Carbon monoxide-sensing of SnS nanoflakes induced by the electron-trapped polaron upon the substituted-lithium

Abstract

Two-dimensional (2D) SnS with wrinkled lattice and strong oxidation resistance exhibits malleable talents and great potential for gas-sensing applications. But it suffers the inherent disadvantage of low sensitivity towards weakly polarized gases like CO. Herein, inspired by the unique atomic real polarization and orbital penetration of lithium, a distinct polarized configuration of 2D Li-substituted SnS is proposed for achieving a moderate CO adsorption-desorption dynamics at room temperature. The 2D nanoflakes of Li-SnS, synthesized via one-step solvothermal method, reveal highly sensitive and selective performances towards trace CO as low as 2 ppm at RT. Conducting with first-principles calculations, the substitutional doping of Li in SnS crystal is unveiled as the knob to modulate the electronic state of SnS. The enhanced electron-deficiency states and the local vibration modes of Li atoms, urge the coupling of electrons and longitudinal-optical phonons to form a polaron on each Li site. These polarons serve as efficient electron traps, and synergize with anharmonic local vibrations of Li atoms to form energy state fluctuation, promoting CO adsorption-desorption dynamics and carrier transport for the SnS system. This work provides novel perspectives for understanding the structure-electrical configurations of 2D materials and the microscopic mechanism of gas adsorption.