【Basic Knowledge 9】What is a double layer? (Questionnaire with Prizes)

The interior of the particle is called the particle core; it generally carries a negative charge, forming a layer of negative ions (i.e., the potential ion layer). Outside this core, a layer of positive ions forms due to electrical attraction (the counterion layer, which includes the inactive ion layer and the diffusion layer). Together, these form a double layer: the first layer consists of ions that are adsorbed specifically on the surface, while the second layer is the diffusion layer, which is maintained by electrostatic forces.

The interior of the particle is generally charged negatively, forming a negative charge layer, while an external positive charge layer is formed due to the electrolyte solution, and this is known as the double layer. The first layer consists of ions adsorbed on the surface. The second layer is the diffusion layer, which relies on electrostatic adsorption.

When any two different phases come into contact, a potential is generated between them due to charge separation. Each phase possesses an excess charge; the magnitudes of these charges are equal, but their signs are opposite. The phases attract each other, resulting in a double layer.

Please explain what a double layer is When the mineral surface at the solid-liquid interface becomes charged, electrostatic forces cause it to attract ions with opposite charges from the aqueous solution, resulting in the formation of two layers with opposite charge signs on either side of the solid-liquid interface; this structure is known as the double layer.

Double-layer theory: The electrostatic forces of the gel core attract counterions in the solution to its surroundings. Due to the electrostatic attraction of the charged nuclei and the diffusion caused by the thermal motion of the counterions, as well as the hydration of the counterions by the solution, the concentration of counterions decreases gradually as the distance from the solid surface increases, following a Boltzmann distribution. The German scientist W. Nernst provided a good explanation for the mechanism underlying electrode potential. He believes that when a metal is inserted into its salt solution, the cations on the metal surface are affected by polar water molecules, and they tend to become solvated ions that enter the solution, leaving the electrons on the metal surface. The more reactive the metal and the lower the concentration of positive ions in the solution, the greater this tendency becomes. At the same time, the metal ions in the solution also tend to deposit on the metal surface; the higher the concentration of metal ions in the solution and the less reactive the metal, the greater this tendency is. Dynamic equilibrium is achieved when the rates of these two opposing processes, dissolution and deposition, are equal. When the tendency for metal to dissolve is greater than its tendency for metal ions to deposit, a negative charge layer forms on the metal surface, while the solution near the metal surface carries a positive charge, thus creating a \"double layer\". Conversely, if the tendency to deposit is greater than the tendency to dissolve, a positive charge layer is formed on the metal surface, while the solution near the metal carries a negative charge. When dissolution and deposition reach equilibrium, a double layer is formed, which generates a potential difference. This potential difference is known as the equilibrium electrode potential of the electrode, or alternatively, the reversible electrode potential. Metals have different levels of reactivity, and as a result their electrode potentials vary; therefore, the electrode potential can be used to measure a metal’s ability to lose electrons.

When any two different phases come into contact, a potential is generated between them due to charge separation. Each phase possesses an excess charge; the magnitudes of these charges are equal, but their signs are opposite. The phases attract each other, resulting in a double layer. 　　A potential exists at the metal-electrolyte interface of the electrode, which likewise gives rise to a double layer; its total thickness is generally around 0.2–20 nanometers. The metal phase of the electrode is a good conductor, with excess charge concentrated on the surface ； The electrolyte has high resistance, and the excess charge remains only partially adjacent to the phase interface, known as the compact double layer ； The remaining part is in a dispersed state, known as the diffuse double layer ； It was mistranslated as “diffusion layer”). The core step of the electrode reaction – the overpotential step (i.e., the activation step) – must take place within the tight layer, and the adsorption processes that affect the electrode reaction also occur in the double layer. Therefore, the study of the double layer structure is of great significance for both the theory and practice of electrochemistry. 　　The surface of the colloid nucleus is covered with a layer of ions, known as potential ions. Through electrostatic forces, these potential ion layers attract ions with opposite charges from the solution to the vicinity of the colloid nucleus. The ions that are attracted are called counterions; their total charge is equal in magnitude but opposite in sign to that of the potential ions. In this way, a so-called double layer is formed in the interphase region of the medium surrounding the gel core.

The interior of the particle is generally charged negatively, forming a negative charge layer, while the exterior of the particle has a positive charge layer formed due to the electrolyte solution; this is known as the double layer. The first layer consists of ions adsorbed on the surface. The second layer is the diffusion layer, which adheres through electrostatic forces.

Correct answer: When a metal is immersed in an electrolyte solution, the atoms on its surface interact with the polar water molecules and electrolyte ions in the solution, resulting in the formation of structures with opposite charges on the metal side and the solution side of the interface.