Mn3O4-coated Bi5O7I-BiOI photocatalyst as well as preparation method and application thereof

The invention discloses a Mn3O4-coated Bi5O7I-BiOI photocatalyst and a preparation method and application thereof.The preparation method comprises the steps that bismuth salt is dissolved in a mixed solution formed by water and nitric acid, then a solution containing manganese salt is added into the solution, and a solution A is prepared; dissolving iodide in water to prepare a solution B; mixing the solution A and the solution B under a stirring condition to prepare a solution C; continuously adjusting the pH value of the solution C to 9-13 by using the alkali liquor under the stirring condition, and continuously and uniformly stirring to prepare a solution D; the molar ratio of the element I to the Bi in the solution C is 1: (1-4); and transferring the solution D into a reaction kettle, reacting for 16-28 hours at 160-200 DEG C, cooling to room temperature after the reaction is finished, centrifuging, washing and drying to obtain the heterojunction type Mn3O4-coated Bi5O7I-BiOI photocatalyst. According to t