Vol 52, No 6 (2016)

The simulation plays an important role in understanding of electrochemical behavior and internal process of lithium ion batteries. The existing finite difference method (FDM) to conduct the simulation of electrochemical process is time-consuming and computationally expensive. In this paper, a novel numerical method is proposed to accelerate the solution of the electrochemical model for a lithium ion battery. It is implemented in three steps. In the first step, physical analogy of electrochemical process to an electric circuit is used to solve charge conservation equations. In the second and third step, control volume method is used to solve species conservation equations. The simulation results show that the proposed method is much faster than the FDM by 2.2 times while maintain high accuracy which is verified by simulation and experimental data as well.

New proton-conducting membranes were synthesized from sulfonated polynaphthoyleneimide (SPNI) and polytriazole (SPTA), which are of interest for use in portable methanol fuel cells. The membrane electrode assembly (MEA) based on SPNI and SPTA showed power and voltage-current characteristics comparable to those of MEA based on Nafion®-117. The direct and reverse polarization curves coincided almost completely in shape, indicating that the obtained characteristics are stable. At a voltage of 0.3 V and a temperature of 40°С, the current density and power density reached 68 mA cm^–2 and 20.5 mW cm^–2, respectively.

Electrocatalytic oxidation of hydrazine (HZ) was studied on an stable modified glassy carbon electrode (GCE) based on poly (4-aminobenzene sulfonic acid) (4-ABSA) film. The 4-ABSA-modified glassy carbon electrode was prepared by electrochemical polymerization technique in phosphate buffer solution (PBS) (pH 7.0) and its electrochemical behavior were studied by cyclic voltammetry (CV). The polymer filmmodified electrode has very high catalytic ability for electrooxidation of HZ, which appeared as a reduced overpotential in a wide operational pH range of 5–10. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.31 × 10^–7 and 4.35 × 10^–7 M for CV; 7.89 × 10^–8 and 2.63 × 10^–7 M for CA, respectively. The results of experiments showed that prepared modified electrode have good stability, sensitivity and reproducibility for at least one month if stored dry in air.

A detailed investigation of oxygen reduction reaction (ORR) catalyzed by various metal chelates has been performed by DFT study. The results indicate that the ORR activity is determined by both of the central metal ions and chelating ligands, among which the former play a key role. For the same ligand, the central metal ions Fe, Co, or Mn give higher ORR activity, while the others almost have no catalytic activity, which is due to the fact that the O₂ and oxygen containing species are either excessively adsorbed (on central Cr) or difficult to be adsorbed on the active sites (for central Zn, Cu, or Ni). Furthermore, the ORR activity for Fe chelates is slightly increased with the increase of ligand field strength, while for other metal chelates there seems to be no clear trends between ligand field strength and ORR activity. The origin of the ORR activity for the studied metal chelates is mainly attributed to the appropriate energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).

The effect of the difference between the equilibrium potentials of the target and side reactions, the solution flow rate, and specific surface area of porous electrode (PE) on the distribution of the geometrical current density along the solution flow i_g(y) at various average current densities is studied by the method of mathematical modeling. It is found that the largest range of the variation of i_g(y) (the exponential decrease along the solution flow) is typical for the conditions that provide the limiting current mode of the target reaction on the entire PE surface in the absence of simultaneous hydrogen evolution. All changes in the operation conditions, which reduce the uniformity of the distribution of the current inside PE along the X axis and hamper reaching the limiting current mode (for example, a decrease in the equilibrium potential difference, an increase in the flow rate or specific surface area of PE) lead to more uniform distribution of i_g(y).