Prediction of quaternary SnGeS₂As₄ monolayer as a promising photocatalyst for water splitting: a DFT study

Abstract The SnGeS 2 As 4 monolayer was studied by first-principles calculations to estimate its potential for use as a photocatalyst in the water splitting process. The stability of this structure is confirmed based on the analysis of its phonon dispersion and AIDM simulations. The electronic features including density of states (DOS), band structure, and Bader charge were calculated. These data show the role of each constituent element in the formation of covalent <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>π</mml:mi> <mml:mo>−</mml:mo> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>σ</mml:mi> <mml:mo>−</mml:mo> </mml:mrow> </mml:math> bonds, which play an important role in stabilizing the buckled honeycomb structure. In addition, the DOS and band structure also provide information regarding the high light absorption rate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>α</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>ω</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> of 10 5 –10 6 cm −1 . The positions of valence band maximum and conduction band minimum are suitable for generation of hydrogen and oxygen gases. The SnGeS 2 As 4 monolayer also has an optimal work function of 5.16 eV for the water splitting process and a rather high solar-to-hydrogen efficiency <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>η</mml:mi> <mml:mrow> <mml:mi>STH</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>′</mml:mi> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> = 13.11%. It is worth noting that SnGeS 2 As 4 monolayers with strains ranging from −2% to 6% are still capable of triggering redox reactions in the water splitting process. Moreover, the tensile strains slightly increase the light absorption rates. Such characteristics not only make the SnGeS 2 As 4 monolayer a suitable photocatalyst for water splitting but also ensures its performance in a wider range of applications.