Quantifying Interfacial Energetics of 2D Semiconductor Electrodes Using in situ Spectroelectrochemistry and Many-Body Theory

2D transition metal dichalcogenides (TMDs) (MX 2 ; M = Mo, W; X = S, Se) have unique electronic properties that may lead to the next generation of photo-electrocatalysis. The fundamental problem is that the interfacial energetics of TMDs are poorly understood. It is essential that we quantify the behavior of the energy bands in monolayer TMDs to understand their electronic properties. In this work, we develop an in-situ absorbance spectroscopy approach to quantify interfacial energetics of 2D semiconductor/electrolyte interfaces using a minimal many-body model to calculate the carrier concentration ( n ). Our results show that band edge movement in monolayer MoS 2 is significant (0.2-0.5 eV) over a narrow range of applied potentials (0.2-0.3 V). Such large band edge shifts could change k ET by a factor of 10-100, which has important consequences for practical solar energy conversion applications. In addition, our results show that we can modulate n of TMDs by introducing a redox couple in the electrolyte solution. I will discuss how these findings relate to solar energy conversion in photoelectrochemical cells.