Compared to standard spectroelectrochemistry, the lock-in amplifier-based EMAS technique achieves an excellent sensitivity allowing to study thin films of 4 nm thickness or less. A more in-depth description of this measurement principle can be found elsewhere. In short, a constant potential, located in the band gap at the open circuit potential (OCP), is applied to the transparent working electrode coated with the sample. This constant potential is modulated with periodic rectangular square pulses, such that a periodic redox potential is applied to the sample given by the amplitude of the square pulse. Simultaneously, the transmission of monochromatic, To facilitate this assignment, it is often useful to compare the EMAS spectrum with the steadystate absorption spectrum. Figure depicts the steady-state absorption spectrum of colloidal 2H-MoS2 nanosheets with a lateral size of 20-25 nm and a thickness of 1-2 monolayers deposited on a fluorine doped tin oxide (FTO) substrate. For better visibility of the main optical transitions, we also plot the second derivative of the data. The A and B excitonic transitions are visible at 658 nm (1.88 eV) and 610 nm (2.03 eV), respectively. The prominent C exciton (or band nesting transition) occurs as a broad signal at 433 nm (2.86 eV) and a shoulder at 388 nm (3.20 eV). Utilizing the empirically found correlation between the number of monolayers per sheet N and A exciton wavelength λA, N = 2.3⋅10 36 ⋅exp(-54888/λA), we anticipate an average layer thickness of 1.36 layers, which is in accordance with the TEM measurements in from the OCP at -0.5 V vs. the Ferrocene/Ferrocenium redox couple (Fc/Fc + ) until a minimum potential of -1.1 V, -1.7 V and -2.9 V vs. Fc/Fc + , respectively. (From here on, all potentials are reported against Fc/Fc + ). It should be noted that the FTO working electrode exhibits a potentialdependent ∆A itself (most notably at λ > 750 nm), but its magnitude is negligible compared to the EMAS signal of thick 2H-MoS2 nanosheet films (cf. Figure ). We find a bleach of the A and B exciton as soon as the potential is increased above the OCP towards more reductive potentials (Fig. ), where the bleach of the B exciton appears more pronounced than that of the A exciton. Further notable features for this reductive scan include the bleach of the C exciton and its shoulder (390 -430 nm), an induced absorption at 700 nm as well as a strong induced absorption between the C and A/B excitonic transitions. The maximum of this last signal shifts towards higher energies with more reductive potentials. Upon increasing the reductive potential Above |-1.2 V|, the formerly clearly separated bleaches of the A/B exciton broaden and dissolve into a single feature (Fig. ). We find that the change in ∆A is non-monotonous, which is why we depict the potential-dependent ∆A for selected wavelengths in Figure . Most notably, the bleach of the A-and B-exciton exhibits two relative maxima at roughly -1.5 V and -2.4 V.