Polyoxometalate-decorated graphene nanosheets and carbon nanotubes, powerful electrocatalysts for hydrogen evolution reaction

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-NiO39]−@PDDA-CNT/GCE and [PW11Pt-NiO39]-@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-NiO39]−@PDDA-rGO and [PW11Pt-NiO39]−@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-Emmett-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.