toward a more realistic description of the GO chemical environment, it is necessary to distinguish the oxygenated fragments with very peculiar characteristics that have so far been treated as simply graphene oxide. In this way, small oxidized graphitic fragments adsorbed on the GO surface, named oxidation debris or carboxylated carbonaceous fragments (CCFs), have been here separated from commercially available GO. Spectroscopy and microscopy results indicated that the chemical nature of these fragments is different from that of GO. By using the dec...

Suppression of the hemolytic effect of mesoporous silica nanoparticles after protein corona interaction: independence of the surface microchemical environment

Mesoporous silica nanoparticles are known to induce the hemolysis of human red blood cells (RBCs) when citotoxicity assays are performed in a phosphate buffer solution (PBS). However, in a more realistic approach, the presence of blood plasma biomolecules must be considered in any nanotoxicological evaluation of porous SiO2 nanoparticles when biomedical applications through intravenous administration are aimed. In this context, it is demonstrated in this work that porous silica nanoparticles do not induce any cytotoxic effect on RBCs when hemolysis assay is done in the presence of blood plasma, regardless the surface charge (positive or negative) of the nanoparticle. The absence of hemolysis is mainly associated with the adsorption of plasma proteins on the nanoparticle surface, which leads to the formation of a stable protein coating (called protein corona or PC) that shields the original microchemical environment of bare nanoparticles.

Aqueous alteration of kamacite in CM chondrites

Abstract– The study of aqueous alteration of kamacite in CM chondrites provides insight on the conditions, products, and relative timing of aqueous alteration. We studied unaltered, partially altered, and fully altered kamacite grains from Murray, Murchison, Cold Bokkeveld, and Nogoya using optical microscopy, electron microprobe analysis, scanning electron microscopy, and Raman spectroscopy. From textual evidence and chemical analysis, we established three separate microchemical environments. 1) In a microchemical environment with a high S activity, kamacite alters to form tochilinite, P‐bearing sulfides, eskolaite, and schreibersite. Mass balance calculations show that 81% of the Fe in kamacite is removed from the alteration region, making it available for the formation of other minerals or Fe‐rich aureoles. The release of Fe can alter the mesostasis of type‐I chondrules forming cronstedtite. 2) In a microchemical environment with a high Si activity and a low S activity, kamacite alters to form cronstedtite with small accessory sulfide inclusions. 3) A microchemical environment with limited S and Si activity results in kamacite alteration forming magnetite. The resulting magnetite retains associated Ni that can distinguish it from precipitated magnetite. In addition, the accessory phases of pentlandite and apatite can be formed if S or Ca are present. Finally, we note that small tochilinite grains in the matrix lack typical Ni, P, and Co levels, suggesting that they did not form from kamacite but possibly by sulfidization of magnetite.