(82h) S-Modified Mxenes for Hydrogen Evolution Reaction - a Computational Approach
AIChE Annual Meeting
Tuesday, November 17, 2020 - 9:00am to 9:15am
Discovering materials with cheap and abundant elements, tunable properties, and platinum like chemical activity is crucial in advancing the hydrogen economy of production and storageÂÂÂÂÂÂÂÂ. In this study, we use density functional theory to capture the compositional and structural effects of sulfur modifications to twelve distinct Mo- and Ti-based 2D MXene materials on their stability and activity for catalyzing the hydrogen evolution reaction (HER). The explored S-modifications include (i) S substitution of the O functional group/termination, (ii) S substitution of the carbon of the MXene , (iii) S intercalation into the MXene material, (iv) S adatom onto the MXene basal plane, and (v) MXene â MoS2 heterostructure. These computational models are geometric, stoichiometric, and structural in nature and allow for comparison with experimentally synthesized S-treated MXenes, which are tested for HER. We perform structural optimization to evaluate changes in lattice parameters due to the presence of S in the MXenes systems. We identify a direct relationship between hydrogen adsorption energy and the S atomic composition of the MXenes. Furthermore, we demonstrate that S substitution into the C position of the MXene results in a decrease in the theoretical HER overpotential in Mo-based MXenes while the S substitution into the O position results in a decrease in the overpotential in Ti-based MXenes. We find that the Mo-based S-modified MXenes span a larger range in the calculated theoretical HER overpotential as compared to the Ti-based MXenes. Based on our screening study, S modified Ti-based MXenes Ti3C2, Ti2MoC2, Ti4C3, Ti2Mo2C3 and TiMoTiMoC3 have theoretical overpotentials lower than 0.03 V. Almost all O-term MXenes in this study are predicted to be improved by some form of S treatment. This screening report opens the field to consideration of using S in the design of novel 2D materials to promote a clean hydrogen economy.