The catalytic converter is a device used in automobiles to purify automobile exhaust. The reason why it is called catalytic converter is that it contains three precious metals: platinum (Pt), rhodium (Rh), and palladium (Pd), so it is called "catalytic converter ". Its role in automobiles is mainly to oxidize and reduce the main pollutants in automobile exhaust: carbon monoxide, hydrocarbons and nitrogen oxides to generate harmless carbon dioxide, nitrogen and water to achieve purification results.

with the arrival of March 2021, the annual spring online shopping peak was spreading quietly. On the large international online shopping platform "Alibaba", a "unique" product appeared on the front page of the homepage.