Coverage Dependence of the Level Alignment for Methanol on TiO${}_2$(110)

Abstract

Electronic level alignment at the interface between an adsorbed molecular layer and a semiconducting substrate determines the activity and efficiency of many photocatalytic materials. We perform $G_0{W}_0$ calculations to determine the coverage dependence of the level alignment for a prototypical photocatalytic interface: 1/2 and 1 monolayer (ML) intact and dissociated CH${}_3$OH on rutile TiO${}_2$(110). We find changes in the wavefunction's spatial distribution, and a consequent renormalization of the quasiparticle energy levels, as a function of CH${}_3$OH coverage and dissociation. Our results suggest that the occupied molecular levels responsible for hole trapping are not those observed in the ultraviolet photoemission spectroscopy (UPS) spectrum. Rather, they are those of isolated CH${}_3$O on the surface. We find the unoccupied molecular levels have either 2D character with weight above the surface at 1 ML coverage, or significant hybridization with the surface at 1/2 ML coverage. These results suggest the resonance observed in the two photon phooemission (2PP) spectrum arises from excitations to unoccupied "Wet electron" levels with 2D character.

8 pages, 5 figures, 1 table

References in corpus (5)

• Renormalization of Molecular Electronic Levels at Metal-Molecule Interfaces
• Quasiparticle and Optical Properties of Rutile and Anatase TiO${}_2$
• Quasiparticle level alignment for photocatalytic interfaces
• Trends in Metal Oxide Stability for Nanorods, Nanotubes, and Surfaces
• Quantitative analysis of valence photoemission spectra and quasiparticle excitations at chromophore-semiconductor interfaces

Cited by in corpus (3)

• Comparing quasiparticle H${}_2$O level alignment on anatase and rutile TiO${}_2$
• Quasiparticle interfacial level alignment of highly hybridized frontier levels: H${}_2$O on TiO${}_2$(110)
• Using surface plasmonics to turn on fullerene's dark excitons