The reaction pool should be used for in situ XRD characterization of photocatalytic reactions. The top of the pool body is equipped with a quartz light window, and the left and right sides of the pool body are equipped with polyimide windows, equipped with reference electrodes, counter electrodes, and working electrodes. In situ XRD testing can be carried out under different wavelengths of light and electrical conditions to obtain the structural changes of the material; The reaction tank can achieve aeration operation in the solution inside the reaction tank, and the product can be equipped with a temperature control system to accurately control the test temperature of the reaction tank.