A part of an electronic or electrical device or equipment that is processed by a computer gong. It is used as the two terminals of input or output current in a conductive medium (solid, gas, vacuum or electrolyte solution). One pole of input current is called anode or positive pole, and the other pole of discharging current is called cathode or negative pole. There are various types of electrodes, such as cathode, anode, welding electrode, electric furnace electrode, etc.
In the battery, the electrode generally refers to the position where the redox reaction occurs with the electrolyte solution. The electrode can be divided into positive and negative. Generally, the positive electrode is the cathode, which obtains electrons and reacts with reduction. The negative electrode is the anode, which loses electrons and reacts with oxidation. The electrode can be metal or nonmetal. As long as it can exchange electrons with electrolyte solution, it is called electrode. The concept of electrode was put forward by M. Faraday in 1834 after the systematic electrolysis experiment. The original meaning only refers to the metal rod inserted in the electrohydraulic system to form the battery. The component of a battery, which consists of a series of phases in contact with each other. One end of the battery is an electronic conductor metal (including graphite) or a semiconductor, and the other end must be an ionic conductor electrolyte. The electrode with the simplest structure should consist of two phases and a phase interface, i.e., [metal electrohydraulic]. The electrode defined above in machining mechanical parts is also called “half cell”. The naming method is very complicated. Some are named according to the metal part of the electrode, such as copper electrode and platinum electrode; some are named according to the characteristic substances in the redox pair of electrode activity, such as calomel electrode and hydrogen electrode; some are named according to the shape of the metal part of the electrode, such as drop mercury electrode and rotary electrode; some are named according to the shape of the metal part of the electrode The function of the electrode is named. These names, such as reference electrode and sodium ion selective electrode (see ion selective electrode), are conventional. Any metal in contact with electrolyte will produce potential (potential), which is the most important characteristic property of electrode.
electrode
If there is a fast electron exchange of a single redox pair on the electrode interface, that is, there is a single electrode reaction with a large exchange current (see transition overpotential), this kind of electrode can quickly establish an electrochemical equilibrium, which is called reversible electrode. The potential energy of the reversible electrode is stable for a long time, and it has strong anti-interference ability and can be measured accurately. It is a necessary part of the reversible battery and the core part of the potential analysis measuring device. Reversible electrodes have the following types:
① Metal electrodes, such as copper electrodes (Fig. 2), are characterized by the fact that redox pairs can migrate across the phase interface.
② Redox electrodes, such as Pt | Fe, Fe electrode (Fig. 3), Pt | Mn, MnO 嬄 h electrode, etc. Its redox pair can not move across the electrode phase interface. The platinum pt of the electrode only indicates that the electrode metal is inert. It only provides a place for electron exchange. Any inert metal can be used in practical application.
electrode
③ The gas electrode is a component of redox pair, and the redox electrode when it is composed of gas (Fig. 4), such as hydrogen electrode (pt| h2| h), chlorine electrode (pt| Cl2 | CL), etc. In order to accelerate the equilibrium, platinum black is needed to be plated on platinum to increase the surface area and act as electrocatalysis.
electrode
④ One component of redox pair is insoluble salt or other solid phase. Therefore, Dongguan CNC machining center consists of three phases and two interfaces (Fig. 1). There is a single rapid transition process at each phase interface, such as calomel electrode (hg| Hg2Cl2 | CL) and mercury oxide electrode (Hg | HGO | oh). In the calomel electrode, the dissolution equilibrium of calomel and electrolyte is completely controlled by the higher concentration of CL in the electrolyte. The exchange rate of CL on the interface of Hg2Cl2 | is also very fast, so its electrode potential is very stable. It is the most commonly used reference electrode. Some books and periodicals call this kind of electrode the second type.
electrode
Membrane electrode a device for measuring the activity of specific ions in an electrohydraulic system (Fig. 5), such as a glass electrode or an ion selective electrode, using the permeability of the membrane to a single ion or the potential established by the ion exchange equilibrium between the membrane surface and the electrolyte (Fig. 5).
Chemically modified electrodes attach active groups and catalytic substances to the surface of electrode metals (including graphite and semiconductors) by adsorption, coating, polymerization, chemical reaction and other methods to make them have strong characteristic functions. This is a new development of electrode preparation methods since 1970s.
Single electrode and multiple electrode: if there is only one dominant electrode reaction on the metal electro-hydraulic interface of the electrode, it is a single electrode; if there is not only one electrode reaction, it is multi electrode. For example, there may be two kinds of electrode reactions on the zinc electrode (zn| ZnSO4 aqueous solution)
Zn─→Zn+2e ⑴
2H+2e─→H2 ⑵
electrode
However, due to the high Superpotential of hydrogen on the metal zinc, the rate of reaction (2) is too small, and the reaction (1) is dominant. The above zinc electrode is considered as a single electrode and is a typical reversible electrode. When the impure zinc is immersed in sulfuric acid, the reaction rate of (1) and (2) is fast, so [Zn | H2SO4] electrode is a double electrode, and its static potential can be judged according to the polarization curve and polarization law of reaction (1) and (2). Metal corrosion system is often a double electrode. Multiple electrodes cannot be reversible
In practical application, the studied electrode is called working electrode W, which is also called indicator electrode in electrochemical analysis. Its potential can be measured by two electrode measurement battery composed of reference electrode R. When the working electrode needs to be polarized, another auxiliary electrode (or corresponding electrode, represented by C) should be used to form a three electrode measuring battery system (Fig. 6)
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