Technical Library

In order to facilitate beginners to quickly understand the meaning of some technical vocabulary, we have collected some technical terms frequently used, for example in elctrochemical and fuel cell research field.

• Electrochemical glossary
• Fuel cell glossary

TOP > Technical library > Electrochemical glossary

Laboratory Of Research & Development, BAS Inc.
Professor Noriyuki Watanabe

A-C      D-F      G-I      J-M      N-R      S-Z

A - C

	Vocabulary	Commentary
	Amperometry	A type of voltammetry. A method of measuring the flowing current with a constant potential applied to the electrodes.
	Anode	An electrode that is in a state where an electrochemical oxidation reaction occurs.
	Anode polarization	Applying a positive direction potential to the electrode, so that an oxidation reaction occurs.
	ASV	Anode stripping Voltammetry. A cathode potential is applied for a certain period of time to deposit metal ions on the electrode. After that, the electrodeposited metal is redissolved by sweeping the potential in the anode direction, the oxidation current is measured, and the metal is qualitatively and quantified. One of the extremely sensitive analysis methods.
	Auxiliary electrode	Also known as a counter electrode. Electrochemical measurements are not possible using only one working electrode. At least two electrodes are required. Together with the working electrode, they form the circuit that closes the current.
	Background current	In the current flowing through the electrode, an excess current will flow in addition to the target Faraday current. A double electric layer is formed at the interface between the electrode and the solution. That is, the capacitance (capacitor, capacitor). The charge stored in the capacitor is capacitance x voltage (charge = capacitance x voltage, Q=CxE). Changing the electrode potential means giving the potential a time change. In other words, the charge changes with time, i.e. current flows (dQ/dt=CdE/dt). This is the capacitive current or charge current. As long as the electrode potential changes with time, the capacitive current is unavoidable. This is one of the reasons for the background current.
	Bulk electrolysis	To electrolyze all the target components in the electrolytic solution into a product.
	Capacitive current	See charging current.
	Carbon nanotube	Nanoscale carbon with a single sheet of graphite closed in a tube shape. Some consist of one sheet, while others consist of several sheets concentrically formed into tubes. One of the nanotechnology that has attracted a lot of attention because of its interesting properties.
	Caromel electrode	One of the reference electrodes. It consists of mercury/mercury chloride , an also known as calomel electrode.
	Cathode	An electrode on which electrochemical reduction reactions occurs.
	Charge	Electrons have a negative charge. If the molecular species is excessive in electrons, it will be negatively charged, and if it is insufficient, it will be positively charged.
	Charging current	Also called capacitive current. A current flows in proportion to the magnitude of the time change of the potential and the double layer capacitance. Since it is not a Faraday current, it usually interferes with the measurement. This charging current always accompanies a constant potential sweep such as CV.
	Chronoamperometry	A stepwise potential is applied from the potential at which electrolysis does not occur to the potential at which electrolysis occurs, and the current after the applied potential is measured. The current decays as the reciprocal of the square root of time. When the reciprocal of the square root of time is plotted on the horizontal axis and the current is plotted on the vertical axis, parameters such as diffusion coefficient can be obtained from the slope.
	Chronoculometry	The chronograph coulombic method (CC) is part of the coulombic method. It measures the change in Coulombic charge over time and is the current integral for the chronocurrent method (CA). Therefore, it belongs to the category of pulsed voltammetry. In addition to giving the same information as CA, it also gives information about adsorption. The coulometric method includes these, but refers more to the coulometric measurements made by bulk electrolysis.
	Chronopotentiometry	A constant oxidation or reduction current is passed and the time change of the potential is measured. When the concentration of the reducing or oxidizing substance on the electrode surface becomes zero, the potential changes rapidly. The time required for this potential change is called the transition time, from which the diffusion coefficient or concentration can be obtained.
	Comparison electrode	A reference electrode.
	Concentration gradient	The spatially decreasing concentration difference is called a concentration gradient.
	Constant potential	The potential applied is in constant.
	Convection voltammetry	Ordinary voltammetry is performed when the solution is at rest. This is to avoid, as far as possible, material transport caused by the solution flow. On the other hand, convective voltammetry is an attempt to actively exploit the flow characteristics of the solution. Typical examples are the rotating electrode method and the HPLC detection method.
	Corrosion	When the dissolution of metal (anode reaction), the reduction of dissolved oxygen (cathode reaction, apparently no water, and only moisture) and the reduction of hydrogen ions (cathode reaction) occur on the metal . The electrons liberated in the anode reaction are used in the cathode reaction. This constitutes a local battery, and in this way metal anode dissolution, that is, corrosion occurs.
	Coulometry	A method of integrating the amount of current over time and measuring it as the amount of electric charge. Since the amount of charge is proportional to the number of molecules, the absolute number of molecules can be known.
	Counter electrode	Electrodes paired with the working electrode. Electrochemical measurements require at least two electrodes. The electrode that causes an electrochemical reaction to the target object is the working electrode, and the pair of electrodes is the pair of electrodes. It is absolutely necessary to allow current to flow through the working electrode. The voltage regulator precisely regulates the potential of the working electrode, but the voltage of the counter electrode will fluctuate depending on the current.
	Crystal oscillator	The piezoelectric effect of the crystal can be used to generate oscillating circuits with high frequency accuracy. It is used to measure small weight changes, such as QCM.
	CV	Abbreviation for Cyclic Voltammetry.
	Cyclic voltammetry	Cyclic Voltammetry (CV) is the most commonly used method for electrochemical studies. The method controls the electrode potentials at different scan rates, repeatedly scanned once or several times over time in a triangular waveform, the potential range is such that different reduction and oxidation reactions can occur alternately on the electrode, and a current-potential curve is recorded. Based on the shape of the curves, the degree of reversibility of the electrode reactions, the possibility of intermediates, phase boundary adsorption or new phase formation, and the nature of the coupled chemical reactions can be determined.

