Search

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]