(color online) STEM imaging and spectroscopy analysis of MoS₂ based catalysts at the single atom level. (a) High-resolution STEM-HAADF image of the S-zigzag edge in Co–Mo–S catalyst and the corresponding EELS mapping (b) of Mo (in blue) and Co (in red) and (c) S (in yellow). (d) The L_2,3 edges of a 2S and a 1S atomic columns in (c). (e) Schematic of the Co–Mo–S crystal structure. (g) Combined Mo/Co/Fe mapping from the area framed in black in the STEM-HAADF image (f) and (h) corresponding superimposed ball model.^[22]