Disclosed herein is a novel polycationic peptide conjugated graphene-metal nanoeomoposite comprising graphene, metal  nanoparticles and polycationic peptide. The compound characterized by black to reddish brown in color, sparingly soluble in water as  well as pular solvents, but insoluble in non-polar solvents. The compound exhibits stability at wide pH (2.0-10.0) and temperature (4- 40 °C) range and also carries net positive charge at pH values <7.0. The process of preparation of a novel polycationic peptide  conjugated graphene-metal nanoeomoposite involves synthesis of graphene-metal nanocomposite, followed by amine modification of  the nanocomposite, which is then covalently bound with polycationic peptide. The compound has a combination of catalytic,  antibacterial, anti-fouling and adsorptive properties. The compound demonstrates catalytic activities in hydrogenation reaction of  pnitrophenol, and oxidation of orthophenyldiaminc, and monosaccharides, and therefore can be used for synthesis of small organic  molecules. The compound can also be used for separation and removal cations, anions, and microorganisms from water.