↑Back to top

D - F

	Vocabulary	Commentary
	Diffusion	One of the ways in which substances are transported. Driven by a concentration gradient, a molecular substance moves from a high concentration to a low concentration.
	Diffusion domination	When the electron transfer rate is high, the total reaction rate is determined by the diffusion rate. This is called diffusion dominationor diffusion rate control.
	Dissolved oxygen	Oxygen dissolved in the solution. Since it is electrochemically reduced, it often interferes with the measurement. When it gets in the way, it is temporarily removed by bubbled with an inert gas such as nitrogen.
	DPV	Derivative pulse voltammetry . When a potential pulse witha short time widthis applied, the charging current attenuates faster than the Faraday current. By setting the current sampling in the latter half of the applied pulse, the contribution of the charging current can be almost ignored. One of the pulse methods that can obtain the highest detection sensitivity along with SWV.
	E process	The electron transfer process.
	EC process	A process in which an electron transfer process and an in-solution chemical reaction process of its product occur continuously.
	ECE process	This refers to the case where the chemical reaction product in solution is accompanied by an electron transfer process by an electrochemical reaction at the electrode following the EC process.
	Electric double layer	Depending on the excess or deficient state of charge on the electrode surface, an over-arranged state of electrolyte ions (+ or - ions) is created to maintain electrical neutralization on the solution side at the interface with the solution, resulting in the formation of an electrical double layer.
	Electrochemical impedance method	A method for analyzing an electrochemical system by measuring AC impedance . In many cases, the analysis is carried out by replacing various elementary processes such as interfacial electron transfer, substance diffusion, charge charge / discharge, ion transfer, and electrical conductivity of the medium with equivalent circuits composed of electronic circuit elements and diffusion elements. An analytical method is also performed to mathematically represent phenomena, from which impedances are calculated and then compared to actual measurements.
	Electrochemical window	The potential range in which the electrodes can be polarized.
	Electrolysis	The use of electrodes to perform oxidation-reduction processes.
	Electron spin resonance spectroscopy	Electrons are subatomic particles with spin=1/2 and a negative charge. Molecular species with unpaired electrons (unpaired electrons) are called radicals and are subject to electron spin resonance (ESR). The energy levels of unpaired electrons are split in a magnetic field and the electrons are transferred between the levels by the absorption of electromagnetic waves. This is called ESR. Normally, electromagnetic waves in the microwave range are used in ESR. The obtained spectra are used to analyze the spin density distribution and structure of organic and transition metal compounds. Radicals can be generated by electrode reactions and are used in a coupled form such as EC-ESR.
	EQCM	Abbreviation for Electrochemical Quartz Crystal Microbalance. A method that combines QCM with electrochemistry. A crystal unit with a gold electrode deposited on it is used. The adsorption and precipitation on the electrodes, and the weight change and electrochemical reaction process due to their elution can be observed at the same time.
	Equivalent circuit	One of the impedance analysis methods that reconstructs a circuit by decomposing phenomena including electrochemical reactions into various elementary processes by impedance measurement and replacing them with electronic circuit elements (resistors, capacitors, inductances), Warburg elements, and other elements.
	ESR	Abbreviation for Electron Spin Resonance. Electron spin resonance.
	Faraday cage	A device that constitutes a closed space with metal containers at the same potential to prevent external noise.
	Faraday's Law	A certain amount of charge corresponds to a certain amount of molecular equivalent. 96500 coulombs are equivalent to one molecule.
	Fuel cell	The oxidation of molecular hydrogen occurs at the anode and the reduction of molecular oxygen occurs at the cathode, making it possible to extract the free energy change of the reaction that generates water from hydrogen and oxygen as electrical energy.
	Function generator	Function generator. A function for time (eg triangular, square, pulsed, stepped, etc.). Use these waveforms as the external input of the potentiostat . At present, a potentiostat integrated with this is commercially available.

