Method for preparing graphene or carbon nanotubes by electrolyzing carbon dioxide

The invention belongs to the technical field of electrochemistry and batteries, and in particular, relates to a method for preparing graphene or carbon nanotubes by electrolyzing CO2. The method uses one or more halides as electrolytes, and uses alkali metal or alkaline earth metal oxides as capturing agents; a reactor with the electrolytes and the capturing agents is heated to 400-1000 DEG C; then, CO2 is filled in the electrolytes; oxide materials with electrical conductivity are used as inertia anodes; and metal or carbon materials are used as cathodes for electrolysis. Such carbon materials as graphene and carbon nanotubes can be obtained at the cathodes in electrolysis; oxygen is generated at the anodes; and electrolyzed cathode products are collected after such treatments as cleaning and drying. Molten salt, adopted by the method, has stronger capturing capacity for carbon dioxide, and can be recycled; the operation is simple; and the environment is friendly.