Activity In Acid Solution Research Articles

N-Co-O Triply Doped Highly Crystalline Porous Carbon: An Acid-Proof Nonprecious Metal Oxygen Evolution Catalyst.

In comparison with nonaqueous Li-air batteries, aqueous Li-air batteries are kinetically more facile and there is more variety of non-noble metal catalysts available for oxygen electrocatalysis, especially in alkaline solution. The alkaline battery environment is however vulnerable to electrolyte carbonation by atmospheric CO2 resulting in capacity loss over time. The acid aqueous solution is immune to carbonation but is limited by the lack of effective non-noble metal catalysts for the oxygen evolution reaction (OER). This is contrary to the oxygen reduction reaction (ORR) in acid solution where a few good candidates exist. We report here the development of a N-Co-O triply doped carbon catalyst with substantial OER activity in acid solution by the thermal codecomposition of polyaniline, cobalt salt and cyanamide in nitrogen. Cyanamide and the type of cobalt precursor salt were found to determine the structure, crystallinity, surface area, extent of Co doping and consequently the OER activity of the final carbon catalyst in acid solution. We have also put forward some hypotheses about the active sites that may be useful for guiding further work.

Facile synthesis of cobalt and nitrogen co-doped graphene networks from polyaniline for oxygen reduction reaction in acidic solutions

Co and N co-doped graphene networks derived from polyaniline nanofibers can show high oxygen reduction activity in acidic solutions.

Metal–organic framework-based CoP/reduced graphene oxide: high-performance bifunctional electrocatalyst for overall water splitting

Efficient and cost-effective electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), especially bifunctional catalysts for overall water splitting, are highly desired. In this work, with rationally designed sandwich-type metal-organic framework/graphene oxide as a template and precursor, a layered CoP/reduced graphene oxide (rGO) composite has been successfully prepared via pyrolysis and a subsequent phosphating process. The resultant CoP/rGO-400 exhibits excellent HER activity in acid solution. More importantly, the catalyst manifests excellent catalytic performances for both the HER and OER in basic solution. Therefore, it can be utilized as a bifunctional catalyst on both the anode and cathode for overall water splitting in basic media, even displaying superior activity to that of the integrated Pt/C and IrO2 catalyst couple.

Ditungsten carbide nanoparticles encapsulated by ultrathin graphitic layers with excellent hydrogen-evolution electrocatalytic properties

Ultrathin graphitic layer-encapsulated ditungsten carbide nanoparticles with sizes smaller than 10 nm were synthesized by a one-step protocol, exhibiting a superior HER activity in acidic solution.

Effect of Ionic Liquids on Synthesis of Ag/TiO2 Catalyst in Water Electrolysis.

Effective Ag/TiO2 catalyst was synthesized using ionic liquids in water electrolysis. Silver was impregnated on TiO2 particles with various ionic liquids to examine the electrocatalytic activity in acid solution. Among the ionic liquids, [Bmim][CF3SO3] was most effective to prepare Ag/TiO2 particle in cyclic voltammograms. The current density over the sample was higher than 0.02 A/cm2. Furthermore, the catalyst synthesized using TiO2 particle prepared using binary ionic liquid (Ag/TiO2-IL) showed better electocatalytic activity, 0.023 A/cm2, under identical conditions.

Mo2C Nanoparticles Decorated Graphitic Carbon Sheets: Biopolymer-Derived Solid-State Synthesis and Application as an Efficient Electrocatalyst for Hydrogen Generation

The present work reports on the preparation of Mo2C nanoparticles decorated graphitic carbon sheets (Mo2C/GCSs) via a biopolymer-derived solid-state reaction between (NH4)6Mo7O24·4H2O and sodium alginate at 900 °C under Ar. As a novel hydrogen evolution reaction electrocatalytst, the Mo2C/GCSs hybrids exhibit high activity in acidic solutions with an onset potential of 120 mV, a Tafel slope of 62.6 mV dec–1, and an exchange current density of 12.5 × 10–3 mA cm–2. Moreover, such Mo2C/GCSs catalysts also show excellent durability during long-term 3000 cycles.

