Controlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli‐responsive ...colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus‐like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self‐assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus‐like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions.
Polyampholyte Janus‐like microgels are synthesized using the controlled, electrostatically driven self‐assembly and coacervation of growing, oppositely charged microgel precursors during precipitation polymerization. This enables the design of new drug carriers, switchable emulsion stabilizers, and adaptive catalyst carriers.
Complex coacervation enables important wet adhesion processes in natural and artificial systems. However, existed synthetic coacervate adhesives show limited wet adhesion properties, ...non‐thermoresponsiveness, and inferior biodegradability, greatly hampering their translations. Herein, by harnessing supramolecular assembly and rational protein design, we present a temperature‐sensitive wet bioadhesive fabricated through recombinant protein and surfactant. Mechanical performance of the bioglue system is actively tunable with thermal triggers. In cold condition, adhesion strength of the bioadhesive was only about 50 kPa. By increasing temperature, the strength presented up to 600 kPa, which is remarkably stronger than other biological counterparts. This is probably due to the thermally triggered phase transition of the engineered protein and the formation of coacervate, thus leading to the enhanced wet adhesion bonding.
A thermal‐responsive protein‐based robust bioadhesive was assembled through complex coacervation. The aggregation trend of valine‐rich domains and the change in the backbone conformational states reversibly triggered the phase transition and the enhanced wet adhesion bonding.
•Rh/Ce0.75Zr0.25O2/Al2O3/FeCrAl wire mesh composite catalyst after 250 h on stream.•Autothermal reforming (ATR) of diesel, gasoline, iso-octane and n-hexadecane.•Catalyst coking by fibrous carbon ...growth under diesel ATR conditions.•Coking was attributed to contamination by iron.•No morphology and microstructure degradation of catalytic coating was identified.
Front and end zones of Rh/Ce0.75Zr0.25O2−δ-ƞ-Al2O3/FeCrAl wire mesh catalytic module were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques after more than 250 h on stream under hydrocarbon fuels steam (SR) and autothermal reforming (ATR) conditions. Catalyst coking by fibrous carbon growth under diesel ATR conditions was confirmed. This process was mainly located on the surface of the catalytic coating and did not induce exfoliation and damage of coating. Coking was attributed to contamination by iron, which was confirmed by TEM and energy-dispersive X-ray spectroscopy (EDX). Despite catalyst carbonization, the composite catalyst was shown to be stable and regeneratable under hydrocarbon ATR and SR conditions, no morphology and microstructure degradation was identified in both front and end zones of the monolith.
•Alumina nanofibers (ANF).•Template-assisted wet-combustion synthesis of Ni-MOx/ANF (M = Mg, Cr, Ce) catalysts.•High dispersion and uniform distribution of Ni and MOx over ANF surface.•Pre-reforming ...of propane as a model compound of liquefied petroleum gas.•Catalytic activity increased in order Ni-MgO/ANF < Ni-CeOx/ANF < Ni-CrOx/ANF.
In the scope of transition to closed carbon cycle economy hydrogen is becoming a major energy carrier and the development of novel functional materials for its production and storage is of great interest. Liquefied petroleum gas (LPG) is one of the primary options for this purpose due to high energy density and well-developed production and transportation infrastructure. We report novel alumina nanofibers supported Ni-MOx (M = Mg, Cr, Ce) catalysts for the steam reforming of LPG, prepared via template-assisted wet-combustion synthesis using glycine as a fuel additive. High dispersion and uniform distribution of nickel and MOx species over nanofibers surface were provided by this preparation technique. The catalysts exhibited sufficient activity, stability and coking resistance in propane pre-reforming at low steam to carbon ratio and temperatures of 350–425 °C. Catalytic activity in propane pre-reforming increased in order Ni-MgO/ANF < Ni-CeOx/ANF < Ni-CrOx/ANF. High activity is most likely associated with high specific Ni surface area and red-ox properties of carriers.
Bimetallic alumina and ceria supported Pt–Co catalysts were prepared via the decomposition of a Co(H₂O)₆Pt(NO₂)₄·2H₂O double complex salt. Catalysts were tested in CO preferential oxidation (PROX). ...PtCo/Al₂O₃ catalyst exhibited high activity and selectivity. It provided the CO conversion higher than 80% and selectivity above 60% in the temperature interval 90–165°C at WHSV of 260,000cm³g⁻¹h⁻¹ and O₂/CO ratio of 0.6. XRD and TEM analysis indicated the formation of a platinum-rich Pt–Co alloy nanoparticles supported over alumina surface.
For the first time the influence of CO, CO2 and H2O content on the performance of chlorinated NiCeO2 catalyst in selective or preferential CO methanation was studied systematically. It was shown that ...the rate of CO methanation over Ni(Cl)/CeO2 increases with the increasing H2 concentration, is independent of CO2 concentration and decreases with increasing CO and H2O concentrations; the rate of CO2 methanation is weakly sensitive to H2 and CO2 concentrations and decreases with increasing CO and H2O concentrations. High catalyst selectivity was attributed to Ni surface blockage by strongly adsorbed CO molecules and ceria surface blockage by Cl, which both inhibit CO2 hydrogenation.
For the first time, selective CO methanation over Ni(Cl)/CeO2 was studied for deep CO removal from formic acid derived hydrogen-rich gases characterized by high CO2 (40–50 vol%), low CO (30–1000 ppm) content and trace amounts of water. Composite Ni(Cl)/CeO2-η-Al2O3/FeCrAl wire mesh catalyst was demonstrated to be effective for this process at temperatures of 180–220°С, selectivity 30–70%, WHSV up to 200 L (STP)/(g∙h). The catalyst provides high process productivity, low pressure drop, uniform temperature distribution, and appears highly promising for the development of a compact CO cleanup reactor. Selective CO methanation was concluded to be a convenient way to CO-free hydrogen produced by formic acid decomposition.
