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Catalysis is one of the concepts frequently used in middle school chemistry and college chemistry. This article will discuss the emergence of the concept of catalysis and people's understanding of it at different stages. The concept of catalysis could not have arisen before the concepts of chemical change and chemical reactions existed. The concept of chemical change is based on the law of conservation of mass proposed by Lavoisier and the concept of chemical elements. Therefore, although catalytic phenomena were known as early as the 18th century, it was not possible at that time to consider them as a distinct category of reactions. The first person to clearly recognize the phenomenon of catalysis was G.S.C. Kirchoff, who in 1814 studied the reaction of acid-catalyzed hydrolysis of starch into glucose, although the term \"catalysis\" did not exist at that time. Not long after, in 1814, Sir Humphry Davy discovered the oxidation of gas over platinum, a multiphase catalytic reaction, and he described this reaction process in detail. For some time thereafter, some people continued to study the oxidation reactions on platinum. Thenard discovered that a small amount of a certain substance present in the solution or as a separate phase could accelerate the decomposition of hydrogen peroxide. In 1834, Faraday published a famous paper on the reaction of hydrogen and oxygen on platinum foil; in it he characterized and evaluated the catalytic activity, deactivation, poisoning, and activation of catalysts, while also conducting some studies on reaction kinetics. Although the kinetic measurements are rough, some important conclusions can still be drawn from them. He believes that hydrogen and oxygen gather on the platinum surface and come close to each other, thereby causing the reaction to occur. Platinum itself cannot bind any particles; its role is merely to attract the reactants closely around it. However, at that time it was not yet known that hydrogen and oxygen were diatomic molecules, even though many scientists had already accepted Dalton’s atomic theory. In the scientific era, it was Berzelius who in 1836 first used the term \"catalysis\" to describe various observations regarding trace substances that do not get consumed themselves but are able to influence the rate of reactions. The examples cited by Becherius include the acid-catalyzed hydrolysis of starch into glucose, the effect of metal ions on the decomposition of hydrogen peroxide, and the role of platinum in the reaction between hydrogen and oxygen. The word catalysis is composed of two Greek words; the prefix cata- means descent, while the verb ly means to divide or break apart. Becherius probably used the term “catalysis” to denote the removal of the forces that normally hinder molecular reactions. At that time, the chemical structures of reactants, products, and catalysts were not known; the atomic-molecular theory had not yet been fully established, the nature of chemical bonds and the concept of energy were unclear, and electrons had not yet been discovered. Therefore, Berzelius could not provide a reasonable explanation for the nature of catalysis. He believes that catalysis is not a chemical process. He introduced the concept of catalysis to explain catalytic phenomena. All molecules possess a certain residual affinity. There is no evidence to suggest that, in any substance, the complete attractive forces of its elements are satisfied; a catalyst simply enables it to add its own attractive forces to any other substance. For example, in the reaction between hydrogen and oxygen on platinum, platinum concentrates oxygen using its surface attractive forces and then supplies it to the hydrogen in a concentrated state, resulting in combination. Bechereau considered catalysis to be a physical process. Not everyone accepted Becherius’ views; in 1838, De. Pull. De la Rive proposed that on the surface of platinum, the catalytic reaction between hydrogen and oxygen involves a process in which platinum is first oxidized by oxygen, and then this oxide is reduced by hydrogen. He believed it was unnecessary to rely on the mysterious catalytic force proposed by Becherius to explain this reaction. The great chemist Justus von Liebig also opposed Berzelius’s views. In a letter to his friend Wüller, he wrote: \"Do you know that in Germany there are some fools who have written books in which they use the term ‘catalysis’ without any verification, stuffing these concepts into our children’s minds.\" Don’t you think the entire concept of catalysis is wrong? ” There are other theoretical explanations related to the phenomenon of catalytic reactions; for example, in the 1820s, Pfaff proposed that catalyst platinum has a low specific heat, which allows it to be easily heated to a red-hot state, thereby igniting the hydrogen-oxygen mixture. However, this hypothesis could not explain the selectivity of the catalyst, and thus it was quickly abandoned. In 1858, organic chemist Kekulé proposed that the role of a catalyst is to bring reactant particles closer together, thereby weakening the bonds between the atoms in the reactants themselves. B. Green proposed that catalysts act as carriers for reactant particles. J. Mercer, on the other hand, views catalysis as an expression of weak chemical affinity. In short, during this period, some catalytic phenomena were discovered and the concept of catalysis was proposed; however, its essence remained quite unclear, which led to certain issues in defining catalysis. F.W. Ostwald, the father of physical chemistry, proposed definitions of catalysts and catalysis from a modern perspective: \"A substance that can change the rate of a chemical reaction without itself forming the final products of that reaction is called a catalyst.