Preparation method for one-step synthesis of rare-earth-doped potassium niobate photocatalyst, and application of rare-earth-doped potassium niobate photocatalyst

The invention provides a preparation method for one-step synthesis of a rare-earth-doped potassium niobate photocatalyst. The preparation method is characterized by comprising the following steps: (a) dissolving a rare-earth salt, potassium hydroxide and niobium oxide in water, and stirring and uniformly mixing to form a suspension; (b) transferring the suspension to a high-pressure reaction kettle for reaction; (3) washing, drying and grinding powder obtained after reaction, wherein the rare-earth salt is one of Sm(NO3)3.6H2O, SmCl3.6H2O, Sm(NO3)3.6H2O and GdCl3.xH2O; the doping proportion of the rare-earth salt is 0.1-1% of the molar weight of niobium oxide; molar weight of potassium hydroxide is 4-5 times of that of niobium oxide. Through adding of rare-earth salt, the photocatalytic activity can be remarkably improved. The preparation method is simple in process and easy to implement and popularize, and the prepared doped catalyst has relatively good photocatalytic performance.