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CSCD
The incorporation of small guest molecules or ions by bottom-up hydrothermal synthesis has recently emerged as a promising new way to engineer 1T-phase MoS2 with high hydrogen evolution reaction (HER) activity. However, the mechanism of the associated structural evolution remains elusive and controversial, leading to a lack of effective routes to prepare 1T-phase MoS2 with controlled structure and morphology, along with high purity and stability. Herein, urea is chosen as precursor of small molecules or ions to simultaneously engineer the phase (~16.4%, ~69.4%, and ~90.2% of 1T phase) and size (~98.8, ~151.6, and ~251.8 nm for the 90.2% 1T phase) of MoS2 nanosheets, which represent an ideal model system for investigating the structural evolution in these materials, as well as developing a new type of 1T-phase MoS2 arrays. Using reaction intermediate monitoring and theoretical calculations, we show that the oriented growth of 1T-phase MoS2 is controlled by ammonia-assisted assembly, recrystallization, and stabilization processes. A superior HER performance in acidic media is obtained, with an overpotential of only 76 mV required to achieve a stable current density of 10 mA·cm–2 for 15 h. This excellent performance is attributed to the unique array structure, involving well-dispersed, edge-terminated, and high-purity 1T-phase MoS2 nanosheets.
This work has been financially support by the National Natural Science Foundation of China (No. 21676300), the Beijing Natural Science Foundation (No. 2184104), the Fundamental Research Funds for the Central Universities (No. 16CX06007A) and China Postdoctoral Science Foundation (No. 2017M610076).