In this research, nanocomposite containing reduced graphene oxide nanosheets (RGO) and trimetallic three-dimensional (3D) Pt-Pd-Co porous nanostructures was fabricated by galvanic replacement technique. First, GO suspension was drop-casted on the electrode surface, then GO film reduction was carried out by cycling the potential in negative direction to form the RGO on GCE (RGO/GCE). Then, electrodeposition of the cobalt nanoparticles (CoNPs) as sacrificial seeds was performed onto the RGO/GCE by using cyclic voltammetry. Afterward, Pt-Pd-Co 3D porous nanostructures fabrication occurs through galvanic replacement method based on a spontaneous redox process between CoNPs and solution...