Two-dimensional tetrahexagonal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="normal">C</mml:mi><mml:msub><mml:mi>X</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>X</mml:mi></mml:math> = P, As, Sb) semiconductors for photocatalytic water splitting under visible light

In this paper, we introduce a family of two-dimensional group-V carbides with an ordered sequence tetragons and hexagons (th-$\mathrm{C}{X}_{2}$, where $X=\text{P}$, As, Sb). We demonstrate that th-$\mathrm{C}{X}_{2}$ monolayers exhibit robust energetic, dynamical, thermal, mechanical stability. Our calculations show the intrinsic structural anisotropy induces strongly anisotropic mechanical, electronic, optical behavior. These offer ultrahigh ultimate tensile strength, comparable graphene, making them suitable for strain engineering electronic properties. They are semiconductors in nature, th-${\mathrm{CP}}_{2}$, th-${\mathrm{CAs}}_{2}$, th-${\mathrm{CSb}}_{2}$ possess quasidirect, direct, indirect band gaps, respectively. The gaps th-${\mathrm{CP}}_{2}$ th-${\mathrm{CAs}}_{2}$ wide enough to provide photogenerated energy required splitting water. Besides, positions edges alignment water oxidation reduction potentials. For th-${\mathrm{CSb}}_{2}$, however, width gap appropriate edge photocatalytic achieved by engineering. Both indirect-to-direct direct-to-indirect transitions can be induced compounds through high charge carrier mobility, which prolongs average lifetime drift. have good absorption ($\ensuremath{\sim}{10}^{5}$ ${\mathrm{cm}}^{\ensuremath{-}1}$) visible ultraviolet regions light spectrum. $G{W}_{0}+$BSE (Bethe-Salpeter equation) reveal they strong excitonic effects first bright binding is calculated as 0.27, 0.52, 0.22 eV Having all these features one package, among best candidates high-performance splitting.