First principles study of optoelectronic and photocatalytic performance of novel transition metal dipnictide XP 2 (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 XP 2 (X = Ti, Zr, Hf) monolayers. The studied single layer XP 2 is found to be dynamically and thermally stable. TiP 2 , ZrP 2 and HfP 2 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 XP 2 systems (at pH = 7) and the HfP 2 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.