Photocatalyst technology was first developed in Japan in the 1970s and has been widely used in various industries for over 10 years. In fact, Japan has been a leader in photocatalyst research and development, with many Japanese companies producing photocatalytic products for use in air purification, water treatment, and building materials. The use of photocatalytic coatings has become increasingly popular in recent years due to their ability to provide long-lasting protection against harmful substances in indoor environments.