↑Back to top

G - I

	Vocabulary	Commentary
	Galvanostat	A device that can output a constant current.
	Glassy carbon	Typical carbon electrode. Hard and dense. A wide potential window in the oxidation and reduction directions facilitates its use in electrochemistry. It is generally considered to have an entangled microstructure of ribbon-like graphite bands. Its surface can be interpreted as a random mixture of edge layers and substrates.
	Hemispherical diffusion	For microelectrodes , planar diffusion is predominant to spherical diffusion. Microband array electrodes such as comb-shaped electrodes exhibit semi-spherical diffusion in a semi-cylindrical shape.
	HOPG	Highly Ordered (Oriented) Abbreviation for Pyrolytic Graphite. Highly oriented pyrographite.
	Impedance	The amount obtained in relation to voltage/current. In direct current, it refers to resistance, but in alternating current, the amount obtained from this relationship is called impedance.
	Interdigitated array electrode	Two tiny forked-finger electrodes made by photolithography opposite each other. The redox reversible system allows for the oxidation (or reduction) of substances on one electrode and their reduction (or oxidation) on the other electrode (thus achieving a redox cycle, which increases detection sensitivity).
	Ion	When an electron escapes from a metal, it becomes a + ion. When an electron is deprived or added from a neutral molecule, it becomes a + ion or a - ion, respectively. Even in metals, ferrocyanate ions and permanganate ions are - ions in total. The states in which there are extra or insufficient electrons from the neutral state are called - ions and + ions, respectively.
	IPPG	IPPG (Ion Permeability Porous Glass) is a glass with many pores. It has excellent water absorption and adsorption properties and can be used in filters, translucent films, catalysts, desiccants, etc. In the field of electrochemistry, it is often used as a reference electrode liquid joint material. In the field of electrochemistry, it is often used as a reference electrode in the liquid joint material.
	iR drop	The voltage drop created by the current flowing between the working electrode and the counter electrode due to the solution resistance between the working electrode and the reference electrode (i is the current and R is the resistance, the result of the so-called Ohm's Law). Since the potentiostat cannot control this potential (thus, this resistance is also called the uncompensated solution resistance), the externally specified potential will not be accurately applied to the working electrode. The positive feedback function of the potentiostat, which is provided to compensate for this, allows for a certain degree of compensation.
	ISFET	Abbreviation for Ion Sensitive Field Effect Transistor. An ion-selective field-effect transistor. A typical pH sensor. Small solid pH meters are commercially available.
	ITO	Abbreviation for Indium-Tin Oxide. An indium oxide film formed on a glass substrate. Used as a light transparent electrode.

↑Back to top

J - M

	Vocabulary	Commentary
	Laplace equation	This is the case where the Laplacian is set to zero in the second-order partial differential equation that describes the phenomenon in the steady state. A function that satisfies this equation is called a harmonic function. Both the real part and the imaginary part of the holomorphic function are harmonic functions. In two dimensions, it is expressed as follows.
	Ligand	A compound in which a ligand is coordinated around a metal. For example, Ru(bpy)32+, a six-coordinated octahedral complex with three bipyridines, which is a bidentate ligand, coordinated around a ruthenium ion.
	Liquid-liquid interface	The interface between two immiscible liquids (such as water and dichloroethane). Electrolytes containing common ions with different concentrations can be polarized by dissolving them in two liquids, and electrodes placed in the two liquids can change the polarization potential and move the ions across the interface (Ions mobile voltanmetry).
	Luggin capillary	A prop to make a reference electrode work the same way as a reference electrode placed in the vicinity of the working electrode. The reference electrode is placed in a glass tube with a thin and curved tip. The tip of the glass tube is placed near the working electrode. The glass tip has the same potential as the working electrode, and since no current flows through the glass capillary, the reference electrode also has the same potential.
	Microelectrode	When the electrode size is about 10 microns or less, spherical diffusion occurs preferentially and the efficiency of material transport is significantly increased compared to planar diffusion. Although the absolute value of the current decreases, the current density increases by an order of magnitude. In addition, there are some excellent features, one of which is the ability to obtain a constant sigmoid-shaped CV curve.

