Sulfur vacancy induced high performance for photocatalytic H2 production over 1T@2H phase MoS2 nanolayers

The MoS2 nanostructure has been widely studied as a co-catalyst for photocatalytic H2 production, but itself is seldom studied as a photocatalyst. Herein, we synthesized bicrystalline (1T embedded in 2H phase) MoS2 thin nanolayers with sulfur vacancies by a simple hydrothermal method. The ratio of 1T to 2H and the relative concentration of sulfur vacancies could be adjusted by changing the Mo-precursor (Na2MoO4 and (NH4)2MoS4) and hydrothermal temperature. It was found that MoS2 nanolayers synthesized from (NH4)2MoS4 (i.e., MoS2(NMoS)) tended to form flower-shaped aggregates, while those from Na2MoO4 (i.e., MoS2(NaMo)) overlapped and went across each other to form a mesoporous structure. More interestingly, MoS2(NMoS) had a high relative content of 1T phase and sulfur vacancies than MoS2(NaMo). Thus, MoS2(NMoS) demonstrated a H2 production rate that was two times higher than that of MoS2(NaMo), which most likely resulted from the exposure of more active edge sites, the presence of more sulfur vacancies, the higher number of photo-excited electrons, and enhanced electron separation and transfer in MoS2(NMoS). MoS2(NMoS) also showed promising cycle performance for H2 production (20 cycles with 94% retention efficiency) and superior performance to reported MoS2 nanostructures. The important findings in this work could provide an alternative way to design a unique and efficient MoS2-based photocatalyst.