Theoretical study on enhancing the monolayer MoS2 photocatalytic water splitting with alloying and stress
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摘要: 基于密度泛函的第一性能原理计算方法研究了单层MoS2分别与MoSe2、MoTe2、WS2进行合金化, 以及加入2%应力条件下, 对光催化裂解水性能的影响。计算结果表明, 单层MoS2通过与MoSe2、MoTe2、MoWS2进行合金化, 并施加压应力两种手段进行调控, 可使带隙变大的同时, 提高CBM(conduction band minimum)带边位置, 从而提高光催化分解水的效率。通过能带和态密度的计算表明, 合金元素原子形成的不是孤立能级而是能带, 对载流子寿命影响小。Abstract: Based on the density functional theory, the photocatalytic water splitting reaction has been studied over the monolayer MoS2 alloying with MoSe2, MoTe2 and WS2 under stress condition. The calculated results show that the monolayer MoS2 alloyed with MoSe2, MoTe2 and MoWS2 under the compressive stress condition can increase the band gap and improve the position of CBM (conduction band minimum) band edge to enhance the efficiency of photocatalytic water splitting. The calculated energy band and density of states show that the alloy elements form energy band instead of isolated energy level, which has little effect on carrier life.
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Key words:
- single-layer MoS2 /
- strain /
- photocatalytic water splitting /
- band structure
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图 1 MoS2(a)及其合金(Mo9S17Se(b)、Mo9S17Te(c)、Mo8WS18(d))结构示意图
Figure 1 Structure of MoS2 (a), Mo9S17Se(b), Mo9S17Te (c), Mo8WS18(d)
图 2 不施加力(a)、施加拉应力(b)和施加压应力(c)的带边位置图
Figure 2 Calculated band alignments for different conditions (a) original (b) applying stretch strain (c) applying compress strain (the vacuum level is taken as zero reference)
图 3 MoS2及其合金的能带结构示意图
Figure 3 Band structures of ((a), (e)) MoS2, ((b), (f)) Mo9S17Se, ((c), (g)) Mo9S17Te, ((d), (f)) Mo8WS18 ((a), (b), (c), (d) are under zero strain condition; (e), (f), (g), (h) are under 2% compress strain condition)
图 4 三种合金材料在费米能级附近的PDOS谱图
Figure 4 Projected density of states for (a)MoS2, (b)Mo9S17Se, (c)Mo9S17Te, (d)Mo8WS18 with zero strain condition and (e) MoS2, (f) Mo9S17Se, (g) Mo9S17Te, (h) Mo8WS18 with 2% compress strain condition
表 1 优化后晶格常数及组成比例
Table 1 Optimized structure lattice constant
Material and composition Lattice constant /nm Intrinsic MoS2 0.318 Mo8WS18 0.956 Mo9S17Te 0.961 Mo9S17Se 0.958 
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表 2 结构优化后的键长参数
Table 2 Bond length of optimized structure
Material MoS2 Mo8WS18 Mo9S17Te Mo9S17Se Bond length S-MO-S S-W-S S-Mo-Te S-Mo-Se /nm 0.243 0.241 0.272 0.254 0.241 0.241 0.240 0.240 Bond angle
/(°)81.98 82.37 78.15 80.49
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