The kinetics of lithium transport through a composite electrode made of mesocarbon-microbeads heat-treated at 800 °C investigated by current transient analysis

Lithium transport through a mesocarbon-microbeads composite electrode was investigated in a 1 M LiPF₆ solution in ethylene carbonate/diethyl carbonate (1:1 by vol%) using a galvanostatic intermittent titration technique and a potentiostatic current transient technique. From analysis of the anodic current transient it is recognized that when the potential step is small enough for the lithium extraction potential to be below the transition potential, the lithium concentration is not fixed at the electrode surface, but the change in surface concentration with time is determined by the "cell-impedance-controlled" boundary condition. In contrast, when the potential step is large enough for the lithium extraction potential to be above the transition potential, the "real potentiostatic" boundary condition is then established at the electrode surface. Moreover, a "quasi-current plateau" was observed in a certain anodic current transient. This experimental result was theoretically analysed, based upon the modified McNabb-Foster equation as a governing equation. This strongly indicates that the difference in activation energies for lithium deintercalation between the different lithium deintercalation sites existing within the electrode accounts for the different kinetics of lithium transport between the different sites. Electronic Publication     

Characterization of polymer molecular weight distributions by ratios of molecular weight averages

The molecular weight (MW) distribution of a polymer is characterized by a hierarchy of average MWs and their appropriate combinations. For example, the ratio of the weight-average to the number-average MW is the most frequently used measure of the polydispersity of a polymer. As is well known the lower bound to this ratio is unity, and it has been shown that the upper bound is (m + 1)²/4m, where m = M_max/M_min is the ratio of the highest to the lowest MW of the MW species present in a given polymer. This upper bound corresponds to an extremely bimodal MW distribution of one half weight fraction with M_min and the other half with M_max. The behavior of the upper bound for two special unimodal distributions is investigated: one is the triangular distribution, the other the quadrilateral. The results suggest that the upper bound for all possible unimodal distributions is considerably less than the corresponding general case, especially for large values of m. For example, the maximum ratios for the quadrilateral distribution and the general upper bound are 1.04 and 1.125 for m = 2; 1.43 and 3.205 for m = 10; 2.56 and 25.5 for m = 100; 3.99 and 250.5 for m = 1000, respectively.     

Some future works of research in electrochemistry

Journal of Solid State Electrochemistry - From the brief critical overview of such energy conversion processes as fuel cell (FC), electrolysis of water/hydrochloric acid and discharge/charge of...     

Pathways of diffusion mixed with subsequent reactions with examples of hydrogen extraction from hydride-forming electrode and oxygen reduction at gas diffusion electrode

This paper covers the role of the rate-determining step (RDS) in anodic hydrogen extraction from hydride-forming electrode. In general, hydrogen extraction from the electrode proceeds through the following steps: (1) hydrogen diffusion within the electrode, (2) hydrogen transfer from absorbed state to adsorbed state, (3) electrochemical oxidation of hydrogen to hydrogen ion involving charge transfer, and (4) hydrogen ion conduction through the electrolyte. In most theoretical and experimental investigations, it has been assumed that the RDS of anodic hydrogen extraction is hydrogen diffusion through the electrode. In real situation, however, the overall rate of hydrogen extraction is simultaneously determined by the rates of two or more reaction steps including hydrogen diffusion. The present work provides the overview of anodic hydrogen extraction in case that diffusion is coupled with interfacial charge transfer, interfacial hydrogen transfer, and hydrogen ion conduction through the electrolyte as well as the purely diffusion-controlled hydrogen extraction. In addition, the mixed controlled diffusion model was also exemplified with oxygen reduction at gas diffusion electrode of fuel cell system.     

Immobilization of E. coli with autodisplayed Z-domains to a surface-modified microplate for immunoassay

Escherichia coli with autodisplayed Z-domains was reported to improve the sensitivity of immunoassays by the orientation control of antibodies. In this work, a sensitive microplate-based immunoassay is presented by immobilizing E. coli cells to a surface-modified microplate. The microplate was prepared by coating parylene-H film with formyl groups, and then covalently coupling poly-L-lysine to the parylene-H film. The E. coli cells were bound to the microplate by charge interactions between the negatively charged E. coli outer membrane and the positively charged microplate surface. In this work, the preparation of the microplate coated with poly-L-lysine is presented. The immobilization efficiency of E. coli to the modified surface was estimated to be far higher than non-specific interaction by fluorescence microscope and the optical transmittance of the modified microplate was measured to be feasible for immunoassay. The microplate-based immunoassay is demonstrated to be feasible for medical diagnosis of inflammatory diseases by using C-reactive protein as a target analyte for the medical diagnosis of inflammatory diseases.     

Synthesis of Polymer Brushes Using Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) is a robust method for the preparation of well‐defined (co)polymers. This process has also enabled the preparation of a wide range of polymer brushes where (co)polymers are covalently attached to either curved or flat surfaces. In this review, the general methodology for the synthesis of polymer brushes from flat surfaces, polymers and colloids is summarized focusing on reports using ATRP. Additionally, the morphology of ultrathin films from polymer brushes is discussed using atomic force microscopy (AFM) and other techniques to confirm the formation of nanoscale structure and organization.

Formation of polymer brushes by ATRP.     

Functionalization of polymers prepared by ATRP using radical addition reactions

Low molecular weight linear poly(methyl acrylate), star and hyperbranched polymers were synthesized using atom transfer radical polymerization (ATRP) and end‐functionalized using radical addition reactions. By adding allyltri‐n‐butylstannane at the end of the polymerization of poly(methyl acrylate), the polymer was terminated by allyl groups. When at high conversions of the acrylate monomer, allyl alcohol or 1,2‐epoxy‐5‐hexene, monomers which are not polymerizable by ATRP, were added, alcohol and epoxy functionalities respectively were incorporated at the polymer chain end. Functionalization by radical addition reactions was demonstrated to be applicable to multi‐functional polymers such as hyperbranched and star polymers.     

Synthesis of nonlinear optical polymers with large photoconductive sensitivity and transparency

Novel nonlinear optical (NLO) chromophore, 2-{3-[2-(4-methylsulfonylphenyl)vinyl]carbazol-9-yl}ethanol was synthesized and subsequently reacted with methacryloyl chloride to give a photoconducting NLO monomer ( M1 ). 2-Methylacrylic acid 2-[3-(diphenylhydrazonomethyl)carbazol-9-yl]ethyl ester ( M2 ) was also synthesized as a comonomer to enhance the carrier mobility of the NLO polymer. Photoconducting NLO polymers, P1 and P2 were obtained by the copolymerization of Ml with methyl methacrylate and M2 , respectively. These polymers were well soluble in organic solvents and showed glass transition at 177 °C and 196 °C, respectively. Polymer films of P1 and P2 were optically clear, and were transparent at wavelengths longer than 420 nm. The electro-optic coefficient (r₃₃) of poled P1 films was measured to be ∼5 pm/V at 632.8 nm. The photoconductive sensitivities of P1 and P2 were 6.2 × 10⁻¹⁴ S·cm⁻¹/mW·cm⁻² and 5.6 × 10⁻¹¹ S·cm⁻¹/mW·cm⁻².