Edge termination of MoS2 and CoMoS catalyst particles

The edge termination of MoS2 and CoMoS catalyst particles is studied by den sity functional calculations. We show that for structures without vacancies Mo-terminated edges have the lowest edge energies. Creation of vacancies, which are believed to be active sites in these catalyst systems, leads to s tructures having mainly S-terminated edges. Thus, the results indicate that the shape of the MoS2 and CoMoS structures may be a dynamical function of the reaction conditions. Independent of the type of edge termination, the r esults indicate that triangular-shaped nanocrystals may be expected in orde r to maximize the exposure of the favored edges. This is in contrast to the commonly assumed hexagonal morphology, but triangular-shaped MoS2 structur es have in fact recently been observed in STM studies of model systems [1].