MoS(2) with Controlled Thickness for Electrocatalytic Hydrogen Evolution

Molybdenum disulfide (MoS(2)) has moderate hydrogen adsorption free energy, making it an excellent alternative to replace noble metals as hydrogen evolution reaction (HER) catalysts. The thickness of MoS(2) can affect its energy band structure and interface engineering, which are the avenue way to adjust HER performance. In this work, MoS(2) films with different thicknesses were directly grown on the glassy carbon (GC) substrate by atomic layer deposition (ALD). The thickness of the MoS(2) films can be precisely controlled by regulating the number of ALD cycles. The prepared MoS(2)/GC was directly used as the HER catalyst without a binder. The experimental results show that MoS(2) with 200-ALD cycles (the thickness of 14.9 nm) has the best HER performance. Excessive thickness of MoS(2) films not only lead to the aggregation of dense MoS(2) nanosheets, resulting in reduction of active sites, but also lead to the increase of electrical resistance, reducing the electron transfer rate. MoS(2) grown layer by layer on the substrate by ALD technology also significantly improves the bonding force between MoS(2) and the substrate, showing excellent HER stability.