Enhancement in ORR Performance by Compositing Ni-Decorated MoS2 with rGO for Alkaline Fuel Cells

Abstract

Due to its layered structure and appropriate electronic configuration, two-dimensional MoS₂ has been considered a reliable and inexpensive electrocatalyst and electrode material for the oxygen reduction reaction (ORR). Additionally, the MoS₂ and reduced graphene oxide (rGO) structure can act as a good host for other nano-catalysts. However, the catalytic activity of pristine MoS₂ is not as effective as the industrial targeted values. In this work, nickel-MoS₂ (Ni/MoS₂) and Ni/MoS₂-rGO composites are synthesized and evaluated as catalysts for ORR at the cathode. Electrochemical studies using a rotating disk electrode system confirmed that the as-synthesized catalyst exhibits good electrocatalytic activity to ORR in alkaline media (0.1 M KOH) and followed the desirable 4-electron transfer process. Ni/MoS₂-rGO composite displays a current density of − 11.1 mA/cm² and half-wave and onset potentials of 0.74 V and 0.87 V, respectively, at 2400 rpm, whereas the bare MoS₂ shows the values of limiting current density, half-wave potential, and onset potential of − 5.8 mA/cm², 0.61 V, and 0.79 V, respectively. Numerous highly active Mo sites, high conductivity, and high specific surface area in MoS₂-rGO make it a novel catalyst material for ORR. Ni further enhances conductivity and is involved in electrochemical reactions. The onset potential slightly shifts towards the lower value after the potential cycling, whereas the limiting current density decreases by ≈9.0% for Ni/MoS₂-rGO, which shows its good stability in alkaline media. Therefore, Ni/MoS₂-rGO composite can be a good candidate for electrode catalyst material for alkaline fuel cells.

Graphical Abstract