Correlating Induced Defects in 2D MoS₂ with Raman Spectroscopy to its Electrocatalytic Performance

The excellent performance of two-dimensional materials such as MoS₂ and WS₂ for electrocatalytic reduction reactions such as the hydrogen evolution reaction (HER) has driven the development of diverse synthetic protocols for 2D electrocatalysts. The bulk structure of materials synthesized by these diverse approaches are often similar, but fine structural details such as the degree of lattice strain or the concentration and identity of structural defects often remain unclear. Such understanding is critically important in understanding the differences between synthetic protocols because strain and defects are known to alter electrochemical properties of 2D materials. Raman spectroscopy is highly sensitive to defects in solid-state materials, but 2D materials exhibit a limited number of peaks in Raman spectra and each type of strain or defect is known to alter each feature in a unique way. Our research attempts to quantify the effect of individual defect types on Raman spectroscopic features by combining systematically varied synthetic protocols with a correlation based analysis. This talk will focus on a series of MoS₂ samples that were post-synthetically modified by swift heavy ion irradiation to introduce pores within individual 2D sheets of the MoS₂. Characterization by techniques such as photoluminescence microscopy, electrochemical measurements, and electron microscopy reveal the influence that these defects have on the structure and properties of the series. Subsequent correlational analysis then links the structural of behavioral parameters to quantitative features in the Raman spectra – namely the width, location and intensity of individual peaks. The overarching goal is to establish sufficient correlational maps that a single Raman spectrum can be used as a map for confident defect analysis. Such capabilities will provide the community with a low-cost and user-friendly analysis tool increases the compatibility of the diverse and varied studies being published – a feature that will greatly expedite the development of 2D materials as electrocatalysts.