Katsushi Abe

The polyaniline/lithium battery

Polyaniline (PAn), synthesized by electro-polymerization, has exhibited good reversibility in an LiClO4/propylene carbonate electrolyte. The reversible specific capacity reaches 120 A h kg−1. PAn appears to be a candidate positive electrode for a secondary lithium battery because of its reversibility, high-rate discharge performance, and low self-discharge. The compatibility of the electrolyte between PAn and lithium electrodes is an important problem to be solved.

Electrochemical studies of polyaniline and its application

Abstract The weight change of polyaniline (PAn) positive electrode in LiClO 4 /propylene carbonate (PC) electrolyte during charge/discharge process was observed in situ by an electrogravimetric technique. The weight of PAn in the electrolyte increased linearly upon charge and decreased linearly upon discharge. The result suggests that the charge/discharge reaction of PAn in the non-aqueous electrolyte proceeds with doping/undoping of anion species. The anion species is supposed to be ClO4- anion solvated with 3–4 propylene carbonate molecules. The solubility of the doped anion to the solvent affects the rechargeability of PAn. Therefore, the use of HClO4 or HBF4 aqueous electrolyte is preferable for the synthesis of PAn. PAn in the non-aqueous medium is very stable even in the higher oxidized state and shows the highest discharge capacity (150 Ah/kg) of the other conducting polymers.

Study on current efficiency of steam electrolysis using a partial protonic conductor SrZr0.9Yb0.1O3−α

Abstract The current efficiency of steam electrolysis was measured in the temperature range from 460 to 600°C using a steam electrolysis cell constructed with a partial protonic conductor SrZr 0.9 Yb 0.1 O 3− α as an electrolyte and Pt cermet electrodes. The efficiency was increased with increasing partial pressure of water vapor and temperature. The results were considered in relation to the reaction rates at the anode and cathode. Under the operating conditions of steam electrolysis, the reaction rate of producing H 2 from protons at the cathode was found to be faster than that of oxidizing water vapor into protons and O 2 at the anode. Therefore, the average concentration of protons in the partial protonic conductor during electrolysis decreased. On the other hand, the average concentration of holes increased. This is considered to decrease the efficiency of steam electrolysis. It was found that the effective transport numbers of charge carriers in the partial protonic conductor were controlled by the reaction rates at the electrodes at relatively low temperatures at which the equilibria between the atmosphere and defects in the partial protonic conductor were difficult to obtain.

In Situ Electrogravimetric Analysis of Polypyrrole and Polyaniline Positive Electrodes in Nonaqueous Medium

In this paper, we have been measuring the weight change of the polymer electrodes in electrolytes during the charge/discharge process using a unique technique. The purpose of this paper is to clarify a detailed structure of the dopant in the polymer based on the results of this electrogravimetric method

Reduction of nitrogen oxide by steam electrolysis cell using a protonic conductor SrZr0.9Yb0.1O3−α and the catalyst Sr/Al2O3

Abstract A steam electrolysis cell was constructed with a high-temperature type protonic conductor, SrZr0.9Yb0.1O3−α. The reduction of nitrogen oxide (NO) by hydrogen, which was produced by a steam electrolysis cell, was examined. Helium gas with 8% O2 and 1000 ppm NO was used as a model gas for the exhaust gas from automotive engines operating under lean-burn condition. The removal efficiency of NO was measured, using steam electrolysis cells with different catalysts on the cathodes. A mixture of Pt-sponge and Sr/Al2O3 catalyst was found to be most effective for the preferred reduction of NO in the presence of excess O2. It was suggested that the preferred reduction of NO occurred via the electrochemical reduction of NO absorbed into Sr/Al2O3, not via the chemical reduction of NO by H2 gas.

Performance of electrolysis cells with proton and oxide-ion conducting electrolyte for reducing nitrogen oxide

Abstract A steam electrolysis cell was constructed with a proton conductor SrZr 0.9 Yb 0.1 O 3− α as an electrolyte. The steam electrolysis cell efficiently reduced nitrogen oxide (NO) on the cathode, using hydrogen produced by steam electrolysis as a reducing agent at around 460 °C. When a Pt/Ba/Al 2 O 3 catalyst was placed on the cathode, NO was reduced even under an O 2 -rich atmosphere. An electrolysis cell was also constructed with an oxide-ion conductor 8 Y–ZrO 2 as an electrolyte. The cell could reduce NO on the cathode, not only electrochemically electrolyzing NO directly but also chemically using hydrogen produced by steam electrolysis. However, the cell with the oxide-ion conductor could not reduce NO in an atmosphere containing O 2 .

Reduction of nitrogen oxide by a steam electrolysis cell using a proton conducting electrolyte

Abstract Removal of nitrogen oxide (NO) by electrochemical reduction was studied using a steam electrolysis cell with platinum electrodes and a proton conductor SrZr0.9Yb0.1O3 − α as the electrolyte. Without NO, the cell produced H2 with nearly 100% current efficiency in the temperature range 380–590 °C. With NO fed to the cathode, NO was effectively reduced. The main products were N2O and N2 at low current densities, and N2 and NH3 at higher current densities. When O2 was mixed into the cathode gas, NO was not reduced on the pure Pt cathode. However, ‘ Pt sponge + Sr Al 2 O 3 ’ catalyst on the Pt cathode showed a good catalytic ability for the reduction of NO supplied with O2.

Stability of SrZr0.9Yb0.1O3−α protonic conductor in atmosphere containing nitrogen oxides (NOx)

The stability of the SrZr0.9Yb0.1O3−α protonic conductor in an atmosphere containing nitrogen oxides (NOx) was investigated. When a fine powder of SrZr0.9Yb0.1O3−α with a specific surface area of about 50 m2/g was annealed at 440 °C in He gas containing 8% O2 and 0.1% NO, the formation of Sr(NO3)2 was observed by IR measurement, ion-chromatography analysis and ICP analysis. The formation mechanism of Sr(NO3)2 was examined by considering the thermodynamic equilibrium. Based on the results of the thermodynamic calculation, H2O dissolved into SrZr0.9Yb0.1O3−α was estimated to play an important role in the reaction for the formation of Sr(NO3)2 between SrZr0.9Yb0.1O3−α and NOx.