Patterning edge-like defects and tuning defective areas on the basal plane of ultra-large MoS₂ monolayers toward the hydrogen evolution reaction

Abstract

Supported and free-standing MoS2 monolayers were patterned using a focused ion beam to tune their electrocatalytic activity toward H2 production. Defects can either be confined near the etched interfaces or spread depending on the applied dose.

Strain and defect-engineering on the basal plane of ultra-large MoS2 monolayers attached onto stretchable gold electrodes

“…The ultra-large MoS 2 monolayers are prepared using a simple and fast electrochemical thinning method recently reported. 43,44 This method is being reported for the first time on corrugated gold films. In brief, we transfer bulk flakes onto gold electrodes using sucrose.…”

“…One of the most used techniques to characterize MoS 2 is Raman spectroscopy. By obtaining Raman spectra one can determine phase change, 61 presence of defects, 44,62 and number of layers. 63 Fig.…”

“…After releasing the electrodes from the stretching condition, bulk MoS 2 crystals (SPI supplies, PA, USA) were mechanically exfoliated using an adhesive tape (Nitto) and transferred onto the stretchable electrodes using a melted sucrose method, as previously described. 43,44 In short, sucrose, sourced from Synth (SP, Brazil), was melted at 250 °C and added dropwise onto the tape hosting pre-exfoliated bulk MoS 2 flakes. Following the solidification of sucrose, the resultant solid piece was carefully detached, placed on the gold substrate, and subjected to washing with heated (100 °C) de-ionized water.…”

“…Initially, chronoamperometry was conducted by setting the potential at 1.5 V vs. Ag/AgCl for 300 s. Subsequently, 10 cyclic voltammetric curves were obtained from −0.1 to +0.5 V at a scan rate of 10 mV s −1 . 43,44 Following the electrochemical thinning process, the stretchable electrodes were either preserved (corrugated samples) or subjected to stretching to induce edge-like defects formation (stretched samples) before proceeding to HER measurements. To isolate the initial basal plane of the MoS 2 monolayers, an insulating resin was employed.…”

“…The electrodes can be stretched up to 20% with minimal impact on their electrical properties, enabling the preparation of MoS 2 monolayers using a fast electrochemical thinning method. 43,44 By applying uniaxial strain on the electrodes, we introduce both strain and edge-like defects on MoS 2 . The presence of strain was confirmed by Raman spectroscopy, atomic force microscopy (AFM), and photoluminescence (PL) experiments, as reported.…”