Surface functionalization of penta-siligraphene monolayer for nanoelectronic, optoelectronic and photocatalytic water-splitting: A first-principles study

Herein, we have investigated theoretically using density functional theory the effect of surface functionalization with hydrogen, fluorine and chlorine atoms on electronic and optic properties of the penta-siligraphene monolayer (p-Si2C4). By assessing the stability, we have found that the hydrogenated p-Si2C4 monolayer (p-Si2C4-4H) is energetically (negative formation energy), dynamically (absence of soft modes) and thermally (small drift in the total energy at standard temperature) stable. The electronic-property analysis revealed that the p-Si2C4-4H monolayer is a semiconductor with indirect bandgap varying from 2.06 to 3.41 eV depending on the used functional. Moreover, the p-Si2C4-4H monolayer exhibits a considerable absorption in the ultra-violet (UV) region and a negligible amount of absorption in the visible region. Interestingly, the band edge positions of the p-Si2C4-4H monolayer could perfectly satisfy the redox potentials of photocatalytic water splitting. Furthermore, we have found that bandgap of p-Si2C4-4H monolayer can be tuned using biaxial strain. While, according to HSE06 functional, the bandgap decreases from 3.01 (0%) to 2.38 eV (at 5% biaxial strain) corresponding to a good fitting of band edge with redox potentials and an enhancement in the optical absorption in visible-UV region. This Leads to an improvement the photocatalytic performance of p-Si2C4-4H. Our findings suggest the p-Si2C4-4H monolayer as a promising candidate for applications in new generation of nano- and opto-electronics, especially in UV light shielding (for absorbing the harmful-UV radiations), solar cells (as an anti-reflection layers) and photocatalytic water splitting (for hydrogen and oxygen production).