MoS₂ with Controlled Thickness for Electrocatalytic Hydrogen Evolution

Molybdenum disulfide (MoS₂) has moderate hydrogen adsorption free energy, making it an excellent alternative to replace noble metals as hydrogen evolution reaction (HER) catalysts. The thickness of MoS₂ can affect its energy band structure and interface engineering, which are the avenue way to adjust HER performance. In this work, MoS₂ films with different thicknesses were directly grown on the glassy carbon (GC) substrate by atomic layer deposition (ALD). The thickness of the MoS₂ films can be precisely controlled by regulating the number of ALD cycles. The prepared MoS₂/GC was directly used as the HER catalyst without a binder. The experimental results show that MoS₂ with 200-ALD cycles (the thickness of 14.9 nm) has the best HER performance. Excessive thickness of MoS₂ films not only lead to the aggregation of dense MoS₂ nanosheets, resulting in reduction of active sites, but also lead to the increase of electrical resistance, reducing the electron transfer rate. MoS₂ grown layer by layer on the substrate by ALD technology also significantly improves the bonding force between MoS₂ and the substrate, showing excellent HER stability.