In 1663, Otto von Guericke, a German physicist, created the first generator, which generated static electricity through friction in the machine. This generator is made by putting a huge sulfur ball into a glass ball and fixing it on a shaft. Rotate the ball by shaking the crankshaft. When a gasket rubs against the rotating ball, an electrostatic spark will be generated. The sphere can be disassembled and used as a source of electrical tests.
In the middle of the 17th century, French chemist Charles Franç Ois de Cisternay du Fay discovered two different kinds of static electricity, that is, the same kind of charges repel each other and the different kinds of charges attract each other. Du Fay announced that electricity is composed of two different liquids: "vitreous" (Latin for "glass"), or positive electricity; And "resinous", or negative. This is the double liquid theory of electricity, which was rejected by Benjamin Franklin's single liquid theory in the late 17th century.
In 1781, Charles Augustin de Coulomb developed the law of electrostatic attraction in the process of trying to study the law of charge repulsion proposed by British scientist Joseph Priestley.
In 1791, Gavani published the "animal electricity" phenomenon that metal can make frog leg muscles shrink, which is generally believed to be the origin of electrochemistry. In 1799, based on the work of Gavani, Volta invented the "electric stack" composed of different metal sheets and wet paper, which is now called "Volta stack". This is the prototype of chemical power supply. stay DC motor Before the invention, various chemical power sources were the only ones that could provide constant current. 1834 Faraday's law of electrolysis The discovery of β - cyclodextrin lays a quantitative foundation for electrochemistry. In the second half of the 19th century, the work of Helmholtz and Gibbs gave a clear thermodynamic meaning to the "starting power" (now called "electromotive force") of the battery; In 1889, Nernst used thermodynamics to derive the relationship between the concentration of substances involved in electrode reaction and the electrode potential nernst equation ; In 1923, Debye and Shockel put forward the widely accepted theory of strong electrolyte dilute solution electrostatic, which greatly promoted the development of electrochemical theory and experimental methods. Since the 1940s, the application and development of electrochemical transient technology and the combination of electrochemical methods with optical and surface technologies have enabled people to study rapid and complex electrode reactions and provide information on molecules at the electrode interface. Electrochemistry has always been an active branch of physical chemistry. Its development and the development of solid physics, catalysis, life science and other disciplines promote and penetrate each other.
Among many branches of physical chemistry, electrochemistry is the only discipline based on large industry. Its applications mainly include: electrolysis industry, in which chlor alkali industry is the inorganic basic industry next only to synthetic ammonia and sulfuric acid; The smelting of light metals such as aluminum and sodium, and the refining of copper and zinc also use electrolysis; The mechanical industry uses electroplating, electropolishing, electrophoretic painting, etc. to complete the surface finishing of components; For environmental protection, cyanide ion, chromium ion and other pollutants can be removed by electrodialysis; Chemical power supply; Corrosion prevention of metals, most of which are electrochemical corrosion Problems; Many life phenomena such as muscle movement and nerve information transmission are related to electrochemical mechanism. Various kinds of electrochemical principles Electrochemical analysis It has become an indispensable means of laboratory and industrial monitoring. [1] Battery It is composed of two electrodes and the electrolyte between them, so the research content of electrochemical power generation should include the research of electrolyte, namely electrolyte science, including the conductivity of electrolyte, the transport property of ions, the equilibrium property of ions participating in the reaction, etc electrolyte solution The physical and chemical research of Primary battery It makes use of the difference in the metallicity between the two electrodes to generate the potential difference, so as to make the electrons flow and generate the current. Also known as non battery, it is a kind of electrochemical battery. Its electrochemical reaction cannot be reversed, that is, it can only convert chemical energy into electrical energy. In short, it cannot re store electricity, as opposed to battery. The primary battery is a device that converts chemical energy into electrical energy. Therefore, by definition, ordinary dry cells and fuel cells can be called primary cells.
Basic conditions of primary battery
1. Insert two kinds of metals with different activity (i.e., one is active metal and the other is inactive metal), or an inert electrode such as metal and graphite (Pt and graphite are inert electrodes, that is, they will not lose electrons) into the electrolyte solution.
2. Connect with wires and insert them into electrolyte solution to form a closed circuit.
3. Spontaneous Redox reaction 。 Operating principle of primary battery
The primary battery is to generate current in the external circuit by the oxidation reaction and reduction reaction of a spontaneous redox reaction on the negative pole and positive pole of the primary battery respectively. [2]
Judgment of electrode of primary battery
Negative pole: the pole from which electrons flow; The pole where the oxidation reaction occurs; One pole of highly active metal.
Positive pole: the pole into which electrons flow; The pole where the reduction reaction occurs; One pole of a relatively inactive metal or other conductor.
In the primary battery, the external circuit is electrically conductive, and the electrolyte solution is ionic conductive.
Determination of primary battery
(1) First, analyze whether there is an external circuit. If there is an external power supply, it is the electrolytic cell, and if there is no external power supply, it may be the primary battery; Then, according to the analysis and judgment of the formation conditions of the primary battery, it is mainly "four looks":
Look at the electrode -- the two poles are conductors with different activity (the electrode of fuel cell is generally inert);
Look at the solution -- the two poles are inserted into the solution;
Look at the circuit - form a closed circuit or direct contact between two poles;
See the essence -- whether there is oxidation-reduction reaction.
(2) When multiple cells are connected, but there is no external power supply, the cell with the greatest difference in activity between the two poles is the primary battery, and the other cells can be regarded as electrolytic cells. [3]
Corrosion of galvanic cell principle
The comparison between chemical corrosion and electrochemical corrosion is shown in Figure 1. [4]
Fig. 1 Comparison between chemical corrosion and electrochemical corrosion Operating principle of fuel cell
To describe it in a simple sentence, we can say that a fuel cell is a combination of fuel and oxygen A device that converts chemical energy into electrical energy. Like a battery, it has positive and negative poles. The ordinary battery can only store electric energy, while its energy source continuously generates electricity. Therefore, the fuel cell is similar to the internal combustion generator set, but its operating temperature is much lower, and there are few or no rotating parts. Composition of fuel cell system
In order to meet the power demand of motors or other electrical appliances, it is not only enough to have a battery stack. As a fuel cell system, it must have many other components, such as fuel supply, water balance control, output power adjustment, temperature and pressure measurement and control and other parameters. Without the above components, it is impossible for the fuel cell to generate usable electric energy.
(1) Pure hydrogen or hydrogen rich fuel supply system;
(2) Hydrogen rich fuel reforming system;
(3) Hydrogen purification system;
(4) Hydrogen storage system;
(5) Fuel cell stack;
(6) Output energy control regulator;
(7) Electric energy memory;
(8) Temperature control system;
Advantages of fuel cell system
（1） Fuel cell power generation It does not need an internal combustion engine, which means that unlike ordinary generating sets, this kind of generating equipment has low noise, low vibration, and almost no air pollution or greenhouse gas emissions. (2) Low power consumption equipment such as mobile phones, portable computers, etc., and fuel cells used in non emission vehicles do not require relatively long cycle charging time like ordinary batteries. In addition, the fuel of the fuel cell can be stored in the memory outside the body, so that the size of the memory can be adjusted according to the use requirements to adjust the use time.
(3) The use of fuel cells can reduce the investment and operation costs of traditional generator sets, transmission systems and distribution systems, and can also reduce the losses in the process of power generation, transmission and distribution.
(4) The efficiency of fuel cell power generation is much higher than that of traditional generators, and the energy conversion efficiency of fuel units is 2-4 times higher than that of traditional generators. [5]
