Method for degrading lignin using visible-light response composite catalyst

The invention discloses a method for degrading lignin using a visible-light response composite catalyst. The method comprises the following steps: attaching a visible-light response photosensitizer to the surface of a nano catalyst; and through interfacial electron transfer action, transferring the excited electrons generated by a visible-light excitation composite catalyst to the conduction band of the nano catalyst to form active substances such as superoxide radicals or superoxide anions on the surface of the nano catalyst, wherein the active substances generate an activating reaction with lignin to remove methoxy group in the phenyl propane structure unit of lignin and increase the hydroxyl value of lignin. The method disclosed by the invention has the following advantages: the benzene ring retention rate of the activation product is high; compared with the high-pressure catalytic hydrogenation degrading method, the technology can be performed at normal temperature under normal pressure, and the equipment cost as well as the energy consumption in the degrading process are reduced; and compared with the lignin enzymolysis method, the production cycle of the technology is short, and the cost is low. The highest content of total hydroxyl of the alkali lignin activation product can be increased by about 147wt% over the alkali lignin before degradation.