Maximyzing the Potential of Layered Compounds for Hydrogen Production

Layered transition metal dichalcogenides (TMDs) gained much attention in recent years. Layer edges were identified as the catalytic sites, making edge oriented morphologies a desired design. In addition, first principle calculations showed that doping and alloying of TMDs can be used to modify their electronic properties. To date, TMD alloying is primeraly performed at high temperature, solid state reactions, such as chemical vapor deposition (CVD) or chemical vapor transport (CVT) which limit morphology and composition control. We used low temperature, controllable colloidal synthesis to produce nanoflower alloyed TMDs. Specifically Mo(S_xSe_1-x)₂ nanoflowers with edge oriented nanostructures. A range of alloy compositions were prepared. The Materials were analyzed using TEM, XRD, UV-Vis, ICP-MS spectroscopy and electron tomography. We found that the produced nanoflowers were molybdenum rich, in agreement with previous reports. The composition closely follows the feed ratio enabling the production of precisely controlled compositions. XRD and UV-Vis spectra results suggests the formation of a homogeneous solid solution rather than two separate phases of MoS₂ and MoSe₂. Tunable bandgap was achieved as a function of alloying degree, as measured by UV-Vis. Time series analysis results support a growth mechanism of fast-precipitating amorphous material, followed by crystallization of a few layers of small sheets, which curl and tangle around themselves. We have demonstrated the synthesis of improved edge oriented alloys using simple colloidal technique. By controlling the alloying degrees, the electronic properties of the TMDs can be optimized for a variety of applications such as photo catalysis, optoelectronics, transistors and many others.