2D Nb4 N5 Nanosheets Synthesized by a Template Method

Improved Photo-Excited Carriers Transportation of WS2 -O-Doped-Graphene Heterostructures for Solar Steam Generation

Two-dimensional (2D) transition metal dichalcogenides and graphene have revealed promising applications in optoelectronic and energy storage and conversion. However, there are rare reports of modifying the light-to-heat transformation via preparing their heterostructures for solar steam generation. In this work, commercial WS₂ and sucrose are utilized as precursors to produce 2D WS₂ -O-doped-graphene heterostructures (WS₂ -O-graphene) for solar water evaporation. The WS₂ -O-graphene evaporators demonstrate excellent average water evaporation rate (2.11 kg m^-2  h^-1 ) and energy efficiency (82.2%), which are 1.3- and 1.2-fold higher than WS₂ and O-doped graphene-based evaporators, respectively. Furthermore, for the real seawater with different pH values (pH 1 and 12) and rhodamine B pollutants, the WS₂ -O-graphene evaporators show great average evaporation rates (≈2.08 and 2.09 kg m^-2  h^-1 , respectively) for producing freshwater with an extremely low-grade of dye residual and nearly neutral pH values. More interestingly, due to the self-storage water ability of WS₂ -O-graphene evaporators, water evaporation can be implemented without the presence of bulk water. As a result, the evaporation rate reaches 3.23 kg m^-2  h^-1 , which is ≈1.5 times higher than the regular solar water evaporation system. This work provides a new approach for preparing 2D transition metal dichalcogenides and graphene heterostructures for efficient solar water evaporation.

2D Higher-Metal Nitride Nanosheets for Solar Steam Generation

Higher-metal (HM) nitrides are a fascinating family of materials being increasingly researched due to their unique physical and chemical properties. However, few focus on investigating their application in a solar steam generation because the controllable and large-scale synthesis of these materials remains a significant challenge. Herein, it is reported that higher-metal molybdenum nitride nanosheets (HM-Mo₅ N₆ ) can be produced at the gram-scale using amine-functionalized MoS₂ as precursor. The first-principles calculation confirms amine-functionalized MoS₂ nanosheet effectively lengthens the bonds of MoS leading to a lower bond binding energy, promoting the formation of MoN bonds and production of HM-Mo₅ N₆ . Using this strategy, other HM nitride nanosheets, such as W₂ N₃ , Ta₃ N₅ , and Nb₄ N₅ , can also be synthesized. Specifically, under one simulated sunlight irradiation (1 kW m^-2 ), the HM-Mo₅ N₆ nanosheets are heated to 80 °C within only ≈24 s (0.4 min), which is around 78 s faster than the MoS₂ samples (102 s/1.7 min). More importantly, HM-Mo₅ N₆ nanosheets exhibit excellent solar evaporation rate (2.48 kg m^-2  h^-1 ) and efficiency (114.6%), which are 1.5 times higher than the solar devices of MoS₂ /MF.