Three-Dimensional Heterostructures of MoS2 Nanosheets on Conducting MoO2 as an Efficient Electrocatalyst To Enhance Hydrogen Evolution Reaction

Molybdenum disulfide (MoS2) is a promising catalyst for hydrogen evolution reaction (HER) because of its unique nature to supply active sites in the reaction. However, the
low density of active sites and their poor electrical conductivity
have limited the performance of MoS2 in HER. In this work, we
synthesized MoS2 nanosheets on three-dimensional (3D) conductive MoO2 via a two-step chemical vapor deposition (CVD) reaction. The 3D MoO2 structure can create structural disorders in MoS2 nanosheets (referred to as 3D MoS2/MoO2), which are
responsible for providing the superior HER activity by exposing
tremendous active sites of terminal disulfur of S2 −2 (in MoS2) as well
as the backbone conductive oxide layer (of MoO2) to facilitate an
interfacial charge transport for the proton reduction. In addition,
the MoS2 nanosheets could protect the inner MoO2 core from the
acidic electrolyte in the HER. The high activity of the as-synthesized 3D MoS2/MoO2 hybrid material in HER is attributed to the small onset overpotential of 142 mV, a largest cathodic current density of 85 mA cm−2, a low Tafel slope of 35.6 mV dec−1, and robust electrochemical durability.