A lateral built-in field of the 2D/2D SnS2/SnSe2 in-plane heterostructure with boosted interfacial charge transfer

Abstract

Heterostructure construction is an effective strategy for enhancing the properties of functional materials. However, the problems of lattice mismatch and weak built-in field in the heterointerface usually degrade the interfacial charge transfer efficiency, severely limiting the improvement of sensing properties for gas sensors. To break through this limitation, we attempted to build a lattice-matched SnS₂/SnSe₂ in-plane heterostructure as a NO₂ gas sensor, for which the capability was revealed by DFT calculations. The SnS₂/SnSe₂ in-plane heterostructures with atomically sharp interfaces were synthesized by the topotactic anion-exchange method. The content and spatial arrangement of in situ grown SnSe₂ can be tuned in the heterostructures by adjusting the Se precursor. Ultrahigh response (1165.2%), sensitivity (322.0% ppm⁻¹) and rapid response/recovery (80/78 s) to NO₂ (4 ppm) were realized at room temperature for the optimal SnS₂/SnSe₂ in-plane heterostructure. The response value was 24.7 and 9.5 times higher than that of the common SnS₂/SnSe₂ heterostructures prepared by mechanical mixing and solvothermal deposition, respectively. The response and recovery times were also improved by a factor of 3.5/8.9 and 1.6/4.9, respectively. The superior sensing properties are attributed to the atomic-level sharp in-plane SnS₂/SnSe₂ heterointerface with a lateral built-in field that not only improves NO₂ adsorption but also boosts the interfacial charge transfer along the 2D plane. The ion-exchange growth of the 2D in-plane heterostructure is expected to expand to other 2D nanomaterial systems for applications in sensors, photoelectronics, and catalysts.