Two-dimensional MX₂Y₄ systems: ultrahigh carrier transport and excellent hydrogen evolution reaction performances

Abstract

Very recently, two-dimensional MoSi2N4 has been synthetized (Science, 2020, 369, 670–674). In this work, we systematically explore the mechanical, electronic, and catalytic properties of the MX2Y4 (M = Cr, Hf,...

Predicted XN (X = C, Si, Ge, and Sn) Monolayers with Ultrahigh Carrier Mobility: Potential Photocatalysts for Water Splitting

“…Besides, the mobility of the electron is about 26 times higher than that of the hole in the same transport direction, and the larger mobility difference between the electron and the hole can further promote the separation in water splitting as a photocatalyst. The same reason goes for SiN and GeN monolayers as photocatalysts, while the GeN demonstrates decent electron mobility of ∼2.5 × 10 3 cm 2 ·V –1 ·s –1 , which is comparable with that of WSi 2 N 4 monolayer (2.2 × 10 3 cm 2 ·V –1 ·s –1 ) . The SiN possesses the highest mobility for the hole of about 628 cm 2 ·V –1 ·s –1 in y -direction, while it is still higher than those of the TMDs, such as MoSSe (193 cm 2 ·V –1 ·s –1 ) and MoS 2 (200 cm 2 ·V –1 ·s –1 ) .…”

“…Obviously, the SnN monolayer possesses the highest carrier mobility of ∼1.55 × 10 4 cm 2 ·V –1 ·s –1 for the electron, indicating potential for high-speed electronic devices. Such ultrahigh carrier mobility is even higher than those of other monolayers like black phosphorus (∼10 4 cm 2 ·V –1 ·s –1 ) and TiSi 2 N 4 (∼1.04 × 10 4 cm 2 ·V –1 ·s –1 ) . Besides, the mobility of the electron is about 26 times higher than that of the hole in the same transport direction, and the larger mobility difference between the electron and the hole can further promote the separation in water splitting as a photocatalyst.…”

“…The most stable HER configurations of the CN, SiN, GeN, and SnN monolayers are obtained by the P2, P2, P1, and P3, respectively, with the free energy of 3.85, 1.12, 0.64, and −0.73 eV, as shown in Figure 6b. The excellent HER performances of the GeN and SnN are more favorable than those of other reported 2D materials, such as MoS 2 (∼2 eV), 67 MoSi 2 N 4 (∼2.33 eV), 17 and graphene (∼1.41 eV). 46 The novel HER ability further illustrates that XN monolayers could be considered as potential photocatalysts for water splitting.…”

“…The same reason goes for SiN and GeN monolayers as photocatalysts, while the GeN demonstrates decent electron mobility of ∼2.5 × 10 3 cm 2 •V −1 •s −1 , which is comparable with that of WSi 2 N 4 monolayer (2.2 × 10 3 cm 2 • V −1 •s −1 ). 17 The SiN possesses the highest mobility for the hole of about 628 cm 2 •V −1 •s −1 in y-direction, while it is still higher than those of the TMDs, such as MoSSe (193 cm 2 •V −1 •s −1 ) 62 and MoS 2 (200 cm 2 •V −1 •s −1 ). 63 Differently, the CN monolayer suggests anisotropic carrier transport properties that the mobility of the electron (or hole) in the x-direction is about 41 (or 3) times that in the y-direction, showing a favorable electron (or hole) transport along the x-direction.…”

“…Such ultrahigh carrier mobility is even higher than those of other monolayers like black phosphorus (∼10 4 cm 2 •V −1 •s −1 ) 61 and TiSi 2 N 4 (∼1.04 × 10 4 cm 2 •V −1 • s −1 ). 17 Besides, the mobility of the electron is about 26 times higher than that of the hole in the same transport direction, and the larger mobility difference between the electron and the hole can further promote the separation in water splitting as a photocatalyst. The same reason goes for SiN and GeN monolayers as photocatalysts, while the GeN demonstrates decent electron mobility of ∼2.5 × 10 3 cm 2 •V −1 •s −1 , which is comparable with that of WSi 2 N 4 monolayer (2.2 × 10 3 cm 2 • V −1 •s −1 ).…”