A precious metal catalyst is a precious metal material that changes the rate of chemical reaction and does not itself participate in the final product of the reaction. Almost all precious metals can be used as catalysts, but platinum, palladium, rhodium, silver, ruthenium, etc. are commonly used, among which platinum and rhodium are the most widely used. Their d electron orbitals are not filled, the surface is easy to adsorb reactants, and the strength is moderate, which is conducive to the formation of intermediate "active compounds", has high catalytic activity, and also has comprehensive excellent properties such as high temperature resistance, oxidation resistance and corrosion resistance. Become the most important catalyst material.