Photocatalytic Properties of Anisotropic ${\hat{I}}^2$-PtX${}_2$ (X= S, Se) and Janus ${\hat{I}}^2$-PtSSe monolayers

Abstract

The highly efficient photocatalytic water splitting to produce clean energy requires novel semiconductor materials to achieve high solar-to-hydrogen energy conversion efficiency. Herein, the photocatalytic properties of anisotropic ${\hat{I}}^2$-PtX${}_2$ (X=S, Se) and Janus ${\hat{I}}^2$-PtSSe monolayers are investigated based on density functional theory. Small cleavage energy for \{beta}-PtS2 (0.44 J/m2) and ${\hat{I}}^2$-PtSe${}_2$ (0.40 J/m${}^2$) endorses the possibility of their mechanical exfoliation from respective layered bulk material. The calculated results find \{beta}-PtX2 monolayers to have an appropriate bandgap (~1.8-2.6 eV) enclosing the water redox potential, light absorption coefficients (~104 cm${}^{-1}$), and excitons binding energy (~0.5-0.7 eV), which facilitates excellent visible-light driven photocatalytic performance. Remarkably, an inherent structural anisotropy leads to the anisotropic and high carrier mobility (up to ~5 x 10${}^3$ cm${}^2$ V${}^{-1}$ S${}^{-1}$) leading to fast transport of photogenerated carriers. Notably, the small required external potential to derive hydrogen evolution reaction and oxygen evolution reaction processes with an excellent solar-to-hydrogen energy conversion efficiency of ${\hat{I}}^2$-PtSe${}_2$ (~16%) and ${\hat{I}}^2$-PtSSe (~18%) makes them promising candidates for solar water splitting applications.

18 pages, 5 figures, Physical Chemistry Chemical Physics, 2022