·Selective CO methanation over Ni(Cl)/CeO2 catalyst.·CO and CO2 methanation rates decrease with rise of CO and H2O content.·Structured Ni(Cl)/CeO2/η-Al2O3/FeCrAl wire mesh catalyst.·CO level below 10 ppm at 180–220 °C, selectivity of 30–70% and 200 L g−1h−1 flow.·CO-free hydrogen, produced by formic acid decomposition.
Nanopowders of unordered solid solution Pt0.5Co0.5 and metal-oxide composite Pt-CoOx were prepared via double complex salt Pt(NH3)4Co(C2O4)2(H2O)2·2H2O decomposition in He and air streams, ...respectively. It was shown that, compared to metallic Pt nanopowder, both Pt0.5Co0.5 and Pt-CoOx exhibited high CO preferential oxidation (CO PROX) performance under mild conditions and provided complete CO conversion with 50–100% selectivity at near-ambient temperature and WHSV of 80,000cm3g−1h−1. Operando XRD study revealed that under CO PROX conditions Pt0.5Co0.5 was stable, while Pt-CoOx underwent reduction even at 50°C and consisted of Pt and Co nanoparticles. The high performance of both (alloyed and not alloyed) Pt-Co bimetallic systems exhibits the key role of Pt-Co interface, i.e. the so-called “ensemble effect”, in the synergism.
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•Nanopowder of unordered solid solution Pt0.5Co0.5 shows high CO PROX performance.•Nanopowder of metal-oxide composite Pt-CoOx shows high CO PROX performance.•Pt0.5Co0.5 is stable under CO PROX conditions.•Pt-CoOx undergoes reduction towards Pt and Co nanoparticles under CO PROX conditions.•The key role of Pt-Co interface in the synergism
We performed computer simulations to reveal a difference in internal structures of micelles formed by AB gradient copolymers and equivalent diblock copolymers in a selective solvent. In contrast to ...distinct core–shell structure of the diblock copolymer micelles (DCM), the soluble and insoluble monomer units are less segregated in the gradient copolymer micelles (GCM). Furthermore, the concentration of the soluble units in the GCM has a maximum at the core–corona interface. The maximum is a consequence of loop formation near the interface due to the broad distribution of the insoluble units along the chain and their assembly into the core of the micelle. As a result, the interfacial area per one gradient copolymer chain is larger than the area of the diblock copolymer, and the aggregation number of the GCM is smaller. Worsening of the solvent quality (increase of attraction between the insoluble groups) enlarges the aggregation number of the DCM. On the contrary, the aggregation number of the GCM practically does not change. Furthermore, the corona of the GCM becomes less swollen because more and more insoluble units join to the core and aggregate in the corona upon solvent worsening. In other words, the GCM become smaller. Such behavior is known as a “reel in” effect detected for gradient copolymer micelles at temperature elevation.
In this work, different systems of colloidally stable, ampholytic microgels (μGs) based on poly(N-vinylcaprolactam) and poly(N-isopropylacrylamide), wherein the anionic and cationic groups are ...randomly distributed, were investigated. Fourier transmission infrared spectroscopy and transmission electron microscopy confirmed the quantitative incorporation and random distribution of ionizable groups in μGs, respectively. The control of hydrodynamic radii and mechanical properties of polyampholyte μGs at different pH values was studied with dynamic light scattering and in situ atomic force microscopy. We have proposed a model of pH-dependent polyampholyte μG, which correctly describes the experimental data and explains physical reasons for the swelling and collapse of the μG at different pHs. In the case of a balanced μG (equal numbers of cationic and anionic groups), the size as a function of pH has a symmetric, V-like shape. Swelling of purely cationic μG at low pH or purely anionic μG at high pH is due to electrostatic repulsion of similarly charged groups, which appears as a result of partial escape of counterions. Also, osmotically active counterions (the counterions that are trapped within the μG) contribute to the swelling of the μG. In contrast, electrostatic interactions are responsible for the collapse of the μG at intermediate pH when the numbers of anionic and cationic groups are equal (stoichiometric ratio). The multipole attraction of the charged groups is caused by thermodynamic fluctuations, similar to the those observed in Debye–Hückel plasma. We have demonstrated that the higher the fraction of cationic and anionic groups, the more pronounced the swelling and collapse of the μG at different pHs.
Selective CO methanation in the realistic H2-rich gas mixture containing 10 vol.% H2O and 20 vol.% CO2 was investigated over 10 wt.% Ni–, Co– and Fe/CeO2 catalysts, prepared from nitrate and chloride ...precursors. BET, XRD, HRTEM, EDX and CO chemisorption techniques were used for catalyst characterization. Among the catalysts studied, the Ni/CeO2 catalyst, prepared from NiCl2 precursor, showed the best catalytic performance. This phenomenon can be associated with inhibition of CO2 hydrogenation activity by the presence of chlorine on the catalyst surface.
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•10 wt.% Ni–, Co– and Fe/CeO2 catalysts, prepared from nitrate and chloride precursors.•Fe-based and Co(Cl)/CeO2 catalysts were inactive in CO and CO2 methanation.•Ni– and Co/CeO2 catalysts were active in both CO and CO2 methanation.•Ni(Cl)/CeO2 catalyst showed the best performance in selective CO methanation.•CO2 hydrogenation activity inhibition by the presence of chlorine on ceria surface.
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