N-Terminalized Ti3 C2 Tx MXene for Supercapacitor with Extraordinary Pseudocapacitance Performance.

MXenes have demonstrated significant potential in electrochemical energy storage, particularly in supercapacitors, owing to their exceptional properties. The surface terminal groups of MXene play a pivotal role in pseudocapacitive mechanism. Considering the hindered electrolyte ion transport caused by -F terminal groups and the limited ion binding sites associated with -O terminal groups, this study proposes a novel strategy of replacing -F with -N terminal groups. The modulated MXene-N electrode, featuring a substantial number of -N terminal groups, demonstrates an exceptionally high gravimetric capacitance of 566 F g-1 (at a scan rate of 2 mV s-1 ) or 588 F g-1 (at a discharge rate of 1 A g-1 ) in 1 м H2 SO4 electrolyte, and the potential window is significantly increased. Furthermore, subsequent spectra analysis and density functional theory calculations are employed to investigate the mechanism associated with -N terminal groups. This work exemplifies the significance of terminal modulation in the context of electrochemical energy storage.

Tunable Pt-Ni Interaction Induced Construction of Disparate Atomically Dispersed Pt Sites for Acidic Hydrogen Evolution.

Developing cost-effective Pt-based electrocatalysts for the hydrogen evolution reaction (HER) is highly urgent. Herein, we report novel electrocatalysts with individually dispersed Pt active sites and tunable Pt-Ni interaction decorated on carbon-wrapped nanotube frameworks (Pt/Ni-DA). Pt/Ni-DA exhibits superior HER performance at low Pt concentrations with an ultralow overpotential of 18 mV at 10 mA cm-2 and an ultrahigh mass activity of 2.13 A mgPt-1 at an overpotential of 50 mV, which is about four times higher than that of commercial Pt/C. X-ray absorption fine structure (XAFS) confirms the extension of Pt from the Ni surface to the Ni bulk phase. Mechanistic research and density functional theory (DFT) calculations collectively reveal that the dispersibility and distribution of Pt atoms in Ni regulate the electronic configuration of Pt sites, optimizing the binding energy of reaction intermediates and facilitating electron transfer during the HER process. This work highlights the importance of the electronic structure alternation through the accommodation effect toward enhanced catalytic performance in HER.

Enhanced redox cycle of Fe3+/Fe2+ on Fe@NC by boron: Fast electron transfer and long-term stability for Fenton-like reaction.

In this work, Fe@NC/B material is successfully synthesized and in-situ supported on the surface of amorphous boron (B) using a simple pyrolysis method. The interface between Fe species and B is improved by introducing N-doped carbon (NC) layers as intermediate, fast electron transfer from B to Fe@NC can therefore be achieved, thus could promote the fast redox cycle of Fe3+/Fe2+. The obtained material can therefore activate peroxymonosulfate (PMS) effectively to degrade Bisphenol A (BPA), a fast degradation rate and a very long lifetime in a continous tubular reactor are realized. Moreover, experiments and DFT calculation indicate that Fe2+ containing species are the dominated active sites, while the exposed B atoms and structure defect of B can also activate PMS directly to produce SO4•- and 1O2 species for BPA degradation. In addition, boric acid is the oxidation product of B, which can be dissolved into the aqueous solution and expose fresh B species again for PMS activation. The combination of B with Fe@NC provide novel materials for long term PMS activation, thus could promote the real application of persulfates on an industrial scale.

Fabrication of superhydrophilic porous carbon materials through a porogen-free method: Surface and structure modification promoting the two-electron oxygen reduction activity.

HYPOTHESIS: Electrochemical manufacture of H2O2 through the two-electron oxygen reduction reaction (2e- ORR), providing prospects of the distributed production of H2O2 in remote regions, is considered a promising alternative to the energy-intensive anthraquinone oxidation process. EXPERIMENTS: In this study, one glucose-derived oxygen-enriched porous carbon material (labeled as HGC500) is developed through a porogen-free strategy integrating structural and active site modification. FINDINGS: The superhydrophilic surface and porous structure together promote the mass transfer of reactants and accessibility of active sites in the aqueous reaction, while the abundant CO species (e.g., aldehyde groups) are taken for the main active site to facilitate the 2e- ORR catalytic process. Benefiting from the above merits, the obtained HGC500 possesses superior performance with a selectivity of 92 % and mass activity of 43.6 A gcat-1 at 0.65 V (vs. RHE). Besides, the HGC500 can operate steadily for 12 h with the accumulation of H2O2 reaching up to 4090±71 ppm and a Faradic efficiency of 95 %. The H2O2 generated from the electrocatalytic process in 3 h can degrade a variety of organic pollutants (10 ppm) in 4-20 min, displaying the potential in practical applications.