↑Back to top

N - R

	Vocabulary	Commentary
	Nernst equation	An equation that defines the relationship between the concentration of the electrode active material and the electrode potential.
	NHE	Abbreviation for normal hydrogen electrode. Indicated platinum black electrodes under a hydrogen gas 1 atm in the strong acid concentration 1 mol/L, its potential defined as the potential base of zero (Previously used and not used in current).
	Noise	A messy signal that interferes with the desired signal.
	Non-Polarizable Electrode	An electrode where the electrode reaction is continuous and the potential cannot be changed arbitrarily. Hydrogen electrodes (platinum black/hydrogen ion/hydrogen gas), silver/silver chloride electrodes, calomel electrode, etc. are used as reference electrodes.
	Op amp	A DC amplifier with a large amplification degree in a wide frequency range, an extremely large input impedance of the two input terminals, and a small output impedance (the amplification degree is large even in direct current. The AC amplifier cannot function as an operational amplifier). Due to these features, various active circuits can be made. Normally, it is used by applying feedback from the output side to the input side, and it is used for various functions (functions, arithmetic. Operational amplifier is an abbreviation for operational amplifier and operational amplifier), inverting amplifier, voltage hollower, addition, subtraction, Integration, differentiation, various filters and more are available. Potentiostat, by potentiostat, etc., electrochemical measurements are receiving great benefit.
	Organic EL	It emits light by means of excitons generated by the recombination of electrons and holes injected into an organic material. The mechanism is similar to that of a light-emitting diode. It has been attracting attention as a thin display material.
	Oxidation	Oxidation is the reaction that captures electrons from a molecular species. Reduction, in contrast, is a reaction that gives electrons to a molecular species.
	PEEK	Abbreviation for Poly Ether Ether Ketone. polymer. A polymer material with excellent properties such as chemical resistance, heat resistance, abrasion resistance, and good moldability. It is used as a material for HPLC piping tubes and chemical instruments.
	PFC	Abbreviation for Plastic Formed Carbon. Carbon produced by highly orienting graphite powder to align the Edge plane with good electrode characteristics in one direction and exposing it to the electrode surface, and by forming a composite with glassy carbon to prevent the electrolytic solution from penetrating. Material.
	Photoelectrochemistry	Refers to the general method of combining electrochemistry and light. There are also synthesis aspects, such as the use of optical methods (such as ultraviolet-visible spectroscopy and infrared spectroscopy) to analyze electrochemical reaction products, as well as the effective use of solar energy represented by semiconductor electrodes.
	Planar diffusion	For large electrodes, diffusion is predominant in the direction perpendicular to the electrode plane.
	Polarizable electrode	An electrode that has a potential range in which current does not flow even when a potential is applied. Platinum, gold, carbon electrodes, etc.
	Polarization	A state in which current does not flow steadily even when an electric potential is applied.
	Polarography	It may mean voltammetry by broadly polarization it, but from its historical role, it is narrowly voltammetry with a mercury electrode as a working electrode.
	Potential	It is the energy state of the electrons. If the potential of the electrode is shifted toward the negative direction, the energy state of the electrons in the electrode is raised, and therefore the electrons are easily transferred to the molecules, i.e., facilitates the reduction of molecular species in solution. Conversely, if the potential of the electrode is shifted toward the positive direction, the energy state of the electrons in the electrode is lowered and the electrons in the molecule are easily transferred to the electrode, i.e., the oxidation of molecular species in solution.
	Potentiostat	A device that makes the potential of the working electrode constant with respect to the reference electrode. It is designed to accurately measure the current between the working electrode and the counter electrode and prevent current from flowing to the reference electrode.
	QCM	Abbreviation for Quartz Crystal Microbalance. A method of measuring minute weight changes using a crystal oscillator as a sensor substrate.
	Redox cycle	Redox continues to occur, resulting in a significant increase in current as a result of recycling.
	Redox reaction	Reduction is a reaction that gives an electron to a molecular species. Oxidation is a reaction that robs a molecular species of electrons. A reaction that occurs as a pair of oxidation and reduction reactions.
	Reduction	A reaction that provides electrons to a molecular species. Oxidation is the opposite, is a reaction that captures electrons from a molecule species.
	Reference electrode	An electrode used as a reference standard in electrochemical measurements. Used as a potential reference for the working electrode.
	Rotating ring disk electrode method	A disk-shaped electrode in the center, and a ring-shaped electrode concentrically on the outside, which rotate together. The solution on the surface of the electrode is flushed outward by the centrifugal force of the rotational movement of the electrode. To make up for it, the solution flows toward the electrodes with the axis of rotation as the central axis. The thickness of the diffusion layer on the electrode surface formed by such forced and steady mass transport depends on the rotation speed, and becomes thinner as the rotation speed increases. Reaction products at the disc electrode are detected at the outer ring electrode.

