Thermoelectric, and optoelectronic properties of tetragonal graphene doped with silicon for photocatalytic applications: First-principles calculations

Abstract

In this study, first-principles calculations were employed to investigate the impact of silicon doping on the thermoelectric, optical, and photocatalytic properties of monolayer tetragonal graphene (t-graphene). The findings reveal that silicon doping significantly alters and enhances the bandgap of t-graphene, with the bandgap increasing from 1.71 eV to 3.22 eV as the silicon concentration rises, based on HSE06 calculations. Additionally, the optical properties highlight the potential of these materials for applications in optoelectronics, and photovoltaics. Photocatalytic analysis further reveals that Si-doped t-graphene achieves enhanced photocatalytic efficiency, particularly at doping concentrations of 37.5 % and 50 %. As the silicon concentration increases from 12.5 % to 50 %, there is a notable improvement in the band edge positions, transitioning the material from a photoanode behavior at 12.5 % doping to efficient photocatalytic activity at 50 %. When examining the effect of pH on photocatalytic properties, it was observed that at doping levels between 37.5 % and 50 %, the material can facilitate water splitting into O₂ and H₂. However, with 12.5 % doping, the material retains its photoanode character at various pH levels. Furthermore, transport property analysis indicates that Si-doped t-graphene with a 50 % doping concentration achieves a high figure of merit of 0.99. A higher ZT factor indicates improved energy conversion efficiency, which has important implications for various applications such as photocatalysis, air and water pollution control, and solar energy conversion.