We report herein
investigation on crystallization of amorphous
molybdenum sulfide a-MoS
x
induced by electron and laser beam resulting in formation of crystalline
molybdenum disulfide c-MoS2. This crystallization
occurred in situ during transmission electron microscopic and Raman
analyses of a-MoS
x
material.
It was also found that a-MoS
x
to c-MoS2 phase transformation
was not fully beneficial for H2-evolving catalytic performance. c-MoS2 showed better robustness but significantly
lower catalytic performance. Furthermore, c-MoS2 was less tolerant to oxidation stress, as the one caused
by photogenerated holes within the light harvester, compared with a-MoS
x
catalyst. Thus, a-MoS
x
is a better candidate
for implementation within photocatalysts for overall solar water-splitting
application.
Amorphous molybdenum selenide nanopowder, obtained by refluxing Mo(CO) and Se precursors in dichlorobenzene, shows several structural and electrochemical similarities to the amorphous molybdenum sulfide analogue. The molybdenum selenide displays attractive catalytic properties for the hydrogen evolution reaction in water over a wide range of pH. In a pH 0 solution, it operates with a small onset overpotential of 125 mV and requires an overpotential of 270 mV for generating a catalytic current of 10 mA/cm. Compared with molybdenum sulfide, the selenide analogue is more robust in a basic electrolyte. Therefore, molybdenum selenide is a potential candidate for incorporating within an electrolyzer or a photoelectrochemical cell for water electrolysis in acidic, neutral, or alkaline medium.
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