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

Abstract

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.