| dc.description.abstract | Molybdenum disulfide (MoS2) has recently emerged as a promising catalyst for the hydrogen evolution reaction (HER) in water splitting that may replace the noble metals such as platinum and rubidium, a cost-effective and highly catalytic material. Two-dimensional MoS2 structures with exposed S-edge have been reported as active electrocatalytic catalyst for hydrogen production. We utilize these two different ways to generate exposed active sites: 1. Prepare dense arrays of MoS2 nanoribbons by combining procedures of micromolding in capillaries (MIMIC) and thermolysis of thiosalts ((NH4)2MoS4) as the printing ink. The obtained MoS2 nanoribbons had a thickness reaching as low as 3.9 nm, a width ranging from 157 to 465 nm, and a length up to 2 cm. MoS2 nanoribbons with an extremely high aspect ratio (length/width) of ?7.4 × 108 were achieved. The MoS2 pattern can be printed on versatile substrates, such as SiO2/Si, sapphire, Au film, FTO/glass, and graphene coated glass. In the hydrogen evolution reaction (HER), the high-density MoS2/MoSx nanostructures has the best performance (overpotential of ?211 mV @10 mA/cm2 and a Tafel slope of 43 mV/dec). 2. Freeze drying to produce three-dimensional structures of graphene oxide (rGO), and we then anneal them at 1000 oC to remove the oxide group, thereby enhancing the conductivity. The reduce graphene oxide has a high surface area, high porosity and low weight, so it could be used as a conductive substrate with attached MoS2 nanoparticles. At four different temperature, we discovered that the crystallinity of MoS2 will affect its performance in the HER (overpotential of 163 mV @10 mA/cm2 and a Tafel slope of 41 mV/dec). In those works, we found the best width of MoS2 nanoribbons and temperature to create large amounts of active sites in MoS2/FTO and MoSx/rGO, which facilitate the electrocatalytic performance for water splitting. In the future, it will be a potential material for fuel cell applications. | en_US |