NOVELTY - Forming a graphene-based product comprises forming a solid phase, physical mixture comprising one or more graphite-based precursors and one or more solid phase reduction-expansion chemical agents consisting of urea or thiourea, and heating the physical mixture in an inert atmosphere at a temperature sufficient to thermally decompose the solid phase reduction-expansion chemical agent to produce a reducing gas and form a graphene-based product, where each of the graphite-based precursors comprises one or more of a graphite oxide, and/or an expandable graphite.    USE - The method is useful for forming a graphene-based product including a single graphene sheet, a stack of single graphene sheets and entangled single graphene sheets and forming free-standing graphene, where the graphene-based product comprises a nanosheet (all claimed) and is useful as an electrode of a supercapacitor, a battery, a fuel cell and a solar cell.    ADVANTAGE - The method is capable of simply, rapidly and economically forming the graphene-based product using simple equipment with high quality and yield, low oxygen contents, controlled amounts of nitrogen and/or other impurities and improved thermal conductivity, strength, stiffness and electrical properties. The graphene-based product has high surface area and high volume-to-weight ratio.    DETAILED DESCRIPTION - Forming a graphene-based product comprises: either (a) forming a solid phase, physical mixture comprising one or more graphite-based precursors and one or more solid phase reduction-expansion chemical agents consisting of urea or thiourea, and (b) heating the physical mixture in an inert atmosphere at a temperature sufficient to thermally decompose the solid phase reduction-expansion chemical agent to produce a reducing gas and form a graphene-based product, where each of the graphite-based precursors comprises one or more of a graphite oxide, and/or an expandable graphite; or (a1) forming a physical mixture by physically mixing graphite oxide with a reductive-expansion agent comprising urea, (b1) heating the physical mixture in an inert atmosphere at a heating temperature to form a free-standing graphene-based product, where the heating temperature is at or above a decomposition temperature of the reductive-expansion agent, and (c1) cooling the free-standing graphene-based product. An INDEPENDENT CLAIM is included for forming a free-standing graphene comprising the step (a1) as above per se, heating the physical mixture to form free-standing graphene, and cooling the free-standing graphene, where the free-standing graphene comprises graphene sheets.