“…8 Transition metal chalcogenides, such as MoS 2,9,10 CoP, 11 CoSe 2 , 12 and WS 2 , 13 show good catalytic performance, hence attracting much attention to be used as electrocatalysts for HER. However the catalytically active sites located at the edges site in either metallic or semiconducting transition metal suldes, 14 and in the trithio-or triseleno-phosphate compounds as well, 15 20 have also been evaluated as electrocatalysts for HER. Besides, many other approaches, such as decreasing the size, 8 introducing defects, 21,22 and controlling the phase transition [23][24][25] in MoS 2 , have been proposed to increase the catalytically active sites.…”