Room-temperature coating of Mn3O4–2D material (graphene and MoS2) nanocomposites for improving oxygen evolution reaction kinetics

Two-dimensional nanomaterials such as graphene nanosheets and molybdenum disulfide nanoflakes were easily hybridized with spinel Mn3O4 in a single deposition process at low temperature by a facile kinetic spray approach under low vacuum conditions using a nano-particle deposition system. The heterostructured Mn3O4–2D hybrid nanocomposites (NCs) were utilized to enhance the reaction kinetics of oxygen evolution. Hybrid NCs of Mn3O4 with MoS2 and graphene showed nanoflakes and nanosheet morphologies, respectively. The synergy improvement in nanocomposites of Mn3O4-graphene nanosheets and Mn3O4−MoS2 nanoflakes was examined by x-ray photoemission spectroscopy and analysis of Raman spectra that results in a decrease in OER overpotential to 289 mV at 10 mA⋅cm−2 for Mn3O4-graphene nanosheets and 295 mV for Mn3O4−MoS2 nanoflakes. The estimated Tafel slope strongly decreased from 88 mV⋅dec−1of pure Mn3O4 nanorods to around 44 mV⋅dec−1 for hybrid NCs. This behavior indicates improved charge transfer kinetics due to the decrease in charge transfer resistance. Furthermore, all fabricated nanostructure electrocatalysts exhibited very good stability for prolonged galvanostatic polarization up to 50 h.