Pentagonal PdTe2 Monolayer for Sustainable Solar-driven Hydrogen Production

Abstract

This investigation demonstrates that the pentagonal PdTe${}_2$ (penta-PdTe${}_2$) monolayer is a highly tunable two-dimensional (2D) photocatalyst, characterized by a bandgap of 1.87~eV and high hole mobility. Using density functional theory (DFT) calculations with the HSE06 functional, we show that tensile strain engineering, particularly at $+2$ and $+3$, is essential for enabling spontaneous water splitting. At these strain values, the valence-band maximum (VBM) and conduction-band maximum (CBM) straddle the water redox potentials (${\mathrm{H}}^{+}/{\mathrm{H}}_2$ and ${\mathrm{O}}_2/{\mathrm{H}}_2\mathrm{O}$) under both acidic ($\mathrm{pH}=0$) and neutral ($\mathrm{pH}=7$) conditions. The monolayer's low hole effective mass facilitates rapid charge extraction, mitigating electron--hole recombination and promoting the oxygen evolution reaction (OER) more effectively than many hexagonal and pentagonal counterparts. The Gibbs free energy ($\hat{I}”G$) pathways indicate that the overpotentials for the hydrogen evolution reaction (HER) and OER are highly sensitive to mechanical deformation, specifically biaxial strain. In particular, a tensile strain of $+3$ yields an optimized balance of overpotentials, with $\hat{I}{\cdot }_{\mathrm{HER}}=0.70\mathrm{V}$ at $\mathrm{pH}=0$ and $\hat{I}{\cdot }_{\mathrm{OER}}=0.72\mathrm{V}$ at $\mathrm{pH}=7$. Finally, integrating optical absorption with thermodynamic driving forces results in a solar-to-hydrogen (STH) efficiency of $20.40$ at $\mathrm{pH}=7$. This performance exceeds that of several previously reported two-dimensional catalysts, positioning penta-PdTe${}_2$ as a superior candidate for sustainable, solar-driven hydrogen production.

11 pages, 7 Figures