In this work, Pd nanoparticles/porous graphene (Pd/PGR) is prepared by simultaneous reduction of graphene oxide (GO) and Pd precursor in sodium borohydride (NaBH4) solutions at the electrode surface. In this preparation, the positively charged ZnO with high isoelectric point is used as templates for the adsorption of negatively charged GO in water. Then, the poly(diallyldimethylammonium chloride) (PDDA) is added into the ZnO/GO through the electrostatic interaction between the negative charge of GO and positive charge of PDDA. Subsequently, PDDA/ZnO/GO is employed as a support material for the adsorption of chloropalladic acid ions (PdCl42-), via the self-assembly between the negative Pd precursor and positively charged functional groups of PDDA. One-step-reduction of Pd precursor/PDDA/ZnO/GO in NaBH4 solutions and the subsequent removal of the ZnO produce Pd/PDDA/PGR with a porous structure at the electrode surface. With a porous morphology and large surface area for both efficient exposure of Pd nanoparticles and enhanced electrolyte-reactant diffusion, a sensitive enzymeless sensor of hydrogen peroxide (H2O2) is constructed. Compared with the nonporous Pd/PDDA/GR, the Pd/PDDA/PGR displays high electrocatalytic activity towards H2O2, exhibiting a high sensitivity of 57.7 mu A mM(-1) and low detection limit of 0.9 mu M towards the reduction of H2O2. The improved activity and simple preparation method makes Pd/PDDA/PGR promising for being developed as an attractive robust and new electrode material for electrochemical sensor and biosensor fabrication. (C) 2016 Elsevier B.V. All rights reserved.