Single-Crystal Atomic-Layered Molybdenum Disulfide Nanobelts with High Surface Activity

Nanostructured molybdenum disulfide (MoS2) has emerged as a promising catalytic alternative to the widely used Pt in the hydrogen evolution reaction from water because it is inexpensive and earth-abundant. The central prerequisite in realizing its potential is to enhance the surface activities by increasing the concentration of metallic edge sites. However, MoS2 thermodynamics favors the presence of a two-dimensional basal plane, and therefore, the one-dimensional edge sites surrounding the basal plane are very limited. Herein, we report the first synthesis of single-crystal MoS2 nanobelts with the top surface fully covered by edge sites. The nanobelt structure comprises parallel stacked atomic layers with the basal plane vertical to the substrate, and these layer edges form the top surface of the nanobelt. The surface is highly active: it optically quenches all of the indirect band gap excitons and chemically leads to a high electrocatalytic hydrogen evolution efficiency (a low onset overpotential of 170 mV for an electrocatalytic current density of 20 mA/cm(2) and a Tafel slope of 70 mV/decade).