Until the mid 1980’s, there had been only few in situ methods available for structural determination of an electrode surface in solution at atomic and monolayer levels. Nowadays, many powerful in situ techniques, such as electrochemical scanning tunneling microscopy (EC-STM), infrared reflection absorption spectroscopy (IRAS), surface-enhanced Raman scattering (SERS), and surface-enhanced infrared reflection absorption spectroscopy (SEIRAS), second harmonic generation (SHG), sum frequency generation (SFG), and surface X-ray scattering (SXS) have been widely employed to characterize the electrode surfaces under potential control with atomic and/or molecular resolution. The object of this review is to highlight some of the progress on in situ methods at solid-liquid interface with atomic and molecular levels. Several selected topics are focused on, specifically adsorbed anions on metal surface, electrocatalysis of the carbon oxide oxidation and dioxygen reduction, and direct observation of single crystal electrode surfaces.
Anodic processes in the lithium perchlorate/nitromethane (LPC/NM) electrolyte system provide a wide variety of carbon-carbon bond formation. The electrolyte solution exhibits markedly accelerated properties as a Lewis acid catalyst that even enable intermolecular reactions between unactivated alkenes and anodically generated intermediates to form unique products. The properties of the electrolyte solution and application to electrochemical reactions are reviewed.
In this review, recent development in micro- and nano-technologies based on anodizing of aluminum is introduced and several applications of anodic oxide films in the fabrication of micro-devices are also described. In the application work, aluminum covered with anodic oxide films is irradiated with a pulsed Nd-YAG laser to remove the oxide film locally and then metal, acrylic acid resin, and polypyrrole are deposited at the film-removed area electrochemically. Grooves, chambers, and through-holes on aluminum are also fabricated by the laser irradiation technique. By combining anodizing with the laser irradiation techniques and electrochemical treatments, novel fabrication processes are developed for printed circuit boards, plastic injection molds, electrochemical reactors, and freestanding structures, 3D manipulators, and also micro-printing rolls.
Our recent works on the photoelectrochemistry and fabrication of the water-splitting photocatalyst for solar energy conversion were reported. The S-dope midgap states were determined by monitoring the effect of the photocurrent on the addition of several reductants. The midgap states for the S-doped anatase TiO2 has higher redox potentials than those of the Br•/Br− and possesses the additional multiple oxidation states of S cations. The laser ablation of the BiVO4 and BiZn2VO6 photocatalytic particulates in water reduced these sizes and it was found that the thin film electrode prepared by calcining the laser-ablated BiVO4 and BiZn2VO6 suspensions showed higher photocurrent efficiencies compared with the electrodes prepared without laser-ablation. The composite electrode FTO/SnO2/BiVO4 and FTO/WO3/BiVO4 were prepared by a solution method and the photocurrent efficiencies for these electrodes were found to be increased due to the mediator effect of SnO2 and WO3, which helps the electrons in the conduction band of BiVO4 to transfer to the FTO. The new photocatalytic particulates that are active for oxygen evolution under the visible light irradiation was searched and the BiCu2PO6 was found to be active with the addition of sacrifice under the visible light irradiations.
Electrochemical characteristics of an aqueous manganese nitrate [Mg(NO3)2] electrolyte system have been investigated for electric double layer capacitor (EDLC) applications. Its electrochemical activity has been examined in a concentration range from 0.1 to 1.0 mol dm−3 by using a symmetric capacitor based on activated carbon (AC) electrodes. The capacitor performances were evaluated by impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge experiments at temperature 25°C. The observed results show essentially capacitive behaviors within a tested potential region from 0 to 0.8 V vs. an Ag/AgCl reference electrode. The cell capacitance varies with the electrolyte concentration and the measured potential window. The maximum observed capacitance was 124 F g−1 (energy density: 8.5 Wh kg−1). We have confirmed good reversibility of Mg2+ adsorption/desorption and the stability of the aqueous electrolyte within the applied potential limit. The results show an ideal capacitor nature with a significant energy density value.
Corrosive conditions, for example, high fuel utilization, crossover, and local gas leakage were studied using a single cell equipped both with twelve reference electrodes (RHEs) and with sixteen thermocouples, and changes of the distributions of temperatures and potentials in the plane of a PAFC single cell were investigated. High potential of the cathode was observed at the fuel gas starved area. High temperature zone was observed at the leak gas introduced area or at high current density area. When the hydrogen utilization was close to 100%, the maximum cathode potentials exceeded 0.9 V vs. RHE, and high possibility of corrosion was suggested at the fuel outlet area. In the case of local air leak from a tube laid in a fuel gas flow channel, the maximum cathode potential exceeded 1.2 V vs. RHE at the fuel downstream of the air leak point, and high possibility of corrosion was suggested at that area.
In the semiconductor manufacturing process, aluminum wiring is formed by reactive ion etching (RIE), and followed by residue removal by ashing and immersing wafers in post-processing solution. Inorganic based composition makes the post-processing solution become more environmentally friendly. Nevertheless, the post-processing solution often causes corrosion in the liquid phase processing. In this report, we evaluated the behavior of aluminum in a strong acidic post-processing solution, i.e., the characteristics of the galvanic corrosion, and the effects of corrosion inhibitor. It was observed that the galvanic corrosion occurred on aluminum counterpart of titanium nitride used as a barrier metal. However, it was found that by adding the ammonium polyphosphate, a corrosion inhibitor, into the post-processing solution, corrosion could be suppressed.