An Ab Initio Study of Two Dimensional SnX₂ and Janus SnXY (X = S, Se) Nanosheets as Potential Photocatalysts for Water Splitting

Abstract

Discriminating appropriate two-dimensional (2D) photocatalysts for hydrogen generation is among the most prospective schemes to tackle with environmental contaminations. Unfortunately, the inferior capability to harvest solar light together with fast recombination of photoexcited carriers can severely reduce the catalytic ability with consequent limited commercial applications. In this work, a series of single-layer MXY (M = Ge, Sn; X, Y = S, Se, and Te) containing T-and Hphases about photocatalytic capabilities are systematically explored by firstprinciples calculations. First, the T-and H-MXY monolayers possess transformable band gaps of 0−2.37 and 0−1.49 eV, respectively. Astonishingly, the values of T-GeS 2 , T-SnS 2 , T-SnSe 2 , T-SnSSe, and H-SnS 2 monolayers are higher than the threshold of redox potential difference (1.23 eV). Also, importantly, the carrier mobilities of anisotropic T-MXY monolayers can reach ∼1 × 10 4 cm 2 V −1 s −1 , which can rapidly transfer and accelerate the separation of the photoexcited carriers during photocatalytic reactions. Inspired by these significant benefits, the T-MXY monolayers have been built for photocatalytic water-splitting. Significantly, the driving force of photoexcited carriers in T-SnX 2 and Janus T-SnSSe monolayers can greatly promote during the redox reactions. Furthermore, the hydrogen reduction and water oxidation reactions of T-SnX 2 and T-SnXY monolayers can proceed spontaneously under irradiation. In addition, the few-layer and even monolayer T-SnS 2 and T-SnSe 2 have been experimentally synthesized in the literature. The potential photocatalysts of singlelayer T-MXY have the 0.25−0.29 J m −2 cleavage energies, and ab initio molecular dynamics simulations further validate their stability. Our results provide support for 2D group-IV−VI chalcogenides for photocatalytic water splitting.

Two-Dimensional Janus van der Waals Heterojunctions SnX2@SnSSe (X = S, Se) as Promising Solar-Driven Water-Splitting Photocatalysts

“…Table S2 summarizes the related detailed parameters and binding energy of excitons along with the indirect HSE06 band gaps. Moreover, the exciton binding energies of T-SnX 2 @SnSSe vdWHs (0.14–0.34 eV) are smaller than those of the corresponding isolated materials and TMD (0.51–0.62 eV) monolayers . The conclusion can confirm the dissociation of photoexcited carrier pairs during the redox reaction.…”

“…The corresponding freestanding materials based on HSE06 functionals are initially considered, as plotted in Figures S16–S17. Table S1 indicates that the band gaps of MX 2 and Janus MSSe monolayers based on the HSE06 functional are 0.48–2.37 eV for the T phase and 0–1.49 eV for the H phase, which are in good accordance with the previous research. − The band gap of Janus MSSe is between those of MS 2 and MSe 2 regardless of the T or H phase, which is similar to the variation tendency of the lattice parameter. Nevertheless, the band gaps of both-phase MX 2 @MSSe vdWHs are all lower than those of their parent materials regardless of the PBE or HSE06 functionals (Figures and S18–S20), which is common in constructing vdW layered compounds.…”

Strain and Electric Field Engineering of G-ZnO/SnXY (X, Y = S, Se) S-Scheme Heterostructures for Photocatalyst and Electronic Device Applications: A Hybrid DFT Calculation

“…More recently, IV–VI chalcogenides MLs have emerged as a new class of 2D semiconductors that are nontoxic, chemically and experimentally stable, and abundant on earth . It has been reported that 2D SnXY (X, Y = S, Se) layers, including SnS 2 , SnSe 2 , and janus SnSSe, can be successfully synthesized using method like chemical vapor deposition (CVD). − Numerous SnXY-based vdWHs with important applications have been studied.…”

Two-dimensional MSi2N4 (M = Ge, Sn, and Pb) monolayers: promising new materials for optoelectronic applications

“…Following that, a theoretical study has shown that SnS 2 nanosheet can be dynamically stable in both Tand H-phases [23]. Furthermore, a series of group IV dichalcogenide monolayers, MXY (M = Ge, Sn; X, Y = S, Se, and Te) containing T and H phases have been explored using first-principles calculations and proposed for photocatalytic water splitting applications [24]. It has also been reported that the PbS 2 monolayer exhibits an unusual negative Poisson's ratio and suitable band edge alignment, which makes it a promising catalyst for photocatalytic water splitting applications [25].…”