PtNi and PtMo nanoparticles as efficient catalysts using TEA-PS.BF4 ionic liquid as electrolyte towards HER

Abstract

Carbon-supported bimetallic nanoparticles, PtNi/C and PtMo/C, were synthesized using the borohydride reduction method and were tested as cathode in the hydrogen evolution reaction (HER) employing acid aqueous solution of 3-triethylammonium-propanesulfonic acid tetrafluoroborate (TEA-PS.BF4) ionic liquid as the electrolyte. For comparison a commercial carbon-supported Pt nanoparticles (Pt/C) has been tested. The morphology, composition and structure of the carbon-supported nanoparticles were characterized by EDX, XRD, and TEM. The results obtained by chronoamperometry, Tafel plots and electrochemical impedance spectroscopy (EIS) exhibited an excellent catalytic effect and the same kinetics mechanism for all carbon-supported nanoparticles in HER studied. Results of Tafel analysis showed that the HER rate determining step is the Volmer–Heyrovsky mechanism. In the temperature range 25–80 °C, the PtNi/C and PtMo/C cathodes presented lower activation energy and higher current density than system using the Pt/C cathode. The PtMo/C cathode improves charge transfer kinetics and hydrogen adsorption, while the PtNi/C cathode facilitates the desorption step. These results demonstrate that the carbon-supported bimetallic nanoparticles PtNi/C and PtMo/C are responsible for increasing the catalytic performances of the HER when TEA-PS.BF4 aqueous solution is employed as electrolyte.