Numerical Simulation and Evaluation of Y\(_2\)S\(_3\) and Y\(_2\)TeS\(_2\) on Structural, Stability, and Electronic Properties for Photocatalytic Water Splitting Applications

We attempt to establish a computational insight into the structural, mechanical, dynamic, electronic, and photocatalytic properties of orthorhombic phase Yttrium sulphide Y₂S₃ and Y₂TeS₃ Janus compounds by density functional calculations. The Janus Y₂TeS₃ is a hypothetical compound with all properties computed forthe first time. Computed lattice parameters for Y₂S₃ are in reasonable agreement with available experimental data. Mechanical properties are investigated by calculating the elastic constant to check for Born stability criteria. A finite displacement vibrational frequency study confirmed that Y₂S₃ and Y₂TeS₃ are stable; negative phonon frequencies were checked. Computed PBEsol and MBJ band structures found that Y₂S₃ is a direct band gap semiconductor, while Y₂TeS₃
is an indirect band gap semiconductor. Band gaps estimated from the HSE06 hybrid functional are 2.75 eV and 2.70 eV for Y2S2 and Y₂TeS₃ respectively, suggesting that they are semiconductor materials with wide band gaps that can absorb light in the ultraviolet region. Mullikan’s electronegativity screen technique, used to calculate valence band maximum VBM and conduction band minimum CBM potentials, predicted that Y2S3 and Y₂TeS₃ have suitable conduction band minimum potential of -1.05 V and -1.30 V and valence band maximum of 1.70 V and 1.40 V, respectively, versus normal hydrogen electrode (NHE) at PH = 0 to trigger the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) simultaneously.