As the name suggests, photocatalyst requires light as a catalyst to accelerate the reaction. It is normal for all photocatalysts on the market to require ultraviolet irradiation. But as far as I know, Anhui Yezi Environmental Protection has a patent on the photocatalyst. It can make the photocatalyst react with formaldehyde in natural light or no light environment. The effect is not bad, but it is definitely better to have ultraviolet light. Hope it’s useful to you