  Highly-efficient water splitting based on solar energy is one of the most
attractive research focuses in the energy field. Searching for more candidate
photocatalysts that can work under visible-light irradiation are highly
demanded. Herein, using first principle calculations based on density
functional theory, we predict that the two dimensional silicon chalcogenides,
i.e. SiX (X=S, Se, Te) monolayers, as semiconductors with 2.43 eV~3.00 eV band
gaps, exhibit favorable band edge positions for photocatalytic water splitting.
The optical adsorption spectra demonstrate that the SiX monolayers have
pronounced optical absorption in the visible light region. Moreover, the band
gaps and band edge positions of silicon chalcogenides monolayers can be tuned
by applying biaxial strain or increasing the number of layers, in order to
better fit the redox potentials of water. The combined novel electronic, high
carrier mobility, and optical properties render the two dimensional SiX a
promising photocatalyst for water splitting.
