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The different structural‐type zeolites (FER, MFI, FAU, BEA) are investigated as catalysts in (bio)isobutanol conversion into linear butenes. The zeolites' structure and morphology are confirmed by XRD, N2 (77 K) ad(de)sorption, SEM, EDX, XPS, and 27Al, 29Si, 1H MAS NMR, 1H‐29Si CP MAS NMR. The nature and strength of acid‐base sites are determined by FTIR spectroscopy of adsorbed pyridine, potentiometric titration, and TPD of NH3/CO2/H2O with MS control. The acid‐base properties of the zeolites′ surfaces influence their catalytic properties in the target process. The higher selectivity towards linear butene isomers achieved over FER and MFI can be explained by the high strength and density of Brønsted acid sites (over 90 % of the total surface acidity). MFI might be regarded as a potential material for the creation of novel catalysts for isobutanol conversion into linear butenes at moderate temperatures (448–473 K) since it offers greater operating stability throughout the process. [ABSTRACT FROM AUTHOR]

Here, poly(N‐acryloylglycinamide‐co‐vinyltriazole) p(NAGA‐co‐VTZ) supramolecular polymer hydrogel doped with carbonized and activated polypyrrole nanotubes as a high‐strength self‐healable material is presented for supercapacitors. Initially, the p(NAGA‐co‐VTZ) hydrogel films are synthesized by photopolymerization of N‐acryloylglycinamide and 1‐vinyl‐1,2,4‐triazole without the use of any cross‐linkers. The hydrogels demonstrated remarkable self‐healing ability via hydrogen bonding at temperatures above upper critical solubility temperature, excellent mechanical properties (0.86 MPa), large stretchability (1300%) and cut resistance. Subsequently, carbonized and ethanol/KOH‐activated polypyrrole nanotubes (acNTs) are prepared as the active material for electrochemical double‐layer capacitors (EDLC). Then, a symmetric self‐healable supercapacitor employing p(NAGA‐co‐VTZ) hydrogel, acNTs and aqueous 3 m KCl solution is assembled. Cyclic voltammetry and galvanostatic charge–discharge measurements show that the prepared device gives a specific capacitance of 282.62 F g−1 at 0.2 A g−1 and a high areal capacitance of 316.86 mF cm−2 at a scan rate of 10 mV s−1. Importantly, the supercapacitor operates over a wide voltage window (0–1.2 V) and provides excellent cyclic performance with capacitance retention of 97% after 10 000 cycles and 94% after self‐healing. In summary, the developed self‐healable supercapacitor exhibits considerable potential as a high‐performance energy storage device. [ABSTRACT FROM AUTHOR]

Nanocellulose constitutes a sustainable and biobased solution both as an efficient sorbent material for water treatment and as support for other inorganic nanomaterials with sorbent properties. Herein, we report the synthesis of a nanocomposite by deposition of in situ-generated silver nanoparticles (AgNPs) onto TEMPO-oxidized cellulose nanofibers (TOCNFs). Following an in-depth analytical investigation, we unveil for the first time the key role of AgNPs in enhancing the adsorption efficiency of TOCNF toward Cd2+ ions, chosen as model heavy metal contaminants. The obtained nanocomposite shows a value of Cd2+ sorption capacity at equilibrium from 150 mg L–1 ion aqueous solutions of ∼116 mg g–1 against the value of 78 mg g–1 measured for TOCNF alone. A combination of field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS) analyses suggests that Cd2+ ions are mainly adsorbed in the neighborhood of AgNPs. However, XPS characterization allows us to conclude that the role of AgNPs relies on increasing the exposure of carboxylic groups with respect to the original TOCNF, suggesting that these groups are still responsible for absorption. In fact, X-ray absorption spectroscopy (XAS) analysis of the Cd–K edge excludes a direct interaction between Ag0 and Cd2+, supporting the XPS results and confirming the coordination of the latter with carboxyl groups. [ABSTRACT FROM AUTHOR]

The electrocatalytic properties of advanced metal-oxide catalysts are often related to a synergistic interplay between multiple active catalyst phases. The structure and chemical nature of these active phases are typically established under reaction conditions, i.e. upon interaction of the catalyst with the electrolyte. Here, we present a fundamental surface science (scanning tunneling microscopy, X-ray photoelectron spectroscopy, and low-energy electron diffraction) and electrochemical (cyclic voltammetry) study of CeO2(111) nanoislands on Pt(111) in blank alkaline electrolyte (0.1 M KOH) in a potential window between −0.05 and 0.9 VRHE. We observe a size- and preparation-dependent behavior. Large ceria nanoislands prepared at high temperatures exhibit stable redox behavior with Ce3+/Ce4+ electrooxidation/reduction limited to the surface only. In contrast, ceria nanoislands, smaller than ∼5 nm prepared at a lower temperature, undergo conversion into a fully hydrated phase with Ce3+/Ce4+ redox transitions, which are extended to the subsurface region. While the formation of adsorbed OH species on Pt depends strongly on the ceria coverage, the formation of adsorbed Hads on Pt is independent of the ceria coverage. We assign this observation to intercalation of Hads at the Pt/ceria interface. The intercalated Hads cannot participate in the hydrogen evolution reaction, resulting in the moderation of this reaction by ceria nanoparticles on Pt. [ABSTRACT FROM AUTHOR]

