▎ 摘　　要

NOVELTY - Preparing onion carbon/graphene composite aerogel involves disperse in deionized water to obtain a dispersion, adding onion carbon to disperse uniformly, addinge reducing agent ammonium citrate, hydrothermal reaction to complete self-assembly to form onion carbon/graphene composite gel, performing dialysis, and freeze-drying to obtain three-dimensional network structure of onion carbon/graphene composite aerogel supported by onion carbon and graphene sheets. USE - Method for preparing onion carbon/graphene composite aerogel used as a flame retardant (claimed). ADVANTAGE - The method enables to preparing onion carbon/graphene composite aerogel, which has ultra-low density and good mechanical properties, has low thermal conductivity and excellent flame-retardant heat insulation performance.