Abstract:
It is a challenge to identify suitable low-dimensional materials as photocatalysts for photocatalytic water
splitting applications. We have systematically investigated SiN, SiP, and SiAs homo-bilayers that are efficient
for water splitting applications, and studied five different possible stacking configurations for these homobilayers. Our phonon dispersion curve analysis indicates the dynamical stability of odd stackings for all the
studied bilayers. The electronic band structures of these stable stackings of SiX homo-bilayers were studied
using GGA-PBE and hybrid HSE06 functional. All the studied systems are semiconductors with electronic
bandgaps in the range of 2.488–0.948 eV with the hybrid HSE06 functional. Ultrahigh carrier mobilities of
the order of 106 cm2 V−1 s
−1 have been predicted. SiBi (S-I) indicated the highest carrier mobility of 18.1 ×
106 cm2 V−1 s
−1 for electrons along the x-direction. Most impressively, we found that the band edge
potentials of SiP and SiAs straddle the oxidation and reduction potentials in photocatalytic water splitting. It
was observed that only SiN satisfied the oxidation conditions, whereas SiSb and SiBi satisfied the reduction
conditions in water splitting. An excellent optical absorption was obtained for SiN, SiP, and SiAs homobilayers in the visible region, indicating their potential in photocatalytic water splitting. Further, the
electrocatalytic activity towards OER/ORR was investigated using first-principles calculations. The
thermoelectric figure of merit was explored, and the highest value of 1.02 was obtained for the SiSb
monolayer. Our results indicate that Si-based homo-bilayers display promising potential for visible-lightdriven photocatalytic water splitting and thermoelectric applications.
