Mechanism of interlayer spacing on catalytic properties of MoS2 from ab-initio calculation

The effect of interlayer spacing on the catalytic properties of MoS2 is systematically investigated by the ab-initio calculation. The results show that the expansion of interlayer spacing is beneficial to the catalytic hydrogen evolution when the hydrogen coverage on MoS2 is 25% and 50%. In particular, at 25% hydrogen coverage, the controllable tuning of the catalytic properties of MoS2 can be achieved by orderly tuning the interlayer spacing. When hydrogen coverage is up to 75% and 100%, the negative effect of interlayer spacing on the catalytic hydrogen evolution of MoS2 is negligible. Importantly, the 20% interlayer expansion is a critical state. If the interlayer expansion exceeds 20%, the catalytic properties of MoS2 will be greatly improved, which provides an idea to control the catalytic properties of MoS2 through tuning the interlayer spacing. Finally, the enhanced effect of interlayer expansion on the catalytic properties of MoS2 stems from the fact that the expansion of the interlayer spacing causes the occupancy density of the partially occupied antibonding orbitals near the Fermi level of Mo atoms to increase and move toward the high-energy region, which enhances the electron transfer of Mo.