Enhanced electrocatalytic oxidation of methanol on Pd/polypyrrole–graphene in alkaline medium

The new electrocatalyst of Pd nanoparticles supported on polypyrrole-functionalized graphene (Pd/PPy–graphene) was reported. Microstructure, morphology and crystallinity of the synthesized materials were investigated by Fourier transform infrared spectrometry (FT-IR), scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The elements of the composite were characterized using energy dispersive X-ray spectroscopy (EDS). The results showed that the polypyrrole-wrapped graphene support successfully discrete Pd nanoparticles with the crystallite size of about 6 nm. Catalyst activity for methanol electro-oxidation in fuel cells was investigated by cyclic voltammetry (CV) and chronoamperometry. The fundamental electrochemical test results indicated that the electrocatalytic activity of Pd/PPy–graphene is much better than that of commercial catalyst for methanol oxidation.     

Pharmacokinetic variations of tetramethylpyrazine phosphate after oral administration in hepatic precancerous mice and its hepatoprotective effects

Context: Pharmacokinetics of drug may be altered by abnormal physiological functions in illness, which will affect its pharmacodynamic efficacy in turn.

Objective: To assess the preventive effects of tetramethylpyrazine (TMPZ) phosphate on hepatocarcinogenesis and its pharmacokinetic differentiations in model mice.

Methods: Diethylnitrosamine (DEN) was adopted to induce hepatic precancerous model in mice through intraperitoneal injection, and prevention efficacy of TMPZ at a dose of 162?mg/kg was examined by liver histological analysis and activities of serum marker enzymes. Pharmacokinetic variations of TMPZ between control and model mice were measured for single oral administration.

Results: DEN initiation led to a remarkable increase of serum marker enzymes, and abnormality such as bile canaliculi hyperplasia and presence of tumor cells were observed in liver histopathological examination in model mice, while the control ones revealed normal architecture. Oral treatment of TMPZ resulted in a marked reduction in serum marker enzymes and improvement in liver histopathology compared with model ones. In pharmacokinetic study, values of AUC and T_max of TMPZ became significantly greater with increase of doses in both control and model mice, which elucidated the absorption was enhanced and delayed; meanwhile, its elimination was not affected markedly. When the mice were treated at same dose, the adsorption of TMPZ in model mice was greatly improved than that in control ones, while T_max and MRT had no significant difference.

Conclusion: TMPZ was partly effective to protect liver from carcinogenesis initiated by DEN, and hepatic insufficiency could change its pharmacokinetics.     

Apparent inhibition of thermal decomposition of hydrogencarbonate ion by poly(acrylic acid). The effect of molar mass and end-group functionality

The thermal decomposition of the hydrogencarbonate ion has been previously described by a bimolecular mechanism or a unimolecular mechanism. In this work the Gibbs free energy of the competing reactions for both the unimolecular and bimolecular mechanisms was calculated for typical concentrations found in thermal desalination plants. Activity coefficients were estimated using the Pitzer equations. At low temperature the bimolecular mechanism is thermodynamically favored, while above 80 °C the unimolecular mechanism is favored, consistent with observations of alkaline scale formation in thermal desalination plants. The rate coefficient of thermal decomposition of HCO₃⁻ at 97.2 °C in the absence and presence of 10 ppm of poly(acrylic acid) (PAA) with different end groups and molar mass was determined. PAA was found to retard the rate of decomposition by up to 49% and for all end groups of PAA the rate coefficient of thermal decomposition of 40 ppm HCO₃⁻ increased with increasing molar mass. The results are consistent with PAA preventing heterogeneous decomposition of HCO₃⁻ on interfaces. The rate of partitioning of PAA to these interfaces should increase with decreasing molar mass and resulting mobility of PAA, and may also be affected by self-assembly behavior.     