↑Back to top

S - Z

	Vocabulary	Commentary
	Salt bridge	A tool used to provide electrical conduction between two solutions that you do not want to mix. An example is the agar bridge, which is made by dissolving salts (KCl, KNO3, etc.) and agar in water and solidifying them in a glass U-shaped tube.
	Scanning Electrochemical Microscope	A microelectrode is used as a probe to scan the top and vicinity of the target sample. The probe current fluctuates in response to the shape, conductivity, and electrochemical properties of the sample surface. By visualizing and analyzing this fluctuation as a two-dimensional image, objective information can be obtained. The spatial resolution is dictated by the size of the probe and can range from tens of nanometers to sub-micrometers. It is promising to be used in a wide range of fields, such as corrosion, ion transfer in membranes, and the study of biomaterials.
	SCE	A saturated mercury chloride electrode. One of the reference electrodes.
	SECM	Abbreviation for Scanning Electro- Chemical Microscopy. A scanning electrochemical microscope.
	SHE	Abbreviation for standard hydrogen electrode . It is a ideal redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials, under a hydrogen gas 1atm in the hydrogen ion activity 1 mol/L solution. It is a basis for comparison with all other electrode reactions, hydrogen's standard electrode potential (E0) is declared to be zero volts at any temperature.
	Silver silver chloride electrode	One of the reference electrodes. An electrode in which the surface of a silver wire is covered with a silver chloride precipitate and immersed in an aqueous solution containing chloride ions.
	Solid-liquid interface	In electrochemistry, it refers to the interface between the electrode and the electrolyte solution. Generally, a double layer capacity is formed.
	Spherical diffusion	As the size of the electrode becomes smaller, diffusion not only increases in the direction perpendicular to the electrode (planar diffusion), but also in the direction from 0 to 180 degrees, and the transfer efficiency is improved. For microelectrodes, spherical diffusion is dominant over planar diffusion.
	SPR	Abbreviation for Surface Plasmon Resonance.
	Supporting electrolyte	In electrochemical measurement, the electrolyte is usually dissolved in the solution to be measured. This is called supporting electrolyte. The purpose is to give the solution electrical conductivity and to minimize the contribution of electrophoresis in mass transport so that diffusion is prioritized.
	Surface resistivity	The surface resistivity, ρs, ρs = Ω/□ or Ω/sq, is used to describe the resistivity that determines the resistance of very thin thin film materials such as ITO (about 20 nm to 200 nm). □ or sq is dimensionless (unlike the resistivity of the overall material ρb in Ω-cm). This is based on the idea that the surface resistance of an extremely thin film can ignore the contribution of the volume fraction of the film. Thus, the resistance is entirely determined by the shape of the surface. That is, the surface resistance = ρs × (L/W) (W is the width of the electrodes, L is the distance between the electrodes, and both W and L are dimensional in length, so ρs is in units of Ω/square □). That is, if the distance between the electrodes L is greater than the electrode width W, the surface resistance will be greater, and conversely, if the width W is greater than the distance between the electrodes L, the surface resistance will be less. It is the ratio of W to L that determines the surface resistance, not the size (on the other hand, in the case of the overall material, the electrode surface area S is used instead of W, so ρb is given in Ω-cm).
	Sweep	Control the change of electrode potential with time at different rates.
	SWV	Square wave voltammetry. Similar to DPV, but the pulse waveform is equidistant.
	Tafel plot	A graph of the logarithm of the absolute value of the electrolytic current against the potential . Generally, it corresponds to a steady polarization curve. It is used to analyze the reaction mechanism.
	Three-electrode method	A measurement method that combines three electrodes: a working electrode, a counter electrode and a reference electrode. This is a common method of electrochemical measurement.
	Voltage hollower	Hollower is a word that means to chase, and in ancient times it was used in the field of electronic circuit engineering, such as cathode hollower (era of vacuum tubes), emitter hollower (era of transistors), source hollower (era of FET), and so on. It is a thing. Mostly impedance conversion circuits are intended to convert high impedance to low impedance to facilitate signal handling. In the operational amplifier, the voltage hollower is a circuit whose purpose is to transmit the voltage to the subsequent stage without any change (distortion) (again, the purpose is impedance conversion).
	Voltammetry	Measure current under potential regulation (constant or sweep ).
	Voltamogram	The potential is plotted on the horizontal axis and the current is plotted on the vertical axis.
	Warburg Impedance	Impedance due to diffusion process. It often appears in the low frequency region, and as the frequency decreases on the Nyquist plot, it increases with an inclination of 45 degrees with respect to the actual axis.
	Working electrode	An electrode that causes an electrochemical reaction of the target object when electrochemical measurement is performed.

