Inspired by the photocatalytic water splitting process to produce H2, several research works are aim at finding new heterogeneous photocatalysts active in CO2 reduction. To tackle this challenge, layered transition metal dichalcogenides like MoS2 have attracted much attention for their optoelectronic properties, and their tunable nano-structures. However, bulk MoS2 has a too small bandgap (~1.2 eV) to be used efficiently in CO2 photoreduction. To overcome this, MoS2 can be used either as a cocatalyst or in a Z-scheme architecture which combines MoS2 monolayer with another larger bandgap semiconductor, such as TiO2, known for its photocatalysis activity. Our work explores the evolution of the band gap and conduction band (CB)/valence band (VB) positions by using periodic DFT calculations for various types of 2D-MoS2/TiO2-anatase heterojunctions. Two surface orientations of TiO2 particles, (101) and (001), are considered with two interaction types with MoS2: van der Waals or chemical epitaxy (Figure1). CB/VB band positions are computed as a function of the interface’s compositions and structures. We find that these modifications in the heterostructure lead to important changes in the electronic structure which impact the both photon absorption properties and the charge carriers dynamics suspected to influence in turn the photocatalytic activity. Since the behavior of MoS2 as a cocatalyst cannot be neglected, we are studying the CO2 reduction mechanism on MoS2 edges by using the grand canonical DFT approach that is able to simulate the impact of the polarization of the photoelectrodes on the successive adsorption and reaction steps. Two MoS2 edges are considered with various sulfidation, hydration and hydrogenation states where we analyze the possible activation of the CO2 molecule (Figure 2).

DFT investigations of the MoS2 properties as photocatalyst for CO2 reduction

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.