Ternary composite photocatalyst containing heteropoly acid as well as preparation method and application of ternary composite photocatalyst

The invention discloses a ternary composite photocatalyst containing heteropoly acid as well as a preparation method and application of the ternary composite photocatalyst. The ternary composite photocatalyst is prepared from raw materials including heteropoly acid, cadmium acetate, g-C3N4 and thiourea in a one-pot mode through a hydrothermal method. The series of photocatalysts can catalytically degrade organic dye rhodamine B under the radiation of visible light and catalyze lignin to convert vanillin under the radiation of visible light, and the series of photocatalysts are good in stability and can be repeatedly used. The photocatalyst is prepared by a one-pot method, and the operation is simple and controllable; the catalyst has excellent photocatalytic performance under visible light; rhodamine B can be efficiently degraded under visible light and mineralized, so that the resource cost is greatly saved, and meanwhile, secondary pollution is avoided; in addition, the effect of catalyzing conversion of th