Strain ng of 2D-C3N5 Monolayer and Its Application in Overall Water-Splitting: a Hybrid Density Functional Study

The recent experimental synthesis of 2D graphiticC3N5has attracted a lot of interest in its electronic and opticalproperties and its comparison with other graphitic C3N4and C3N3.To this end, we performed density functional theory calculationsusing the accurate HSE06 functional and estimated thecorresponding electronic properties. From a comparative studyof the band structures of C3N3,C3N4, and C3N5, we found that theelectronic band gap decreases in the order 3.24 eV (C3N3) > 2.81eV (C3N4) > 2.19 eV (C3N5) with an increase in the number ofnitrogen atoms in the unit cell of these graphitic carbon nitrides.Further, the strain dependency of the band structure of 2D g-C3N5under uniaxial and biaxial strains is performed using the sameHSE-06 functional. We found a systematic decrease of band gap asstrain increases. Out of the two types of strains, the biaxial strain has been found to be more efficient in modulating the band gap.The effect of strain on the structure is also explored by analyzing the bond lengths and bond angles as well as the charge densityplots. Furthermore, we found that at a biaxial strain of 20%, an interesting structural rearrangement occurs in 2D g-C3N5, whichresults in afinite magnetic moment arising from the loss of spin-degeneracy of electronic levels. Finally, by studying the evolution ofband gap, band alignments, and optical absorption as a function of strain, we are able to predict that C3N5with biaxial strain in therange of 12-14% can be a promising photocatalyst in overall water-splitting with excellent optical absorption in the visible lightspectrum

Automated summary

The recent experimental synthesis of 2D graphitic C3N5 has attracted interest in its electronic and optical properties, compared with other graphitic C3N4 and C3N3 materials. Density functional theory calculations and strain dependence studies have shown that increasing the number of nitrogen atoms reduces the electronic band gap, and biaxial strain is more effective in modulating the band gap. Furthermore, structural rearrangement occurs at a 20% biaxial strain, resulting in a finite magnetic moment in 2D g-C3N5.