The   present   study   is   an   attempt   to   prepare   new   nanocomposites   based   on   Pt-modified [PW11NiO39] 5
@reduced  graphene  oxide  (rGO)  and  Pt-modified  [PW11NiO39] 5
@multiwall  carbon nanotubes (CNT). For this purpose, poly diallyldimethylammonium chloride (PDDA) modified-rGO and PDDA-CNT   are   prepared,   the   surfaces   of   which   are   then   decorated   with   polyoxometalate ([PW11NiO39] 5
). Finally, [PW11NiO39] 5
@PDDA-rGO and [PW11NiO39] 5
@PDDA-CNT are decorated with platinum  nanoparticles  to  fabricate  [PW11Pt e NiO39] @PDDA-CNT/GCE  and  [PW11Pt e NiO39] e @PDDA-rGO/GCE. The amounts of the noble metal required for the modification of the electrodes is reduced by using the replacement reaction, as a simple and effective method. Polarization measurement, cyclic voltammetry and electrochemical impedance spectroscopy are used to investigate the electrochemical properties   of   [PW11Pt e NiO39] @PDDA-rGO   and   [PW11Pt e Nio] @PDDA-CNT   in   a   solution   of 0.5 mol L
1 H2SO4. The nanocomposites are then characterized in detail using scanning electron microscopy,  transmission  electron  microscopy,  energy  dispersive  X-ray  spectroscopy,  X-ray  diffraction pattern, Brunauer e Emmett e Teller surface area analysis and infrared spectroscopy. It is found that the nanocomposites exhibit a high catalytic activity for hydrogen evolution reaction with low overpotentials,high current densities and long-term stability.