Two Dimensional Janus Ga₂SX₂ (X = O, S, Se, and Te) Monolayers as Efficient Piezo- and/or Photocatalyst for Green Hydrogen Generation

Developing innovative and environmentally friendly hydrogen generation technologies are pivotal for transition to a carbon-neutral future. In this regard, the integration of photocatalytic and piezoelectric properties of semiconductor catalyst have proved beneficial. As polar nature of piezoelectric materials provides a drive force to photo-generated charge carriers thus enhancing their separation and reducing recombination. Additionally, piezoelectric materials generate a potential under oscillatory strain, commonly known as piezo-potential, can alone initiate the water redox reaction. Therefore, in this study we explore the potential of piezoelectric Janus Ga₂SX₂ (X=O, S, Se, Te) monolayers as efficient piezo- and/or photocatalyst, leveraging density functional theory (DFT) simulations. Our investigation encompasses a comprehensive examination of the structural, electronic, optical, mechanical and piezoelectric properties. Except Ga₂SO₂ all monolayers exhibit semiconducting behaviour, featuring indirect band gaps within the range of 1 eV to 2.7 eV. The band edges are favourable to straddle the photocatalytic water redox reaction under the solar illumination. Moreover, the generated piezo-potential exceeds 3 V which originate from superior piezoelectric and mechanical properties demonstrating the piezo-catalytic water splitting ability. In summary, these findings open new avenues for the development of piezo- and photocatalytic technologies for clean and sustainable hydrogen production.