Oxidation-Sulfidation Approach for Vertically Growing MoS₂ Nanofilms Catalysts on Molybdenum Foils as Efficient HER Catalysts

Molybdenum disulfide (MoS₂) has emerged as a promising electrocatalyst for hydrogen evolution reaction (HER). However, the performance of the catalyst suffers from the scarce active sites and poor electrical conductivity. Here we grow vertical MoS₂ films on Mo foils to achieve highly catalytic active sites and enhanced electrical conductivity for facilitating high efficient HER catalysis. The ultrathin nanofilm with a thickness of around 4 nm on molybdenum foils is grown by a two-step method: (1) the molybdenum oxide (MoO₂) nanofilm is achieved by oxidizing the surface of the Mo foil under a low pressure condition and (2) a MoS₂ nanofilm is obtained by sulfurizing the MoO₂ nanofilm in sulfur vapor at 700 °C within 1 min. Furthermore, the vertically aligned MoS₂ nanofilm on Mo foils exhibit excellent stability in acidic solution and the electrochemical measurements show an onset overpotential of as low as 18 mV and a small Tafel slope of 55 mV/dec. The excellent HER catalysis originates from the synergistic effect of the dense catalytic active sites at the vertical MoS₂ surface and superior electron transport along the Mo foil. This study opens a novel avenue for the development of earth-abundant, low-cost electrocatalysts with high HER activities