HRTEM images of the catalysts were obtained on a Tecnai G2 20 Icotinib microscope with a 0.14 nm lattice-fringe resolution and an accelerating voltage of 200 kV. The high-resolution images of the periodic structures were analysed using the Fourier method. Local energy-dispersive X-ray analysis (EDXA) was carried out on an EDXA spectrometer fitted with a Si (Li) detector with a 130 eV resolution. The samples used for HRTEM were prepared on a perforated carbon film mounted on a copper grid, and 10–15 representative micrographs were obtained for each catalyst in high-resolution mode. Typically, the lengths of at least 400 slabs were measured for each catalyst. To measure the extent of WS2 dispersion, the average fraction of W atoms at the WS2 edge surface (D) was calculated, assuming cell body the WS2 slabs were perfect hexagons . WS2 dispersion (D) was statistically evaluated by dividing the total number of W atoms at the edge surface (We), including corner sites (Wc), by the total number of W atoms (WT) using the slab sizes measured in the TEM micrographs:equation(1)D=We+WcWT=∑i=1..t6ni−6∑i=1..t3ni2−3ni+1,where ni is the number of W atoms along one side of the WS2 slab, as determined by its length, and t is the total number of slabs in the TEM micrograph.