Photochemistry of Nitrate Ion: Reduction by Formic Acid under UV Irradiation.

Mutual transformations of various nitrogen compounds and their reaction mechanisms have been a subject of great concern to the chemical, ecological and environmental communities. In the paper, the reactions of NO 3 - ion with small organic acids such as formic acid (HCOOH), acetic acid (CH3 COOH) and lactic acid (C3 H6 O3 ) under ultraviolet illumination were investigated systematically. It was found that NO 3 - ion is easily reduced into NO 2 - and NOx and then further into N2 and NH3 (in the form of NH 4 + ) in the process. The carboxyl anion radicals and hydrogen formed by photodecomposition of formic acid are responsible for the rapid photoreduction reaction of nitrate. The initial pH and the nitrate concentration considerably affect the product distribution and nitrate conversion. Based on a preliminary simulation study, we speculated that the photoinduced reaction may effectively proceed in oceans, lakes and rivers because of ever-increasing nitrate and organic emissions. This research is helpful to understand nitrogen cycle mechanism and develop water environmental control technologies.

Si2Ge: A New VII-Type Clathrate with Ultralow Thermal Conductivity and High Thermoelectric Property.

Based on global particle-swarm optimization algorithm and density functional theory methods, we predicted an alloyed Si2Ge compond with body centered tetragonal type VII clathrate (space group I4/mmm) built by a truncated octahedron fromed by six quadrangles and eight hexagons ([4668]). Si2Ge clathrate is 0.06 eV/atom lower than VII Si clathrate and thermally stable up to 1000 K. It has an indirect band gap of 0.23 eV, high p-doping Seebeck coefficient and n-doping electrical conductivity. It owns a low lattice thermal conductivity of 0.28 W/mK at 300 K because of its weak bonding and strong anharmonic interaction of longitudinal acoustic and low-lying optical phonons. The moderate electronic transport properties together with low lattice thermal conductivity results in a high optimal thermoeletric performance value of 2.54 (1.49) at 800 (1000) K in n (p)-doped Si2Ge.

A chemical-bond-driven edge reconstruction of Sb nanoribbons and their thermoelectric properties from first-principles calculations.

We present a theoretical study on the potential thermoelectric performance of antimony nanoribbons (SNRs). Based on density functional theory and the semiclassical transport model, the thermoelectric figure of merit ZT was calculated for various Sb nanoribbon sizes and different chiralities. The results indicated that the chemical-bond-driven edge reconstruction of nanoribbons (denoted as SNRs-recon) eliminated all of the dangling bonds and passivated all of the boundary antimony atoms with 3-fold coordination. SNRs-recon are the most energy favorable compared to the ribbons with unsaturated edge atoms. Semimetal to semiconductor transition occurred in SNRs-recon. The band gap was width-dependent in armchair SNRs (denoted as ASNRs-recon), whereas it was width-independent in zigzag SNRs (ZSNRs-recon). After nanolization and reconstruction, the TE properties of SNRs were enhanced due to higher Seebeck coefficient and lower thermal conductivity. The thermoelectric properties of n-doped ASNRs-recon and p-doped ZSNRs-recon showed width-dependent odd-even oscillation and eventually resulted in ZT values of 0.75 and 0.60, respectively. Upon increasing the ribbon width, ZT of n-doped ASNRs-recon decreased and approached a constant value of about 0.85. However, n-doped ZSNRs-recon exhibited poor TE performance compared with the others. Importantly, the ZT value could be optimized to as high as 1.91 at 300 K, which was larger than those of Sb-based bulk materials and 100 times that of thin Sb films. These optimizations make the materials promising room-temperature high-performance thermoelectric materials. Furthermore, the proposed new concept of chemical-bond-driven edge reconstruction may be useful for many other related systems.

