▎ 摘　　要

NOVELTY - The preparation method of graphene involves mixing lignin with aqueous solution, adding catalyst precursor into aqueous solution, immersing pretreated substrate in lignin solution, taking out, soaking in ultra-pure water, washing, drying, immersing in catalyst precursor solution, taking out, soaking in ultra pure water, washing, low temperature drying to obtain a layer of lignin polyelectrolyte and catalyst precursor self-assembled film, repeating immersing in lignin solution, soaking in ultra-pure water, washing with ultrapure water, and impregnating catalyst precursor solution. USE - Preparation method of graphene (claimed). ADVANTAGE - The method enables preparation of graphene with controllable number of layers and considerable yield, by simple and convenient process. DETAILED DESCRIPTION - The preparation method of graphene involves (1) mixing lignin with certain concentration of aqueous solution, and adding a certain amount of catalyst precursor into the aqueous solution, where the catalyst precursor is iron(III) chloride, iron(II) sulfate heptahydrate, iron(III) nitrate nonahydrate, copper sulfate pentahydrate, cobalt nitrate, and nickel(II) sulfate hexahydrate, (2) immersing the pretreated substrate in the lignin solution for a period of time, taking out, soaking in ultra-pure water for a period of time, washing with ultra-pure water several times, drying at 10-25 degrees C, immersing in catalyst precursor solution for a period of time, taking out, soaking in ultra pure water, and washing several times, low temperature drying at 10-25 degrees C to obtain a layer of lignin polyelectrolyte and catalyst precursor self-assembled film, repeating immersing in lignin solution, soaking in ultra-pure water, washing with ultrapure water, impregnating the catalyst precursor solution, soaking in ultra-pure water, washing with ultra-pure water to obtain self-assembled film with controllable layer, and (3) placing the sample obtained in step (2) in a vacuum tubular furnace, introducing hydrogen/argon mixed gas at a constant rate, heating at target temperature and at certain speed, reducing the furnace temperature in a double temperature zone to room temperature, taking out the sample, removing catalyst by acid immersion, washing several times, and vacuum drying.