Fabrication phosphomolybdic acid–reduced graphene oxide nanocomposite by UV photo-reduction and its electrochemical properties

Phosphomolybdic acid-reduced graphene oxide (PMoA-rGO) nanocomposites are fabricated by a photochemical reduction method. They are characterized by ultraviolet-visible spectra, scanning electron microscope images, Fourier transform infrared spectroscopy, Raman spectra and X-ray photoelectron spectroscopy in order to confirm that oxygen-containing functional groups on GO are replaced by PMoA and that GO is reduced to rGO in the photo-reduction process. The electrochemical properties of PMoA-rGO are investigated by cyclic voltammetry, which shows that the PMoA-rGO modified glassy carbon electrode has high electrocatalytic activity in acid solution via a fast, surface-controlled electron transfer process. The results indicate that the use of rGO not only increases the electroactive surface area, but also facilitates electron transfer due to its high electric conductivity.

Morphology Effect on Electrocatalytic Activity of TiO2Spheres Synthesized by Binary Ionic Liquids in Water Electrolysis

Titania spheres were synthesized using binary ionic liquids to examine the electrocatalytic activity in acid solution. The morphology of particles was significantly different with the composition of ionic liquids. Among the binary ionic liquids, four set of mixtures led to the formation of sphere with various sizes. The morphology and structure of particles were characterized by XRD, physisoption and SEM analysis. All samples possessed an anatase phase after calcinations at . The structural properties of the samples were varied significantly with the morphology. In cyclic voltammograms, the morphology of spheres affected the electrocatalytic activity in water electrolysis. Among the samples, [Omim][]+[Hmim][] was the most effective ionic liquid to synthesize sphere with optimum morphology showing the highest electocatalytic performance.

Degradable, pH-sensitive, membrane-destabilizing, comb-like polymers for intracellular delivery of nucleic acids

This report describes the design and synthesis of a new series of degradable, pH-sensitive, membrane-destabilizing, comb-like polymers that can enhance the intracellular delivery of therapeutic nucleic acids. These comb-like polymers are based on a diblock polymer backbone where the first block is a copolymer of pH-sensitive ethyl acrylic acid (EAA) monomers and hydrophobic butyl methacrylate (BMA) or hexyl methacrylate monomers. The second block is a homopolymer of N-acryloxy succinimide (NASI) or ß-benzyl l-aspartate N-carboxy-anhydride (BLA-NCA) monomers, which are functionalized to allow controlled grafting of hydrophobic HMA and cationic trimethyl aminoethyl methacrylate (TMAEMA) copolymers via acid-labile hydrazone linkages. These comb-like polymers displayed high hemolytic activity in acidic solutions, which increased with the increase in polymer concentration. All comb-like polymers degraded into small fragments upon incubation in an acidic solution (pH 5.8) due to hydrolysis of the hydrazone linkages connecting the hydrophobic/cationic grafts to the polymer backbone. Comb-like polymers successfully complexed anti-GAPDH siRNA molecules into serum- and nuclease-stable particles, which successfully silenced GAPDH expression at both the mRNA and protein levels. These results collectively indicate the potential of these new comb-like polymers to serve as vehicles for effective intracellular delivery of therapeutic nucleic acids.