↑Back to top

TOP > Technical library > Fuel cell glossary

Laboratory Of Research & Development, BAS Inc.
Professor Noriyuki Watanabe

A-C      D-F      G-I      J-M      N-R      S-Z

A - C

	Vocabulary	Commentary
	AEM	Abbreviation for anion exchange membrane.It allows the transfer of OH-.
	AFC	Abbreviation for alkaline fuel cell. Alkaline fuel cell. Use an alkaline electrolyte. Carrier ions are hydroxide ion (OH-).
	Agromelate	An aggregate of carbon fine particles dispersed in PEMFC (nano-sized platinum fine particles are supported as catalysts on the surface). Its surface is covered with an electrolyte solution, and there is a hydrophobic part in which the reaction gas passage is partially intertwined in a maze.
	Alkaline fuel cell (AFC)	An alkaline electrolyte is used. Charge carrier ions are hydroxide ion (OH-). Since the oxygen reduction reaction is fast under alkaline conditions, it is possible to use other than Pt electrodes, but on the other hand, there are advantages and disadvantages that the presence of carbon dioxide gas is harmful. It was used in the Apollo program in the early 1960s and proved effective, but was later changed to PEMFC in the Gemini program. The electrolyte is a KOH or NaOH, and the ion that carries the charge is OH-. The difficulty is that the solubility of carbonate generated by the presence of carbon dioxide is low and it causes trouble. The electrode reaction is as follows. the cathodic reaction ½O2 + H2O + 2e → 2OH- the anodic reaction H2 + 2OH- → 2H2O + 2e the total reaction is H2 + ½O2 → H2O It differs from PEMFC in that water is generated on the anode side (in PEMFC, water is generated on the cathode side). OH- from the cathode to the anode, water moves from the anode to the cathode. The electrode activity is high under alkaline conditions, but the major weakness is that the system itself has low CO2 resistance.
	AMFC	Abbreviation for anion exchange membrane fuel cell. Alkaline fuel cell using an anion exchange membrane.
	Anode	An electrode on which an oxidation reaction occurs. Also called the negative electrode. Become a cathode.
	Catalyst poisoning	Impurities (carbon monoxide CO and sulfur) in the fuel bind to the active sites of the catalyst and the activity of the catalyst is lost.
	Cathode	An electrode on which a reduction reaction occurs. Also called the positive electrode.
	CHP	Abbreviation for combined heat and power. A mechanism to improve energy utilization efficiency by effectively utilizing the heat energy generated by power generation. Cogeneration. Also called cogeneration for short. Effectively applied in high temperature fuel cells (SOFC, MCFC and PAFC).
	CO resistance	Platinum electrodes are easily poisoned by CO. When poisoned, the catalytic activity decreases. This is called low CO tolerance.
	Cogeneration	CHP. A direction and mechanism that aims to improve efficiency through the effective use of power generation and the simultaneous generation of heat energy in an integrated manner. Also shortly called cogene. It is effectively applied in high-temperature fuel cells (SOFC, MCFC and PAFC).
	Crossover	In a DMFC, the fuel, methanol, permeates the solid electrolyte membrane from the anode electrode side to the oxygen (cathode) side. In general, it is the permeation of the fuel to the cathode side, causing a reduction in the electromotive force of the battery.

↑Back to top

D - F

	Vocabulary	Commentary
	DEFC	Abbreviation for direct ethanol fuel cell. A fuel cell that uses the fuel ethanol directly for the anodic oxidation reaction. The carrier ion is a proton. Use the same electrolyte membrane which used for PEMFC.
	DMFC	Abbreviation for direct methanol fuel cell. A fuel cell that uses the fuel methanol directly for the anodic oxidation reaction. The carrier ion is a proton. Use the same electrolyte membrane used for PEMFC.
	Electro-osmotic flow	In solid ion-exchange membrane types (PEMFC, DMFC, etc.), the movement of hydrated water as protons move.
	Energy capacity	The energy that can be obtained from fuel is expressed in terms of weight or volume unit. For example, J/g, Wh/g, Wh/L, kWh/g, kWh/L, etc. (J is joule, W is watt). W is work, h is time, and the product is energy. Also called energy density.
	EOR	Abbreviation for ethanol oxidation reaction. Direct ethanol Oxidation reaction of ethanol at the anode electrode of a fuel cell.
	Ethanol fuel cell (DEFC)	Under acidic conditions, the anodic reaction CH3CH2OH + 3H2O → 2CO2 + 12H+ + 12e the cathodic reaction 3O2 + 12H+ + 12e → 6H2O the total reaction CH3CH2OH + 3O2 → 2CO2 + 3H2O In fact, the reaction cannot be carried through to the end, only to the production of acetic acid and acetaldehyde (4e only). Under alkaline conditions, anodic reaction is CH3CH2OH + 12OH- → 2CO2 + 9H2O + 12e the cathodic reaction 3O2 + 12H+ + 12e → 6H2O the total reaction CH3CH2OH + 3O2 → 2CO2 + 3H2O In fact, the reaction cannot be carried through to the end, only to the production of acetic acid and acetaldehyde (4e only). Under alkaline conditions, anodic reaction is CH3CH2OH + 12OH- → 2CO2 + 9H2O + 12e cathodic reaction is 3O2 + 6H2O + 12e → 12OH- The total reaction CH3CH2OH + 3O2 → 2CO2 + 3H2O However, the current anode catalyst does not complete the above reaction, and just proceeds in below step. CH3CH2OH + 4OH- → CH3COOH + 3H2O + 4e
	Flooding	When water is generated at the cathode, such as in a PEMFC, a flooding condition in which water overflows to the extent that it blocks the gas diffusion pathway. This is why moisture management is so important.
	Fuel cell (FC)	A mechanism or device that converts chemical energy (internal energy of a substance) into electrical energy. A battery composed of a combination of an oxidation reaction of fuel (mainly hydrogen molecules; other methanol, ethanol, formic acid, etc.) that occurs on the anode (negative electrode) side and a reduction reaction of an oxidant (mainly oxygen molecules) that occurs on the cathode (positive electrode) side. The feature is that there is a possibility that the energy utilization efficiency can be increased compared to the heat engine.
	Fuel reforming	The conversion of oil, coal, natural gas, biogas, etc. into molecular hydrogen for fuel through catalysis and chemical reactions.

