Function-Oriented Design of Amorphous MoS2 with Abundant Active Sites for High-Efficiency Hydrogen Evolution Reaction

Abstract

Molybdenum disulfide (MoS2) has received great interest as a highly active and cost-effective electrocatalyst for hydrogen evolution reaction (HER). However, a main challenge for developing high-efficiency electrocatalysts is to tailor the factors affecting the HER performance, such as composition, structure, and morphology. Herein, amorphous MoS2 electrodes with different Mo and S contents are successfully synthesized by the chemical bath deposition method using different molar ratios of Mo/S precursors (Mo/S: 4 : 1, 1 : 1 and 1 : 4) at various growth times. Experimental results indicate that the composition and the surface morphology of MoS2 are strongly sensitive to the Mo and S contents, which can create different surface roughness at the interface induced by growth times. The as-prepared MoS2 electrode with a molar ratio of 1 : 4 exhibits superior HER activity in 1 M KOH, only requiring low overpotentials of 220 mV at 20 mA cm−2, which is much lower than those of MoS2 with a molar ratio of 1 : 1 (253 mV), and 4 : 1 (290 mV), respectively. This outstanding electrochemical performance of MoS2 (Mo/S, 1 : 4) with excellent long-term stability can be attributed to its unique sulfur-rich MoS2 nanosheet array structure with exposed abundant active sites, a high electrochemical active surface area (ECSA: 955.50 cm2) and superior roughness factor (RF: 3822).