Platinum–rare earth electrodes for hydrogen evolution in alkaline water electrolysis

In the new “Hydrogen Economy” concept, water electrolysis is considered one of the most promising technologies for hydrogen production. Novel electrocatalytic materials for the hydrogen electrode are being actively investigated to improve the energy efficiency of current electrolysers. Platinum (Pt) alloys are known to possess good catalytic activities towards the hydrogen evolution reaction (HER). However, virtually nothing is known about the effects of rare earth (RE) elements on the electrocatalytic behaviour of Pt towards the HER. In this study, the hydrogen discharge is evaluated in three different Pt–RE intermetallic alloy electrodes, namely Pt–Ce, Pt–Sm and Pt–Ho, all having equiatomic composition. The electrodes are tested in 8 M KOH aqueous electrolytes at temperatures ranging from 25 °C to 85 °C. Measurements of the HER by linear scan voltammetry allow the determination of several kinetic parameters, namely the Tafel coefficients, charge-transfer coefficients, and exchange current densities. Activation energies of 46, 59, 39, and 60 kJ mol⁻¹ are calculated for Pt, Pt–Ce, Pt–Sm and Pt–Ho electrodes, respectively. Results show that the addition of REs improves the activity of the Pt electrocatalyst. Studies are in progress to correlate the microstructure of the studied alloys with their performance towards the HER.     

Characterization of steel corrosion in mortar by various electrochemical and physical techniques

In the study characterization of steel corrosion in concrete at the macro- and micro-level was performed. Physical (electrical-resistance probes) and electrochemical techniques (coupled multi-electrode arrays) were implemented in order to upgrade the general information that conventional electrochemical techniques can provide. Measurements were performed in mortar exposed to periodic wetting and drying. Steel corrosion damage was assessed by micro X-ray computer tomography (CT) and SEM. The results were compared and interpreted. By combined use of micro-CT and electrochemical methods, new insights into the corrosion mechanisms of steel in concrete were obtained.     

An experimental study on the placement of reference electrodes in alkaline polymer electrolyte membrane fuel cells

The ability to accurately measure separate in situ anode and cathode overpotentials and impedance responses is still a source of debate when investigating fuel cells of planar configuration containing <100 μm thickness solid electrolytes and when using the common three-electrode arrangement. The results obtained in this study indicate that the overpotentials and impedances of the anode and cathode can be successfully measured when using two spatially separated reference electrodes and when the cathode and anode of alkaline membrane electrode assemblies (for alkaline polymer electrolyte membrane fuel cells) are precisely and optimally misaligned. The frequency dependent response between the two reference electrodes is attributed to the membrane response and the “crosstalk” between anode and cathode.     

用工业氧化钼生产钼酸钠试剂的新工艺

针对传统工艺生产钼酸钠试剂存在产量小、成本高的问题，提出了用工业氧化铝直接生产钼酸钠式剂的设想，经过小度、中试试验研究，确定了新的生产工艺，并投入批量生产，各项技术经济指标显著提高，对试剂及工业级钼酸钠的生产具有现实意义。     

Preparation of anion-exchange membrane by plasma polymerization and its use in alkaline fuel cells

A 4-vinylpyridine-based anion-exchange membrane was prepared by plasma polymerization. Scanning electron microscope and Fourier transform infrared spectroscopy showed that the membrane had uniformly thin and highly cross-linked form. The membrane was ca. 10 μm thick and its effective resistance was remarkably lower than that of a commercial membrane. In addition, modification of carbon-supported platinum with the plasma-membrane enhanced hydrogen oxidation at the gas diffusion electrode due to an increase in the triple-phase boundary. Therefore, it is shown that plasma treatment is very useful for improving the performance of alkaline fuel cell using anion-exchange membrane.     

PdBi/C electrocatalysts for ethanol electro-oxidation in alkaline medium

PdBi/C electrocatalysts (Pd:Bi atomic ratios of 95:05, 90:10, 80:20 and 70:30) were prepared by borohydride reduction using Pd(NO₃)₂.2H₂O and Bi(NO₃)₃.5H₂O as metal sources and Vulcan XC72 as support. The electrocatalysts were characterized by energy-dispersive X-ray analysis, X-ray diffraction, transmission electron microscopy and cyclic voltammetry. The activity for the ethanol electro-oxidation in alkaline medium was investigated at room temperature by chronoamperometry and the results were compared with Pt/C and PtBi/C electrocatalysts. PdBi/C (95:05) electrocatalyst showed a significant increase of performance for ethanol electro-oxidation compared to Pd/C and others PdBi/C electrocatalysts. The final current value after holding the cell at −0.4 V versus Ag/AgCl electrode for 30 min in alkaline medium for PdBi/C (95:05) electrocatalyst was about eleven times higher than the current value of the Pt/C electrocatalyst and 1.5 times higher than PtBi/C (50:50).