↑Back to top

G - I

	Vocabulary	Commentary
	Gas diffusion electrode (GDE)	In the case of PEMFC, a porous electrode composed of ultrafine particles of catalyst (platinum is a typical example) supported on carbon fine particles. It is believed that a microspace surrounded by a partially covered region of the hydrophilic electrolyte and a hydrophobic region that can serve as a passage for the gas (fuel and oxidant gas) forms an intricate structure. It has an interface where the fuel and oxidizer gas phases, catalysts, and electrodes come into contact. Carbon is responsible for electron conduction, and electrolyte is responsible for ionic conduction.
	GDE	Abbreviation for gas diffusion electrode. A gas diffusion electrode.
	Hydrogen pole	An electrode that causes the oxidation of hydrogen. Anode pole of fuel cell.
	Hydrogen storage	The method of storing hydrogen as fuel and the method of supplying hydrogen (including infrastructure) are major problems for the practical use of fuel cells. There are high-pressure tanks (cylinders), low-temperature liquefaction, occlusion in other compounds, compounding, etc., and the latter is currently being reported in an ongoing manner and mixed with truth.
	ICE	Abbreviation for internal combustion engine. Internal combustion engine. A machine that burns fuel to generate power as rotational energy. It often comes up in the story of fuel cells in comparison with fuel cells.
	Ion exchange membrane	The membrane used in PEMFC is a proton exchange cation exchange membrane. Since it is composed of a polymer membrane based on Teflon (with polyfluoroethylene as a skeleton) and having a sulfonic acid group in the side chain, hydrogen ions (protons) can carry charges. Recently, the development of alkaline and stable anion exchange membranes for alkaline batteries has become active.
	Ionomer	Soluble conductive polymer added as an electrolyte to facilitate the electrode reaction at the cathode and anode in PEMFC.

↑Back to top

J - M

	Vocabulary	Commentary
	LFFC	Abbreviation for laminar flow fuel cell. Microfluid fuel cell. Development as a small drive power source has recently become active.
	LSM	Abbreviation for lanthanum strontium manganite. Strontium-doped lanthanate manganate (LaMnO3). It is used for the positive electrode of SOFC as an electrode for oxygen reduction. It is an electronic conductor.
	MCFC	Abbreviation for molten carbonate fuel cell. The carrier ion is the carbonate ion (CO32-).
	MEA	Abbreviation for membrane electrode assembly. Membrane-electrode-complex. PEMFC, etc., in which a solid exchange membrane and a catalyst-electrode bonded to it are integrated.
	Methanol fuel cell (DMFC)	Use the same type of ion exchange membrane as that used in PEMFC (acid electrolyte) the cathodic reaction is 3/2O2 + 6H+ + 6e → 3H2O the anodic reaction is CH3OH + H2O → CO2 + 6H+ + 6e the total reaction is CH3OH + 3/2O2 → CO2 + 2H2O The drawbacks are the crossover of methanol and the slow reaction rate. Under alkaline electrolytes, the electrode reaction rate is high, but the presence and formation of carbon dioxide gas is a major drawback in producing carbonates with low solubility. For alkaline fuel cell using an anion exchange membrane the cathodic reaction is &frac32;O2 + 3H2O + 6e → 6OH- the total reaction is CH3OH + &frac32;O2 → CO2 + 2H2O
	Microfluid fuel cell	A small portable fuel cell that utilizes two microscale (anode side and cathode side) laminar flows. There is mixing by diffusion in the direction perpendicular to the laminar flow, but the idea is that if the effect of mixing does not reach the electrodes, there may be no exchange membrane. There is an advantage that the liquid property (pH, fuel, oxidant, etc.) of the flowing fluid can be freely selected according to the purpose.
	Molten carbonate fuel cell (MCFC)	Used at high temperatures (600 - 700 °C). The electrolyte (LiKCO3) is a hot liquid. The reactions at each electrode are the anodic side H2 + CO32- → H2O + CO2 + 2e the cathode side ½O2 + CO2 + 2e → CO32- the total reaction H2 + ½O2 → H2O is the same as other FCs. the charge-carrying ion is carbonate ion (CO32-). The anode is porous metallic nickel, and the cathode is porous nickel oxide (NiO).
	MOR	Abbreviation for methanol oxidation reaction. Direct methanol oxidation reaction at the anode electrode of a methanol fuel cell.

