Abstract We theoretically propose unknown monolayer C3N2 and janus monolayer C3PN with high stability based on first-principles calculations. By using HSE06 functional, we get that monolayer C3N2 exhibits a wide indirect band gap 3.15 eV, mediocre carrier mobility and appropriate band edge positions for photocatalytic water splitting. Additionally, the band structure, optical absorption and STH efficiency of monolayer C3N2 can be effectively tuned by strain effect. Most remarkably, designed on the basis of monolayer C3N2 structure, janus monolayer C3PN with a wide indirect band gap 2.58 eV exhibits better performance on photocatalytic water splitting than that of monolayer C3N2 reflecting on owning more obvious separation of photo-generated carriers caused by intrinsic electric field, extraordinary hole mobility, higher STH efficiency and stronger absorption coefficient in visible-light region. Our results not only provide two types of 2D metal-free semiconductors for photocatalytic water splitting but also pave the way for improving their abilities through forming janus structures.

中文翻译：

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用于无金属光催化水分解的宽带隙二维 C3XN（X = N 和 P）

摘要 我们基于第一性原理计算，在理论上提出了具有高稳定性的未知单层C3N2和janus单层C3PN。通过使用 HSE06 泛函，我们得到单层 C3N2 表现出宽的间接带隙 3.15 eV、中等的载流子迁移率和适合光催化水分解的带边位置。此外，单层 C3N2 的能带结构、光吸收和 STH 效率可以通过应变效应进行有效调节。最值得注意的是，在单层C3N2结构的基础上设计的，具有2.58 eV宽间接带隙的janus单层C3PN比单层C3N2表现出更好的光催化分解水性能，这反映了具有更明显的由本征电引起的光生载流子分离场，非凡的空穴迁移率，在可见光区具有更高的 STH 效率和更强的吸收系数。我们的研究结果不仅为光催化水分解提供了两种类型的二维无金属半导体，而且还为通过形成 janus 结构提高其能力铺平了道路。