Interface Engineering of an RGO/MoS₂/Pd 2D Heterostructure for Electrocatalytic Overall Water Splitting in Alkaline Medium

To achieve sustainable production of H₂ at ambient temperature, highly active and stable electrocatalysts are the key to water splitting technology commercialization for hydrogen and oxygen production to replace Pt and IrO₂ catalysts. Herein, a modified interface of palladium (Pd) and reduced graphene oxide (RGO)-supported molybdenum disulfide (MoS₂) prepared by the solvothermal followed by chemical reduction method is established, in which abundant interfaces are formed. The phase structure, composition, chemical coupling, and morphology of the two-dimensional nanostructures are established by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy, respectively. A structural phase transformation in MoS₂ is observed from trigonal (2H) to octahedral (1T) by virtue of Pd addition, which is well established from XRD, Raman, and XPS studies. For oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), the RGO/MoS₂/Pd (RMoS₂Pd) catalyst exhibits extremely low overpotential (245 mV for OER and 86 mV for HER) to achieve benchmark current density, with small values of Tafel slope (42 mV dec^–1 for OER and 35.9 mV dec^–1 for HER) and charge transfer resistance. The quantitative study shows the hydrogen production rate of RMoS₂Pd of 335 μmol h^–1 with excellent stability in alkaline medium, which is superior to MoS₂, RMoS₂, and MoS₂Pd. The improved performance of RMoS₂Pd is attributed to the combined synergetic effect of 1T MoS₂, sulfur vacancy, and conducting RGO sheet, which efficiently accelerate the overall electrochemical water splitting.