A Strategy for Low Thermal Conductivity and Enhanced Thermoelectric Performance in SnSe: Porous SnSe_1–<i>x</i>S_<i>x</i> Nanosheets

A higher figure of merit (<i>ZT</i>) can be achieved for tin selenide (SnSe)-based thermoelectric materials by significantly reducing the thermal conductivity (κ) via three promising strategies: substitution with isoelectric atoms, exfoliation of nanosheets (NSs) from a bulk ingot, and chemical transformation of the material into a porous structure. Specifically, SnSe_1–<i>x</i>S_<i>x</i> NSs are prepared from bulk ingots by hydrothermal Li intercalation and subsequent exfoliation. The substitution of S atoms into SnSe and the fabrication of SnSe_1–<i>x</i>S_<i>x</i> NSs contribute to the scattering of phonons at a number of atomic disorders and nanosized boundaries, leading to effective reduction of the κ value and an improved <i>ZT</i>. The introduction of porosity into the material through the chemical transformation process results in further reduction of κ, which leads to a higher <i>ZT</i>. The fabricated porous SnSe_0.8S_0.2 NS has a maximal <i>ZT</i> value of 0.12 at 310 K, which is significantly higher than that of pristine SnSe