Finite Element Analysis of Local pH Variations in Electrolysis with Porous Electrodes, Considering Water Self-Ionization.

A finite element model was developed to simulate ion fluxes and local pH changes within and around porous electrodes during the H evolution reaction (HER) in acidic electrolytes. This model is particularly characterized by its ability to simulate scenarios in which the local pH inside and near the cathode exceeds 7, even under bulk acidic conditions (e.g.

Long Period Voltage Oscillations Associated with Reaction Changes between CO Reduction and H Formation in Zero-Gap-Type CO Electrochemical Reactor.

Zero-gap-type reactors with gas diffusion electrodes (GDE) that facilitate the CO reduction reaction (CORR) are attractive due to their high current density and low applied voltage. These reactors, however, suffer from salt precipitation and anolyte flooding of the cathode, leading to a short lifetime. Here, using a zero-gap reactor with a transparent cathode end plate, we report periodic voltage oscillations under constant current operation.

Fluorinated Amide-Based Electrolytes Induce a Sustained Low-Charging Voltage Plateau under Conditions Verifying the Feasibility of Achieving 500 Wh kg Class Li-O Batteries.

Although lithium-oxygen batteries (LOBs) hold the promise of high gravimetric energy density, this potential is hindered by high charging voltages. To ensure that the charging voltage remains low, it is crucial to generate discharge products that can be easily decomposed during the successive charging process. In this study, we discovered that the use of amide-based electrolyte solvents containing a fluorinated moiety can notably establish a sustained voltage plateau at low-charging voltages at around 3.

Construction of an autocatalytic reaction cycle in neutral medium for synthesis of life-sustaining sugars.

Autocatalytic mechanisms in carbon metabolism, such as the Calvin cycle, are responsible for the biological assimilation of CO to form organic compounds with complex structures, including sugars. Compounds that form C-C bonds with CO are regenerated in these autocatalytic reaction cycles, and the products are concurrently released. The formose reaction in basic aqueous solution has attracted attention as a nonbiological reaction involving an autocatalytic reaction cycle that non-enzymatically synthesizes sugars from the C1 compound formaldehyde.

Self-organization in an Open Reaction Network for Developing High-function Organized Molecular Systems.

Self-organized molecular systems such as liposomes and supramolecules have attracted considerable attention due to their characteristic properties. An open reaction network (ORN) is another interesting candidate for such systems; however, no stabilization mechanism has been clarified. This work reveals, by computer simulation and experiments, that a network of irreversible processes such as an ORN can be stabilized by self-organization through a full balance between all the involved irreversible processes, thus forming a steady state.

Positive Feedback Mechanism to Increase the Charging Voltage of Li-O Batteries.

The large overpotential of nonaqueous Li-O batteries when charging causes low round-trip efficiency and decomposition of the electrode materials and electrolyte. The origins of this overpotential have been enthusiastically explored to date; however, a full understanding has not yet been reached because of the complexity of multistep reaction mechanisms. Here, we applied structural and electrochemical analysis techniques to investigate the reaction step that results in the increase of the overpotential when charging.

Isotopic Depth Profiling of Discharge Products Identifies Reactive Interfaces in an Aprotic Li-O Battery with a Redox Mediator.

Prior to the practical application of rechargeable aprotic Li-O batteries, the high charging overpotentials of these devices (which inevitably cause irreversible parasitic reactions) must be addressed. The use of redox mediators (RMs) that oxidatively decompose the discharge product, LiO, is one promising solution to this problem. However, the mitigating effect of RMs is currently insufficient, and so it would be beneficial to clarify the LiO reductive growth and oxidative decomposition mechanisms.

Dynamic Changes in Charge Transfer Resistances during Cycling of Aprotic Li-O Batteries.

Various electrolyte components have been investigated with the aim of improving the cycle life of lithium-oxygen (Li-O) batteries. A tetraglyme-based electrolyte containing dual anions of Br and NO is a promising electrolyte system in which the cell voltage during charging is reduced because of the redox-mediator function of the Br/Br and NO/NO couples, while the Li-metal anode is protected by LiO formed via the reaction between Li metal and NO. To maximize the potential of this system, the fundamental factors that limit the cycle life should be clarified.

Periodic and chaotic oscillations of the electrochemical potential of p-Si in contact with an aqueous (CuSO4+HF) solution, caused by electroless Cu deposition.

Periodic and chaotic oscillations were observed for the potential of p-type Si(111) immersed in an aqueous (HF+CuSO(4)) solution, accompanied by electroless Cu deposition on p-Si. They were, to our knowledge, the first examples of open-circuit potential oscillations observed for semiconductor electrodes. The oscillations appeared only when the Cu deposit formed a continuous porous film composed of mutually connected submicrometer-sized particles.

Five current peaks in voltammograms for oxidations of formic acid, formaldehyde, and methanol on platinum.

We have found that five current peaks are present in the voltammograms in the positive and negative sweep directions for the oxidations of formic acid, formaldehyde, and methanol on Pt in the potential range of 0.05-1.8 V, although the experimental conditions for the peaks to appear are different.

Potential oscillations in galvanostatic electrooxidation of formic acid on platinum: a mathematical modeling and simulation.

We have modeled temporal potential oscillations during the electrooxidation of formic acid on platinum on the basis of the experimental results obtained by time-resolved surface-enhanced infrared absorption spectroscopy (J. Phys. Chem.

Potential oscillations in galvanostatic electrooxidation of formic acid on platinum: a time-resolved surface-enhanced infrared study.

The mechanism of temporal potential oscillations that occur during galvanostatic formic acid oxidation on a Pt electrode has been investigated by time-resolved surface-enhanced infrared absorption spectroscopy (SEIRAS). Carbon monoxide (CO) and formate were found to adsorb on the surface and change their coverages synchronously with the temporal potential oscillations. Isotopic solution exchange (from H13COOH to H12COOH) and potential step experiments revealed that the oxidation of formic acid proceeds dominantly through adsorbed formate and the decomposition of formate to CO2 is the rate-determining step of the reaction.