The birth of the three-way catalyst is inextricably linked to the development of the automotive and petrochemical industries. As it was discovered that the increase in octane value could effectively reduce engine knocking, the gasoline label was continuously improved.  However, with the increase in combustion temperature in the cylinder, new pollutants - nitrogen oxides - began to appear in the exhaust gas. The 1943 Los Angeles photochemical smog event began to raise people's awareness of automobile exhaust pollution problems.  In order to solve this problem, researchers have been racking their brains, and finally they concluded that it is necessary to eliminate pollutants at the source. In 1952, Eugene Houdry, a Frenchman, developed a catalytic converter and registered a patent. In 1975, the US regulations stipulated that all gasoline vehicles must be equipped with catalytic converters. However, at that time, the catalytic converters were still binary, with the main components being metal platinum and palladium, which could catalyze and oxidize carbon monoxide and unburned hydrocarbons in automobile exhaust into carbon dioxide and water, but nitrogen oxides remained "free". In 1981, researchers introduced metal rhodium into the catalyst, which could remove nitrogen oxides from the exhaust gas, and the three-way catalyst was officially born. After the birth of the three-way catalyst, countries have added provisions for installing three-way catalysis on gasoline vehicles in automobile emission regulations, so the three-way catalyst has truly become popular.