A series of hydrotalcite-derived Mg–Al oxide systems with Mg/Al atomic ratios of 2 and 3 were synthesized. The hydrotalcite of Mg–Al-2 and Mg–Al-3 samples was prepared for 24 h, and Mg–Al-2-Fast and Mg–Al-3-Fast samples were kept only for 1 h. The physicochemical characteristics of the samples were studied by X-ray diffraction, scanning electron microscopy, and 27Al nuclear magnetic resonance. The surface area of the samples was determined by low-temperature N2 ad(de)sorption at 77 K. NH3 and CO2 temperature-programmed desorption was applied to determine the acid and base sites of the surface. Based on the study of Mg–Al oxide samples with different times of hydrotalcite preparation, it was found that reducing the maturation time of the mother liquor after coprecipitation from 24 to 1 h increased the volume and the surface area of mesopores and external specific area of the samples, and also the concentration of weak and medium weak base sites. These in turn increase the activity of the catalysts and the selectivity of 1-butanol formation in the process of Guerbet condensation of ethanol. The highest 1-butanol selectivity of 64% and the yield of 23.4% are achieved over the Mg–Al-2-Fast catalyst at 548 K (with stable selectivity of 64% up to 12 h). [ABSTRACT FROM AUTHOR]

In this work, we prepared a promising catalyst for propane oxidation composed of ruthenium supported on polycrystalline hollow CeO2 nanospheres. It was found that the Ru loading on the CeO2 support strongly improves its catalytic activity, decreasing the T50 by about 200 °C (from 500 to about 300 °C). By utilizing several ex situ techniques (XRD, HR-STEM, Raman spectroscopy, ICP analysis) and in situ NAP-XPS, we investigated the effect of different pre-treatments (calcination, reduction, and C3H8 oxidation reaction) on the morphology, structure, and chemical state of the Ru/CeO2 catalyst. The correlations between the chemical state of ruthenium in the Ru/CeO2 catalyst and its activity in C3H8 oxidation received particular attention. Here, it is shown for the first time that the Ru/CeO2 interaction with an oxygen-rich atmosphere (C3H8 + O2 (1 : 10)) at ≥300 °C results in ruthenium oxidation to volatile RuO4, leading to Ru evaporation/desorption from the outer surface and homogeneous high dispersion inside the powder catalyst. [ABSTRACT FROM AUTHOR]

Here, the concept of preferential leaching of cerium oxide on ternary Pt–C–CeO2 compound is demonstrated in order to develop a cost‐effective catalyst for the cathode in proton exchange membrane fuel cells. The Pt–C–CeO2 thin film catalyst is prepared by simultaneous magnetron co‐sputtering of Pt, C, and CeO2. The morphology, structure, and composition of the Pt–C–CeO2 layer are characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction. Both half‐cell and single‐cell tests are performed to determine its activity and durability. During an activation electrochemical cycling procedure, CeO2 is leached from the compound, leaving behind a porous Pt–C matrix which exhibits almost 3 times higher electrochemically active surface area in comparison with pure Pt with identical loading before and even after accelerated degradation tests in the half‐cell. When used as the cathode in a single‐cell membrane electrode assembly, decomposed Pt–C–CeO2 also shows greater power density than pure Pt. [ABSTRACT FROM AUTHOR]

AgCu Janus nanoparticles (NPs) were prepared by coating of Ag NPs in flight. The Ag NPs, produced by a gas aggregation source, were coated with Cu during their flight through a tubular magnetron (TMG). Their structure and chemical composition were studied to establish their dependence on the TMG's operational parameters. The main focus was the influence of the TMG's current and magnetic field. It was found that trapping of the NPs occurred at a certain combination of these two parameters. When trapping happened, the size of the NPs and their Cu content increased significantly. We have demonstrated that we can vary the composition of the NP's produced from pristine Ag from perfect Janus NPs with a Ag/Cu ratio of 50/50, to almost-pure Cu NPs with tiny Ag inclusions. [ABSTRACT FROM AUTHOR]

Carboxyl‐enriched nanoparticles are produced by the plasma polymerization of acrylic acid (ppAA NPs), whereas plasma‐assisted vapor‐phase deposition is used to prepare thin films of poly(ethylene oxide) (ppPEO). Sequential depositions generate phase‐separated coatings. The ppAA NPs are found to be in a glassy state, whereas thin films of ppPEO are found to be in a rubbery state. When immersed into a solution of lysozymes, the ppPEO absorbs water, which results in the dissociation of the carboxyls on the ppAA NP surface. Negatively charged carboxyls attract positively charged lysozymes. The ppPEO surface in between the NPs resists the accumulation of the protein, leading to the spatially localized adsorption of lysozymes only on the spots where the ppAA NPs are located. [ABSTRACT FROM AUTHOR]

A platinum catalyst undergoes complex deterioration process during its operation as a cathode in a proton exchange membrane fuel cell. By using in situ electrochemical atomic force microscopy (EC-AFM) with super-sharp probes, we quantitatively describe the roughening of platinum thin films during electrochemical cycling to different upper potentials, which simulate critical operation regimes of the proton exchange membrane fuel cell. The comprehensive quantitative analysis of morphology changes obtained using common roughness descriptors such as the root mean square roughness, the correlation length and the roughness exponent is correlated with cyclic voltammetry performed simultaneously. [ABSTRACT FROM AUTHOR]