  The potential application of the single-layer MoS2 as photocatalyst was
revealed in this work based on first-principles calculations. It is found that
the pristine single-layer MoS2 is a good candidate for photocatalyst, and its
catalyzing ability can be tuned by the applied mechanical strain. Furthermore,
the p-type doping could improve the catalyzing ability more efficiently: first,
the p-type doping makes the direct transition of electron from valence band
maximum (VBM) to conduction band minimum (CBM) viable; second, it separates the
water splitting reaction sites by having reduction in Mo sites and oxidation in
P dopant sites; third, it improves the efficiency by equalizing the reducing
power {\Delta}1 and oxidizing power {\Delta}2, as well as by enhancing the
light absorption in long wavelength end of the visible light. Thus enables the
single-layer MoS2 to be a efficient visible-light photocatalyst.
