The electrochemical quartz crystal microbalance (EQCM) technique was used to analyze the dissolution behavior of the Nafion®-coated platinum electrode completely or partially immersed in an acidic media. A bare smooth Pt/QC electrode and the one coated with a 0.77 μm Nafion® thin film were used as the working electrodes. The frequency changes in the Nafion®-coated Pt/QC electrodes, which were partially immersed in 0.5 M H2SO4 at 298K, were similar to those of the completely immersed Pt/QC electrodes during potential sweeps. These results indicated that the frequency change in the Nafion®-coated Pt/QC electrode was successfully applied to modeling and analyzing Pt dissolution at the actual PEFC cathode, and we called the new analytical method the “super-meniscus EQCM technique”.
We have developed a hybrid device (HLIC: Hybrid Lithium-Ion Capacitor) which combined a lithium ion capacitor (LIC) element and a lithium ion battery (LIB) element in the electrode components. The HLIC has a common negative electrode and two positive ones. The common negative electrode is including a negative electrode collector foil having through-holes. The two positive electrodes are; the first positive electrode (AC) containing particles of activated carbon and the second positive electrode (LFP) containing particles of a lithium-containing metal compound (LiFePO4) as an active material. The HLIC has a life-extending effect to the cycle life of a LIB. A HLIC cell which has a common negative electrode and two set of AC and LFP positive electrodes were studied using eight reference electrodes embedded around the common negative electrode. The electric current through the AC1 and LFP1 was measured separately by using two ammeters. The AC2 and LFP2 were not connected. Sharing of total current to the AC1 and LFP1 positive electrodes was occurred during charge-discharge tests. The sharing of current can be one of the life-extending effects of the HLIC. The potentials in the horizontal plane of the AC2 and LFP2 side were uniform during the charge-discharge tests, but a little change was observed at the area close to the AC1 and LFP1.
Aluminum foil is ultrasonically and electrochemically etched in a mixed aqueous solution of hydrochloric and sulfuric acid while varying etching time and ultrasound frequency. Next, aluminum oxide is formed by anodizing in a boric acid solution. Higher capacitance (92.4 μF cm−2) is obtained at the best etching time of 240 s and better ultrasound frequency of 120 kHz. Furthermore, higher ultrasound frequency leads to higher specifi c capacitance and longer etching time also leads to higher specific capacitance except an etching time of 300 s.
The effectiveness of a coulomb controller in improving the uniformity of multilayer structures was investigated by electrodepositing Co-Cu/Cu multilayers by a potentiostatic single bath method with a target layer thickness of 5 nm. Current analysis and cross-sectional field-emission scanning electron microscopy observations revealed that the layer thickness fluctuated when it was controlled by the deposition time. However, the thickness variation obeyed Faraday's law. Another sample was electrodeposited using a coulomb controller, which controls the layer thickness by the quantity of electricity. The layer thickness was constant in this sample.