Publication

Abstract : The ablation of laser with targets of different materials gives thin films, which can be directed for a variety of applications. The nature of the thin films fabricated by ablation is dependent on the ablation rate, exposure time, oxygen partial pressure, and temperature. The influence of chemical and morphological features of thin films can be fruitfully engaged for various applications. In this work, using the pulsed laser deposition (PLD) method, the 2H-MoS2 target was laser-ablated, forming thin films of 1T-MoS2. A time-dependent study was carried out by keeping the 2H-MoS2 in the target carousal, and the laser was ablated for 5, 15, 30, and 45 min. For 5 and 15 min of laser ablation, the prominent phase was 2H-MoS2, whereas, for 30 and 45 min, 1T-MoS2 was the stable phase. The as-formed MoS2 thin films at 5, 15, 30, and 45 min were studied for the hydrogen evolution reaction (HER) in 0.5 M H2SO4 for the first time, and they showed impressive results with low loading. As 1T-MoS2 (30, 45 min) with both edge and basal planes are active for HER, they showed prominent activities compared to 2H-MoS2 (5, 15 min). The 1T-MoS2 phase prepared at 30 and 45 min showed overpotentials of 152 and 156 mV at 10 mA cm–2 with Tafel slopes of 59 and 89 mV/dec, respectively. This new time-dependent study on MoS2 thin films for HER can be beneficial for making stable 1T-MoS2, which proved quite stable compared to other methods. A minimum deviation in overpotential was observed after PSTAT analysis. The lattice was heavily distorted by the harsh cathodization, and the lattice was expanded due to intercalation and deintercalation of the H+ ion, creating a lattice strain in the sample, which enhanced the activity by keeping the 1T phase stable. From TEM results, a 16% increase in lattice expansion along (11̅1) and an ∼14.5% expansion along (102̅) were observed, as supported by XRD (shift to lower Braggs’ angles). The activity of the film was still stable and it showed that there was no change in the phase throughout cycling; further aging study proved the stability of the 1T phase.