Large Cell Voltage Research Articles

Water electrolysis enhanced by super gravity field for hydrogen production

Water electrolysis was carried out galvanostatically under a super gravity field. The relationships of cell voltage, ohmic voltage drop reduction and overpotential reduction with gravity coefficient ( G) and current densities were studied. It was found that water electrolysis was noticeably enhanced by the super gravity field. Good linear relationships between cell voltage ( U) and logarithm of G can be obtained at all current densities. Large cell voltage reduction was achieved under the super gravity field, especially under higher gravity and at higher current densities. Energy savings were about 9–17% at 0.5 A cm −2 under the super gravity field. The cell voltage reduction was ascribed to ohmic voltage drop reduction and overpotential reduction. The share of ohmic voltage drop reduction ( iΔ R G ) in cell voltage reduction (Δ U G) was higher than 70% at all current densities. At constant cell voltage, the rate of hydrogen produced under super gravity field increased noticeably compared to that under normal gravity condition.

The polarization behavior of the anode in a microbial fuel cell

Microbial fuel cell (MFC) systems are unique electrochemical devices that employ the catalytic action of bacteria to drive the oxidation of organic compounds. These systems have been suggested as renewable energy sources for small remote devices; however, questions remain about how MFCs can be efficiently optimized for this purpose. Several electrochemical techniques have been employed in this study to elucidate the limiting factors in power production by MFCs. Impedance spectra were collected for the anode and cathode at their open-circuit potential (OCP) before and after all other electrochemical tests. Cell voltage–current curves were obtained using a potential sweep technique and used to determine the maximum power available from the system. Potentiodynamic polarization in two different potential regions was used to determine the exchange current for the reaction occurring at the anode at its OCP and to explore the polarization behavior of the anode and the cathode in a wide potential range. Cyclic voltammetry was used to evaluate the redox activity of the anode. These techniques used in combination showed that the microorganism Shewanella oneidensis MR-1 is solely responsible for the observed decrease of the OCP of the anode, the increased rate of oxidation of lactate, the larger cell voltage and the increased maximum power output of the MFC.

Ionic Liquid-Incorporated Gel Polymer Electrolytes for Ultracapacitors

Electrolytes are an important component in determining the performance and cycle life of ultracapacitors. Good electrolytes should have high conductivity, large electrochemical windows, excellent thermal and chemical stability, and negligible electrolyte depletion. Ionic liquids are ideal electrolytes to satisfy these requirements. In the present work, we developed easy-to-use methods to incorporate ionic liquids into a polymer matrix to synthesize gel polymer electrolytes. The obtained solid-state ionic liquid- incorporated gel polymer electrolytes (ILGPEs) are mechanically strong, electrochemically and thermally stable, and highly conductive. We have used these electrolytes to fabricate solid-state ultracapacitors. Large cell voltage, high performance, and long cycle life have been realized for these ultracapacitors.

Sulfur Tolerance of Solid Oxide Fuel Cells

Influence of H 2 S fuel impurity on power generation characteristics of SOFCs has been analyzed by measuring cell voltage at a given current density, as a function of operational temperature, H 2 S concentration, and fuel gas composition. Reversible cell voltage drop was observed around 1000°C, but fatal irreversible degradation occurred at lower operational temperatures, at higher H 2 S concentrations, and at lower fuel H 2 /CO ratios. Sulfur tolerance of SOFCs improved by using Sc 2 O 3 -doped ZrO 2 instead of Y 2 O 3 -doped ZrO 2 as electrolyte and/or as electrolyte component in the anode cermet. It has been found that H 2 S poisoning consists of at least two stages, i.e. an initial cell voltage drop within a few minutes to a metastable cell voltage, followed by a gradual larger cell voltage drop associated with the agglomeration of Ni particles.

Coupling of Energy to Fusion Plasmas Through Distributed and Programmable Compact Energetic Neutral Beams

This paper presents a concept of coupling energy to fusion plasmas by spatially distributed and programmable compact energetic neutral beams. These energetic sources are pencil neutral beams with energy from 1 KeV up to 4 MeV. They are formed from the electron transfer between accelerated positive and negative ions in well-proven Radio Frequency Quadrupole (RFQ) structures. Symmetry in positive and negative ion plasmas favors the trapping of both species in adjacent potential wells of a travelling wave. Since this source does not require a large charge-exchange cell and high voltage sources, its compact size allows it to be positioned at multiple locations around the fusion device with various angles of injection.The motivation for this paper is to usher a new paradigm in the heating, fueling and diagnosis of fusion devices. Large fusion device of meter scale size will need energetic beams to penetrate to its center for heating, fueling and diagnostics. Kinetic instabilities might require ion injection in specific regions of phase space at particular times. Since the beam density scales favorably with decreasing size, we have utilized advances in computer and micro-fabrication and nanotechnology to design a multiple module beam injection system. This approach makes it possible to program each beam module such that beam injection is triggered by special events inside a dynamic fusion plasma.Current research devices will need inexpensive neutral beams to test their concepts at reasonably high ion energy. This proposed program is designed to demonstrate the versatility of such programmable compact beams in fusion research and ultimate reactor applications. The same principles used to produce these energetic neutral beams are equally applicable to produce neutralized beams that have potential applications in inertial fusion to prevent charge buildup at the target.1We will first describe our method of producing neutral beam sources based on the wave-acceleration process and the wave enhanced charge-transfer process. We will then describe how our beam sources can be tested in ECRH produced linear magnetized plasma equipped with ICRH and mirror confinement.The overall objective is to demonstrate the viability and versatility of these compact neutral beams for fusion. Physics issues connected with profile and instability control and the simulation of alpha particles are topics that can be investigated.

連続自焼成式酸化マグネシウム・炭素陽極を用いるマグネシウムの電解採取に関する研究 (2,000A電解)

A self-baked anode (Söderberg type), which consisted of dntimatemixture of calcined magnesite and carbonaceous binding materials (pitch, tar and creosote), was applied in a 2000 amp magnesium reduction cell containing molten magnesium chloride and sodium chloride.The cell was operated successfully for 143 days at a bath temperature of about 700°C, an average cathodic currentdensity of 1.0A/cm2and an average anodic one of 0.3A/cm2.The results were summarized as follows.1) The cathodic current efficiency was low generally, but it was raised to 71% for the last 24 days, since the operating conditionswere improved. Its maximum value per day became 90%, which was almost the same as that in I. G. Process.2) It was very difficult to collect completely magnesium particles formed at the cathode, because some of. them were finely divided and dispersed in the electrolyte. A black film, which was composed of magnesiumoxide, carbon and iron, sometimes covered the surface of magnesium and disturbed the coagulation of them. Very small magnesium particles were also found in the sludge accumulated on the cell bottom.3) The amount of magnesium oxide consumed practically, by the anode reaction under the best condition, was estimated tobe 70% of that to be consumed theoretically. This and the previous experimental results by authors show that the prebaked anode is preferable to the self-baked anode from the viewpoint of magnesium chloride formation by the reaction of magnesium oxide withchlorine.4) The large cell voltage (about 22V) was necessaryto compensate the heat loss and to keep the bath at constant temperature (about 700°C). The ohmic voltage drop was also verylarge at various contact parts of the cell circuit, therefore a device to minimize it must be considered.5) There have been remained many unclear points in our experiment, and it is possible that we may solve them in a much larger scale electrolysis.