▎ 摘　　要

NOVELTY - Preparing a graphene sheet, comprises: disposing a graphitizing catalyst upon a substrate; disposing a polymer on the graphitizing catalyst; and heat-treating the polymer on the graphitizing catalyst to form a graphene sheet. USE - The method is useful for preparing graphene sheet which is useful in hydrogen storage medium, electrical device (all claimed), a membrane and an optical fiber, a flexible transparent electrode, solar cells and display devices. ADVANTAGE - The method provides large-area graphene sheet with: desired thickness in economical manner and efficiently controls thickness of graphene sheet; excellent conductivity, flexibility and high uniformity; and desired conductivity from small amount of electrical energy and improved light penetration. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) the graphene sheet comprising polycyclic aromatic molecules having many carbon atoms that are covalently bounded to each other, where the graphene sheet has 1-300 layers and a width and length each of greater than or equal to 1 mm; and (2) a graphene substrate comprising a substrate and the a graphene sheet formed on the substrate.