\" ”He listed 4 types of catalysis: (1) catalysis of segregation in supersaturated systems, (2) catalysis in homogeneous mixtures ； (3) Heterogeneous catalysis (4) Enzymatic catalysis. In 1881, at the age of 28, Ostwald was appointed as a professor of chemistry at the Technical University of Leipzig, where he began a series of studies titled “Research on Chemical Kinetics”. He first conducted research on the acid-catalyzed saponification of acetamide and the hydrolysis of esters, and then carried out experiments on the conversion of sucrose in the presence of various acids. These studies laid the foundation for his subsequent fruitful achievements in catalysis research during his time in Leipzig. In 1887, Ostwald went to the University of Leipzig, where he, together with Arrhenius and van’t Hoff, founded physical chemistry. He summarized many experimental results and defined catalysis based on the laws of thermodynamics. Nearly a century has passed since then, and its core ideas have remained largely unchanged. He also published A History of the Theory of Contact Action (1898), in which he explored the origins and development of catalysis. A clearer formulation of the entire issue is found in the 1901 lecture “On Catalysis,” which was published as a booklet the following year. In 1909, Ostwald was awarded the Nobel Prize in Chemistry for his outstanding contributions to the study of catalysis, chemical equilibrium, and reaction rates. He was the first scientist to win a Nobel Prize in catalysis. However, Ostwald’s understanding of the nature of catalysis was quite different from modern views. Similar to Faraday, Ostwald believed that the role of a catalyst was merely to concentrate the reactants on its surface. Thank you to the readers for their recommendations! It was Irving Langmuir’s many groundbreaking studies that raised our understanding of the nature of catalysis to a new scientific level. In 1909, Langmuir was working on tungsten filaments at General Electric. He pioneered the study of surface physicochemistry by measuring the adsorption of various gases at low pressures on tungsten, platinum, and other metals. His research achievements mainly include the modern concept of chemical adsorption and the Langmuir adsorption isotherm. The ideas contained in Langmuir’s 4 articles formed the basis for understanding the mechanism of catalysis. Langmuir measured the rate of molecular adsorption of various gases on clean metals; from the gas pressure, he calculated the number of collisions between gas molecules and the surface per second, and then determined the collision fraction, which led to the derivation of the collision fraction for chemical adsorption (the adsorption coefficient). Langmuir measured the reaction rates of H2 and O2, as well as CO and O2, on platinum, determined their kinetic orders, and proposed reaction mechanisms based on the kinetic data. Langmuir found that H2 and O2 adsorb dissociatively on the platinum surface, with chemical adsorption being limited to a single molecular layer. In 1912, Schrödinger accurately determined the atomic structure of platinum and some other metals, which enabled Langmuir to describe catalytic active centers in detail for the first time. Langmuir believed that the surface atoms of platinum must be chemically unsaturated in order to be able to react with gas-phase molecules. In terms of the current description, it means that the platinum atoms on the surface are not coordinatively saturated. The concept now known as the Lewis-Langmuir bonding pair allows Langmuir to go far beyond the scope of problems that could be explained by the old notion of affinity. From his kinetic measurements, Langmuir also deduced the oxidation process of CO: first, the dissociative adsorption of oxygen, followed by the combination of non-adsorbed CO with adsorbed oxygen atoms. He ruled out a chemical reaction between the adsorbed CO and surface oxygen atoms. Current research work by Ertl in Munich shows that, at least at very low pressures, the reaction involves the reaction of adsorbed CO with surface oxygen atoms. In other words, Langmuir rejected what is now often referred to as the Langmuir-Hinshelwood mechanism, and adopted the Pideal-Eley mechanism. At normal pressure, Langmuir is correct. In one of his papers presented to the Faraday Society, Langmuir said: “Most scientists feel that the nature of catalysis is now almost as mysterious as it was in the Faraday era.” However, as our knowledge of the atomic and molecular structure of the solid catalysts that make up them continues to grow, we will gradually gain a clear understanding of this surface reaction mechanism. ” Langmuir’s research work led chemists to completely abandon the concept of catalysis. The study of the adsorption of various gases on metal surfaces enhanced the understanding of heterogeneous catalysis and its mechanisms, which led to the awarding of the Nobel Prize in Chemistry in 1932. Starting from the 1950s, infrared, nuclear magnetic resonance, paramagnetic, Mössbauer spectroscopy, and some surface energy spectroscopies began to be applied to the study of the nature of catalysis. These techniques can provide some information on the structure of the adsorbate and on the nature of the catalytic active centers. The establishment of the modern concept of catalysis went through a long process. It is believed that as modern instruments advance and physical-chemical theories continue to evolve, our understanding of catalysis will also be continually refined.