(264i) MoS2-Pt Deposited on Nitrogen-Doped Carbon Nanotubes As Efficient Electrocatalyst for Hydrogen Evolution Reaction

Renewable energy sources, such as solar and wind, can supply a large amount of electrical energy in a sustainable mode. However, their massive use has been limited by their variability and intermittent nature. Energy storage systems can be an effective solution to ease these disadvantages. Redox flow battery (RFB) systems have been pointed out as an attractive option for energy storage applications that, also, can enable the integration of renewable energy sources with the current electricity grid. A RFB is an electrochemical device that stores electrical energy as soluble redox electro-active species in a liquid electrolyte for longer cycle life, and quick response times. Recently, the hybrid H₂-Br₂RFB system (E_cell=1.09 V) has been subject of different investigations since the redox reactions of Br₂and H₂at the positive and negative electrode, respectively, own fast kinetics and great reversibility. However, the kinetics of the H₂reactions at a Pt/C electrocatalyst is affected by crossover through the membrane of bromide species, reducing the overall performance of the device.

In this research, MoS₂ and MoS₂-Pt nanoparticles were synthesized on nitrogen-doped carbon nanotubes (N-CNT) by a single-step surfactant assisted via. Scanning electron microscopy (SEM) was carried out to study the distribution, particle size and morphology of the nanocomposites. The kinetics and electrocatalytic activity of the nanocomposites were studied by cyclic voltammetry (CV), rotating disk electrode (EDR) and electrochemical impedance spectroscopy (EIS) towards the hydrogen reactions in acidic media with additions of HBr. SEM micrographs showed that MoS₂ or MoS₂-Pt were deposited at the surface of the N-CNT as spherical-particles with 20 nm diameter approximately. Element mapping by SEM confirmed the formation of MoS₂active materials. A decrease in the overpotential for hydrogen evolution reaction was observed when using a one pot synthesis compared to mechanical blend. Finally, MoS₂-Pt @ N-MWCNT exhibited high stability in the presence of HBr as compared with Pt/C electrodes for further use as hydrogen electrode in a H₂-Br₂ RFB.