Antitussive, expectorant and anti-inflammatory activities of different extracts from Exocarpium Citri grandis.

ETHNOPHARMACOLOGICAL RELEVANCE: Exocarpium Citri grandis (C. grandis, Huajuhong in Chinese), the epicarp of C. grandis 'Tomentosa', is used as an antitussive, expectorant and anti-inflammatory drug for hundreds of years in China. The study was aimed at evaluating the antitussive, expectorant and anti-inflammatory effects of different extracts of C. grandis, providing experimental evidence for its traditional use, and laying a foundation for its further researches. MATERIALS AND METHODS: Crude drugs of C. grandis were extracted with four kinds of solvents (water, 50% ethanol, 70% ethanol and 90% ethanol) in reflux conditions, respectively. Solutions were concentrated in reduced pressure and lyophilized in vacuum to yield the aqueous extract, 50% ethanolic extract, 70% ethanolic extract, and 90% ethanolic extract of C. grandis. Antitussive evaluations were carried out with ammonia liquor induced mice cough; expectorant effects were tested with phenol red secretion experiments in mice; anti-inflammatory effects were assessed by murine model of xylene induced ear edema in mice. RESULTS: Only aqueous and 70% ethanolic extracts of C. grandis displayed significant antitussive, expectorant and anti-inflammatory activities. Aqueous extract of C. grandis significantly decreased cough frequency caused by ammonia liquor, increased phenol red secretion and inhibited the development of ear edema in anti-inflammatory assay at the dose of 1005 mg/kg (P<0.05). However, aqueous extract of C. grandis did not lengthened the cough period. It was worth noting that, 70% ethanolic extract of C. grandis showed strong effect of decreasing cough frequency, prolonging cough period, increasing phenol red secretion and decreasing the extent of ear edema at the dose of 493 mg/kg (P<0.001). The low, middle, and high dose (247, 493, and 986 mg/kg) of 70% ethanolic extract of C. grandis showed significant antitussive, expectorant and anti-inflammatory effects in good dose dependant manner. CONCLUSION: The results supported the folk use of C. grandis (decoction of C. grandis) with scientific evidence, and indicated that the 70% ethanolic extract of C. grandis might have better effects of antitussive, expectorant and anti-inflammatory than those of aqueous extract. Further investigation needs to be conducted to study the bioactive constituents of 70% ethanolic extract of C. grandis and the mechanism of observed antitussive, expectorant and anti-inflammatory activities.

Chemical characterisation of polysaccharides from Lilium davidii.

Lilium davidii var. unicolor Salisb is known for its esculent and exceptionally sweet bulbs. This article reports the isolation and purification of a non-starch polysaccharide from the bulb tissues. The polysaccharide was fractionated by Sephadex G-100 column chromatography, giving two polysaccharide fractions. We collected the main peak polysaccharide, termed Lilium davidii polysaccharide (LDP). The molecular appearance of LDP at different concentrations was observed with atomic force microscopy (AFM) imaging, and the chemical characterisation of LDP was studied by physical, chemical and spectroscopic techniques: for example, differential scanning calorimetry (DSC) analysis, methylation analysis, GC, GC-MS, and NMR. The results demonstrate that the LDP is an amorphous powder, containing three monosaccharide molecules: D-mannose (D-Man), D-glucose (D-Glc) and D-galactose (D-Gal), with approximate molar ratios of 10 : 19 : 1. The morphology of LDP was arranged as irregular crumb-like or island forms (3-D images) when the concentration of the solution was low, and more molecules were entangled as a rugged sugar layer at high concentration. The LDP has a molecular weight of 5.17 x 10(4) g mol(-1). On the basis of methylation and GC-MS analysis, IR, NMR, the likely linkages of sugar components of LDP was described as follows: the main chain of the LDP is primarily made up of a 1,4-linked form for beta-Glc and a 1,3-linked form for alpha-Man with molar ratios of 2 : 1. On average, there is one 1,6-linked form for alpha-Gal or one 1,3-linked form for alpha-Man residues which can be substituted at 6-O from among 30 sugar residues. The reduction terminal is beta-Glc.