Self-Assembled p–n Homojunction in SnS₂ Nanosheets for Enhanced Visible Light-Driven Photocatalysis

Abstract

Defect engineering and hetero-interfacial bending are standard approaches for enhancing carrier separation and increasing visible light absorption in a semiconductor photocatalyst. Here, we demonstrate the evolution of sulfur vacancies (V S ) and the self-assembly of a p−n homojunction through prolonged aqueous washing of SnS 2 nanosheets. The experimental studies have validated increased hydrophilicity, layer thinning, V S generation, and extended photocarrier lifetime in washed SnS 2 nanosheets. Density functional theory has revealed the changes in the local electronic structure of SnS 2 in the presence of structural defects. An electrochemical impedance spectroscopy study has shown that V S actuates the self-assembly of a pseudo-p-type SnS layer over n-type SnS 2 to generate the p−n homojunction. The ptype carrier densities are increased twice as the number of washings is increased from 3 to 10 times. The photocatalytic efficacy of the SnS 2 homojunction is evaluated in the study of the degradation of several water contaminants under white light and monochromatic excitations. The proposed mechanism shows that the built-in electric field at the p−n junction promotes the separation of the photogenerated electrons and holes. Meanwhile, V S traps the electrons and transfers them to the catalytically reactive centers to participate in photocatalysis. Our findings demonstrate that a simple approach that involves prolonged aqueous washing of as-produced SnS 2 promotes the formation of V S and the self-assembly of a p−n homojunction in SnS 2 nanosheets with improved visible light photocatalytic performances.

Bi4O5Br2 Nanoflower and CdWO4 Nanorod Heterojunctions for Photocatalytic Synthesis of Ammonia

“…The PL peak of the 20% BOB/CWO sample is much lower compared to CdWO 4 and Bi 4 O 5 Br 2 . Given that the PL emission arises from electron–hole recombination, the reduced PL signal of the BOB/CWO sample indicates an enhanced efficiency in charge-carrier separation, , consistent with the preceding electrochemical analyses.…”

Self-Assembled p–n Homojunction in SnS2 Nanosheets for Electrocatalytic Hydrogen Evolution: The Role of Sulfur Defects

“…The impact of extended washing on the fractionation and layer thinning of SnS 2 has been reported in our earlier work . The process is described through a scheme, as shown in Figure a.…”

“…(b) XRD of the S3 and S10 nanosheets. The inset shows an enlarged (002) peak of the S3 and S10 nanosheets . (c,d) TEM images of S3 and S10 nanosheets (the inset of d shows the nanosheet size distribution of S10).…”

“…(a) Raman spectra of S3 and S10. High-resolution (b,c) S 2p and (d) Sn 3d XPS spectra of S3 and S10 . (e) Electron paramagnetic resonance plots for S3 and S10.…”

“…Synthesis and washing of the as-synthesized materials were performed with deionized water (Milli-Q IQ 7000, Millipore). A facile and easy hydrothermal technique was adopted to prepare SnS 2 nanosheets . Precursors of Sn and S were mixed in a 1:4 (mmol) ratio with 80 mL of deionized water and stirred well for 30 min.…”