First principles study of optoelectronic and photocatalytic performance of novel transition metal dipnictide XP₂ (X = Ti, Zr, Hf) monolayers

Low cost and highly efficient two dimensional materials as photocatalysts are gaining much attention to utilize solar energy for water splitting and produce hydrogen fuel as an alternative to deal with the energy crisis and reduce environmental hazards. First principles calculations are performed to investigate the electronic, optical and photocatalytic properties of novel two dimensional transition metal dipnictide XP₂ (X = Ti, Zr, Hf) monolayers. The studied single layer XP₂ is found to be dynamically and thermally stable. TiP₂, ZrP₂ and HfP₂ systems exhibit semiconducting nature with moderate indirect band gap values of 1.72 eV, 1.43 eV and 2.02 eV, respectively. The solar light absorption is found to be in energy range of 1.65-3.3 eV. All three XP₂ systems (at pH = 7) and the HfP₂ monolayer (at pH = 0) that straddle the redox potentials, are promising candidates for the water splitting reaction. These findings enrich the two dimensional family and provide a platform to design novel devices for emerging optoelectronic and photovoltaic applications.