Enhancing electrochemical and electrocatalytic activities of polyaniline via co-doping with poly(styrene sulfonate) and gold

Polyaniline (PANI), polyaniline doped with poly(styrene sulfonate) (PANI–PSS), polyaniline doped with gold (PANI–Au) as well as polyaniline co-doped with poly(styrene sulfonate) and gold (PANI–Au–PSS) have been prepared using the interfacial polymerization method under similar conditions. The morphology and chemical structure of the products were examined by scanning electron microscopy, UV–vis adsorption spectroscopy and Fourier transform infrared spectroscopy. Electrochemical techniques were used to study their electrochemical and electrocatalytic activities. The results demonstrate that PANI has the highest electrochemical activity in acidic solutions among the investigated species, while with the pH values increasing from pH 6.98 to 9.18, PANI–PSS and PANI–Au–PSS exhibit much better electrochemical activity than PANI and PANI–Au, indicating that PSS plays a vital role in improving the electroactivity of PANI in neutral and basic solutions. The doping of Au alone with PANI is not the same effective as the PSS in the enhancement of electrochemical and electrocatalytic activities, whereas the co-use of Au and PSS has a synergistic contribution on the improvement of electrocatalytic activity of PANI, and therefore the ternary PANI–Au–PSS composite exhibits the strongest electrocatalytic ability to the oxidation of ascorbic acid and the reduction of hydrogen peroxide in neutral solutions.

Effect of Preparation Conditions of Sol–Gel-Derived Co–N–C-Based Catalysts on ORR Activity in Acidic Solutions

Using a Co oxide ethanol-based sol as a precursor solution, nitrogen (N)- and carbon (C)-containing ligands [1,2 phenylene diamine (phen) and ethylene diamine (en)] were added to produce an oxygen reduction reaction (ORR) catalyst precursor. After adsorption on carbon powder, heat-treatment in an inert atmosphere at , and the addition of Nafion as a binder, the powdered mixture was coated on a glassy carbon electrode and evaluated for its ORR activity in 0.5 M . The catalyst–carbon powder ratio, heat-treatment temperature, ligand type, and ligand:Co ratio were optimized, and the effect of increased catalyst layer thickness, particle size, and C support was also determined. It was concluded that a phen-based catalyst with a metal to ligand ratio of 1:2, a heat-treatment at , and a concentration of 4 wt % Co was the most active, selective, and stable ORR catalyst material of the materials developed in the present work. X-ray photoelectron spectroscopy and X-ray diffraction analysis showed the formation of both Co metal and units upon heat-treatment, with the most active catalyst having a 5.3:1 overall N–Co ratio.

Electrosynthesis of poly(o-phenylenediamine) in ionic liquid and its properties

Ionic liquid 1-ethyl-3-methylimidazolium bromide ([EMIM]Br) and N-methylimidazolium tetrafluoroborate ([HMIM]BF4) have been used as solvent and electrolyte for the electropolymerization of o-phenylenediamine at glassy carbon electrode by cyclic voltammetry. It was found that monomer was more easily oxidized in ionic liquid than acidic aqueous solution, and oxidative potential was reduced by 0.725 and 0.455 V, respectively. Electrode modified with poly(o-phenylenediamine) (PPD) has obvious electrochemical activity in acid solution (pH 1–4). The apparent diffusion coefficient (D app) of PPD film is measured by chronocoulometry and chronoamperometry. The polymer structure is measured by UV and IR. IR spectrometry reveals that poly(o-phenylenediamine) has phenazine ring structure. The heat stability of polymer is observed from thermogravimetry.

Controlling solubility of polymeric anions in supramolecular assemblies with poly(aniline) for microsensors and actuators in human tissue

The supramolecular assembly of poly(aniline) and poly(vinylsulfonate) (PAni/PVS) represents a particularly suitable catalytic material for oxidation of Vitamin C in sensor applications. PAni/PVS assemblies were prepared on platinum at increasing deoxygenation levels (LD → MD → HD) and in two thickness sizes of 2 μm (thick) and 200 nm (thin). Thick HD disks with diameters of 500 μm and 2 μm were stable over 90 min in a stirred buffer solution at pH 7 containing 300 μM Vitamin C. Stirring stability was lost after storage in air, but not after storage under argon. In MD disks PVS was partly lost after 3 h exposure to unstirred neutral buffer solution. Loss could be significantly reduced by oxidative enforcement with ferulic acid (F), a precursor of plant lignin. Application of elliptical F-PAni/PVS microelectrodes with diameters of 20 μm × 30 μm in brain parenchyma of rats showed surprisingly weak influence of intraperitoneal Vitamin C injections on the brain tissue level of Vitamin C. After 3 h of tissue exposure poly(aniline) redox activity in acidic solution decreased slightly. Factors which caused enhanced PVS solubility are discussed in detail.

