Electrocatalytic performance of MoS2 nanosheets grown on a carbon nanotubes/carbon cloth substrate for the hydrogen evolution reaction

Abstract

Two dimensional (2D) layered molybdenum sulfide (MoS2) exhibit unique advantages as electrocatalyst for the hydrogen evolution reaction (HER). However, the low conductivity of MoS2 itself still limit the overall HER rate. In this work, MoS2 nanosheets grown on a carbon nanotubes (CNTs)/carbon cloth (CC) were used as a cathode electrode for HER under alkaline electrolysis. A MoS2/CNTs/CC were prepared by a hydrothermal method using a precursor solution of sodium molybdate (Na2MoO4·2H2O), thiourea (SC(NH2)2), oxalic acid (C2H2O4·2H2O) and deionized water. The oxalic acid is used as a reducing agent and its concentration plays a significant role in controlling the size and the HER performance of MoS2 nanosheets. The MoS2/CNTs/CC catalyst prepared with the oxalic acid concentration of 5.625 mM shows the optimal HER activity, exhibiting the overpotential of 134 mV at a current density of 10 mA cm-2, Tafel plots of 45.7 mV dec-1, electrochemical double layer capacitance of 123.9 mF cm-2, electrochemical surface area of 3097.5 cm2 and very high durability. The improved HER activity is attributed to the more exposed active sites for the smaller size MoS2 nanosheets and improved conductivity of MoS2 nanosheets by CNTs.