▎ 摘　　要

NOVELTY - A carbon-based composite comprises nanosheet-like graphene oxide or its reduced product, and carbon quantum dots. USE - Carbon-based composite is used in composition for oxygen reduction catalyst ink used in electrode (all claimed) e.g. air cathode for metal-air cell and polymer electrolyte fuel cell. ADVANTAGE - The carbon-based composite can be prepared by simple and economical process without using platinum, and has excellent oxygen reduction characteristics. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) manufacture of the carbon-based composite, which involves generating carbon quantum dots by heating an aqueous solution containing a carbon source compound and a nitrogen source compound at a temperature equal to or higher than the boiling point of water, mixing the obtained carbon quantum dots and nanosheet-like graphene oxide in an aqueous solvent, and drying to remove the solvent from the resulting mixture; (2) composition, which comprises the composite and a conductive support agent; and (3) catalyst ink, which comprises the composition, a binder, and a solvent.