Discovering Solar Materials Through Materials Modeling

Wieckowski, Hunter; Bryant, Julia; Silvera, Ashli

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Discovering Solar Materials Through Materials Modeling

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MXenes are 2D materials with the formula M(n+1)X(n)T(x)—where M represents an early d-block transition metal, X represents a Carbon or Nitrogen atom, and T represents the surface terminations group—that have the potential for photocatalytic applications. Photocatalysis is the process in which a photocatalyst absorbs light, creating an electron-hole pair which creates an environment for oxidation, as the excited electrons are used to reduce an acceptor and the hole is used for the oxidation of donor molecules. MXenes can be useful in many applications because they are so customizable, as the M layer can be a variety of early transition metals and the termination group can be changed to be F, O, OH, etc. For instance, by changing the termination groups on a MXene, the band gap alignment can be adjusted. In photocatalysis, MXenes are mainly useful for promoting photogenerated charge carrier separation due to their Fermi level which is lower than most known semiconductors and therefore allows electrons to flow from the semiconductor to the MXene. MXenes properties can be simulated using DFT calculations to reduce the need for laboratory testing. In this report, we discuss the role of MXenes in photocatalysis and how density functional theory (DFT) can be used to model MXenes. We then present our methodology for calculating MXene properties—lattice parameter, magnetic moment, density of states, band structure, work function—using VASP and provide an analysis of our results. Finally, based on our calculations, we recommend that Cr3C2F2 may be useful for photocatalysis due to its high density of states and work function higher than that of Si:H, a common semiconductor used in solar panels. V3C2O2 may also be useful, although it does not have an especially high density of states. Sc3C2F2 was the only MXene modeled to exhibit semiconductor properties, so this MXene could also be useful but further analysis and calculation of more properties is recommended.

This report represents the work of one or more WPI undergraduate students submitted to the faculty as evidence of completion of a degree requirement. WPI routinely publishes these reports on its website without editorial or peer review.

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