Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

https://hal.archives-ouvertes.fr/hal-02417326/document

Materials for electrochemical capacitors

https://www.chem.ccu.edu.tw/~joyce/referance/gump/IL/Chem.%20Rev.%201999,%2099,%202071.pdf

Room-Temperature Ionic Liquids. Solvents for Synthesis and Catalysis

In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

/pdf/a-review-of-electrode-materials-for-electrochemical-2cok5em0bo.pdf

A review of electrode materials for electrochemical supercapacitors

Fuel cells convert chemical energy directly into electrical energy with high efficiency and low emission of pollutants. However, before fuel-cell technology can gain a significant share of the electrical power market, important issues have to be addressed. These issues include optimal choice of fuel, and the development of alternative materials in the fuel-cell stack. Present fuel-cell prototypes often use materials selected more than 25 years ago. Commercialization aspects, including cost and durability, have revealed inadequacies in some of these materials. Here we summarize recent progress in the search and development of innovative alternative materials.

Materials for fuel-cell technologies

Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp 2 -bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.

/pdf/carbon-based-supercapacitors-produced-by-activation-of-1wqrpq3luo.pdf

Carbon-based Supercapacitors Produced by Activation of Graphene

The effect of the solution composition on the luminescence decay time following picosecond laser pulses is examined for CdS single crystals immersed in various aqueous solutions A digital simulation technique is demonstrated as an efficient tool for the quantitative analysis of luminescence decay curves in the picosecond time domain, using the exact generation function in the simulation Such analysis yields numerical values for the bulk lifetime, and for the surface recombination velocity A typical value of 25 x 10/sup -9/ s was found for the bulk lifetime of the CdS crystals employed The surface recombination velocity evaluated for an etched crystal immersed in distilled water was less than or equal to 5 x 10/sup 3/ cm/s Immersing the etched CdS crystal in a basic sulfide-polysulfide solution increased the surface recombination velocity to a level of 10/sup 6/ cm/s This indicates a photohole surface capture velocity of greater than or equal to 10/sup 6/ cm/s at a sulfide-covered CdS surface

Time-resolved photoluminescence in the picosecond time domain from cadmium sulfide crystals immersed in electrolytes

Investigation of polypyrrole/glucose oxidase electrodes by ellipsometric, microgravimetric and electrochemical measurements.

The ellipsometric characterization of Pt + Cr alloy surfaces in acid solutions

A passive fluid management component (200, 300, 620) for a direct oxidation fuel cell (600) is provided. It enables the introduction of highly concentrated methanol solutions, including neat methanol, directly into the anode (608), eliminating the need of mechanical modes of dosing and/or mixing a methanol/water solution to control the local concentration at the anode. The fluid management device of the present invention can be based on pores (204, 206, 208, 210, 212, 214) formed in the component (200) of a specific size and spacing to allow anode reactants to flow through the component towards the anode face of the membrane electrolyte of the fuel cell at a controlled rate. The pore size can be adjusted to allow the highest concentrations possible of methanol, including neat methanol, to be introduced in direct contact with the outer face of the component. The pore walls can be made to be hydrophilic to facilitate the flow of water or methanol based fluids. The component of the present invention may also include channels (302, 304, 306) formed therein which will direct the flow of carbon dioxide away from the anode of the fuel cell and to a venting or collection site.

Fluid management component for use in a fuel cell

A fuel cell system having a methanol vapor delivery component or film is pro­vided. The component includes an evaporation pad. The evaporation pad is disposed within the fuel cell generally parallel to the anode diffusion layer, but with a vapor gap provided between the evaporation pad and the anode diffusion layer. A fuel delivery conduit having at least one injection port is provided through which liquid fuel is deliv­ered from an associated source of highly concentrated fuel into the evaporation pad, at a controlled, adjustable rate. Multiple parallel liquid delivery points can also be provided. In order to ensure uniform delivery of fuel across the across the active area of the anode, one or more dispersion members are placed on the evaporation pad to effectively dis­perse the fuel laterally around each injection port.

Shimshon Gottesfeld

Papers

Time-resolved photoluminescence in the picosecond time domain from cadmium sulfide crystals immersed in electrolytes

Investigation of polypyrrole/glucose oxidase electrodes by ellipsometric, microgravimetric and electrochemical measurements.

The ellipsometric characterization of Pt + Cr alloy surfaces in acid solutions

Fluid management component for use in a fuel cell

Controlled direct liquid injection vapor feed for a DMFC