Preparation of conductive polyaniline/chlorosulfonated polyethylene composites viain situ emulsion polymerization and study of their properties

The conductive composites of polyaniline (PAn) and chlorosulfonated polyethylene (CSPE) were prepared by polymerization of aniline in the presence of CSPE, using a direct, one-step in situ emulsion polymerization method. The polymerization of aniline was performed in an emulsion comprising water and xylene containing CSPE in the presence of dodecylbenzene sulfonic acid, which acts both as a surfactant and a dopant for PAn. The composites can be processed by either melt method (MP) or solution method (SP). Conductivity of the composites obtained by different processing methods shows different percolation thresholds: 14 wt % for MP samples and 22 wt % for SP samples. At the same content of PAn, the conductivity of MP composites is higher than that of SP composites. The relationships between mechanical properties and PAn content obtained by the two different processing methods were also investigated. When PAn content of MP samples is between 12 and 18 wt %, the composites behave like a thermoplastic elastomer with tensile strength at 6–8 MPa, ultimate elongation > 400% and permanent set < 30%. The conductivity of composites obtained by SP method after secondary doping with m-cresol is about 6 orders of magnitude higher than the original at below 18 wt % PAn content and the percolation threshold for conductivity is lowered to 3 wt % PAn content. The composite shows no electrochromic activity in acidic solution of LiClO4 in propylene carbonate, but after secondary doping exhibits electrochromic activity even in neutral electrolyte. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 845–850, 2000

Isolation and Characterization of a Novel Ice-nucleating Bacterium,Pseudomonassp. KUIN-4, Which Has Stable Activity in Acidic Solution

A novel ice-nucleating bacterium, KUIN-4 was isolated from a cherry leaf, which was unsusceptible to frost injury. Strain KUIN-4 was identified as Pseudomonas sp. from its characteristics and taxonomies; the optimum temperature and pH for its growth were 18°C and 4.5, respectively. When strain KUIN-4 was cultured aerobically in CYE medium (pH 4.5) for 48 h at 18°C, the ice-nucleating activities of strain KUIN-4 cells and culture broth (extracellular ice-nucleating matter) after removal of the cell were obtained. The ice-nucleating temperature, T50 (°C), was indicated to be –2.8°C in cell suspensions (4.25 x 107 cell/ml) of strain KUIN-4. Also, it had become apparent that the ice-nucleating activity involved class A, B, and C structures as judged by its freezing difference spectrum in D2O versus H2O. The ice-nucleating activity of this strain as well as other ice-nucleating bacteria was significantly decreased by heat treatment (40°C, 30 min). The ice-nucleating activity from this strain had unique features, which was stable under acidic conditions (pH 3.5–5.0) and was weakly inhibited by denaturants and protein-modifying reagents.

The polarographic behaviour of rhodium(III) chlorocomplexes

It has been experimentally proved, by coulombometric measurements, that Rhodium(III) chlorocomplexes are reduced to metal at dropping mercury electrode, and we have given evidence of the reversibility of reduction process. Further, it has been studied the variation of the half wave potential as a function of chloroions activity in acid solution. The formation constants of complexed ions: RhCl +2 RhCl 2 + RhCl 3 RhCl 4 − RhCl 5 −2 RhCl 6 −3 have been compùted and the following values derived: K 1 = 2.8 · 10 2, K 1 = 3.5 · 10 4, K 3 = 8.3 · 10 3 K 4 = 1.2 · 10 7, K 5 = 5.6 · 10 4, K 3 = 2.7 · 10 8