↑Back to top

N - R

	Vocabulary	Commentary
	Nafion membrane	It is a polymer with a tetrafluoroethylene skeleton, has sulfonic acid group, proton exchange ability, and electrical conductivity.
	ORR	Abbreviation for Oxygene Reduction Reaction. Oxygen reduction reaction that occurs at the positive electrode (cathode).
	Overvoltage	The potential difference that must be applied extra because the charge transfer is too slow at the equilibrium potential is called activation overvoltage (polarization). In addition, there are overvoltages caused by the moving speed of the active ingredient not being able to keep up, and overvoltages caused by ohm resistance. Polarization due to the oxygen reduction reaction at the cathode is generally large in fuel cells, and research is continuing to reduce this to obtain a highly active catalyst.
	Oxygen pole	An electrode that causes the reduction of oxygen in FC. It is the cathode electrode.
	ORR	Reduction of oxygen molecules at the cathode pole, a reaction involving four-electron reduction and cleavage of the oxygen-oxygen bond, which is a major reason for slow reaction rates and large overvoltages, leading to a decrease in the electromotive force. Also, the process of hydrogen peroxide formation occurs partially in the two-electron reduction limit. Hydrogen peroxide can damage the polymer electrolyte membrane, and it is desirable to minimize its formation. Platinum is currently the fastest catalyst for the reaction, but it is a rare and expensive precious metal. Alternative catalysts to platinum are being actively studied.
	PAFC	Abbreviation for phosphoric acid fuel cell. The carrier ion is a proton.
	Parasitic current	Current that does not contribute to the output flowing between different single cells due to the stack structure.
	PEFC	Abbreviation for polymer electrolyte fuel cell.
	PEMFC	Abbreviation for proton exchange membrane fuel cell or polymer electrolyte membrane fuel cell. Proton exchange polymer film type fuel cell. The carrier ion is a proton.
	Phosphate fuel cell (PAFC)	It is the most popular as a distributed portable and stationary fuel cell. Moderate temperature (150°C - 200°C). The charge carrier (H+) and electrode reaction are the same as the solid ion exchange membrane type.
	Polarization	The potential difference that must be applied because the charge transfer reaction is too slow is called the activation polarization. It is also called activation overvoltage. In addition, there is a transport polarization associated with diffusion transport and a resistive polarization caused by ohmic resistance.
	Polarization curve	A curve plotting cell voltage and current values. It shows a voltage drop due to activation polarization, transport polarization, resistance polarization, etc. The first and foremost measurement items required for fuel cell characteristics and performance evaluation.
	Porous electrode	It is used for the purpose of increasing the effective surface area of ​​the electrode. It is important to increase the surface area in order to increase the efficiency of electrode oxidation and reduction reactions. Make it porous for that. Also called a porous electrode. Carbon cloth, carbon fiber, etc. are used for the backbone.
	Proton conduction	In PEMFC and PAFC, the charge is carried by the proton.

↑Back to top

S - Z

	Vocabulary	Commentary
	SAFC	Abbreviation for solid alkaline fuel cell. Alkaline fuel cell that uses a polymer electrolyte membrane (anion exchange membrane). Recently, active research has been carried out to reduce the effects of carbon dioxide.
	SOFC	Abbreviation for solid oxide fuel cell. A fuel cell with solid oxide (zirconia and ceria; zirconium and cerium oxides) as the electrolyte. Highest temperature specification (750°C - 1000°C).
	Solid ion exchange membrane fuel cell	Proton exchange membrane type: PEMFC Polymer electrolyte type: PEFC Methanol fuel cell: DMFC The electrolyte is a Teflon-based solid ion exchange polymer membrane having a sulfonic acid group in the side chain (almost the same as PEMFC). The ion that carries the charge is a proton (H+). It is being studied as a power source for automobiles due to its features such as medium and low temperature operation, low temperature startup, and high energy capacity. the cathodic reaction ½O2 + 2H+ + 2e → H2O the anodic reaction H2 → 2H+ +2e However, hydrogen storage of fuel, replenishment, infrastructure development, etc. are still huge challenges.
	Solid oxide fuel cell (SOFC)	Used at high temperatures. Uses an oxygen ion-conducting solid electrolyte (YSZ), which is more stable than MCFCs in that it is solid and does not leak. The reactions at each electrodes are in the anodic side H2 + O2-  → H2O + 2e in the cathodic side ½O2 + 2e → O2-
	Stack	A laminated structure in which single cells are stacked to obtain the required electromotive voltage.
	TPB	Abbreviation for three phase boundary. A three-phase interface, a catalyst, a gas phase, and an interface where electrodes are in contact. In the case of SOFC, it means the interface where the three phases of Ni pole, YSZ, and gas phase meet, and it is the place where fuel oxidation proceeds efficiently.
	Water management	In the polymer electrolyte membrane type FC (PEMFC, AMFC, DMFC), water is generated on the cathode or anode side. Therefore, it may become excessive in water. Also, the conductivity of the membrane is highly dependent on the water content. Therefore, proper management of water content is important.
	YSZ	Abbreviation for yttrium stabilized zirconia. Zirconia stabilized by adding yttrium. A solid electrolyte used as an oxygen ion conductor at high temperatures. Due to the large bandgap, its electronic conductivity is negligible. Used for SOFC.

↑Back to top