In recent years, the layered semiconductor tin selenide (SnSe) has been of great interest in the thermoelectric field because of its remarkable thermoelectric potential. Here, the as-grown Sn 0.98 Se crystal was found to induce a random secondary phase of SnSe 2 in the host SnSe crystal due to similar formation enthalpy between SnSe and SnSe 2 . In addition, we carefully studied the thermal transport properties of as-grown Sn 0.98 Se crystals and intrinsic SnSe crystals. The Umklapp scattering is the prominent scattering and results in a low thermal conductivity of 0.77 W/m/K at room temperature along a direction in the intrinsic stoichiometry SnSe crystal. Because of the optical phonon contribution suppressed by the nanoscopic SnSe 2 intercalations in the as-grown Sn 0.98 Se crystal, the thermal conductivity further decreased to 0.45 W/m/K in nonstoichiometric as-grown Sn 0.98 Se crystals, which is a two-fold reduction and close to that of amorphous compounds. Our study may shed more light on the origin of the extra low thermal conductivity in as-grown Sn 0.98 Se crystals and may provide an efficient way to modulate thermal conductivity by microstructure engineering.

The SnSe crystal is a promising candidate in the field of thermoelectric materials. In order to elucidate basic physics in the SnSe system, here we report the heavily hole doping SnSe single crystals by the flux method (using alkali halide as solvent). Compared to bad-metal behavior of SnSe grown by the Bridgeman method, the flux-grown SnSe crystals show the metallic conductive behavior consistent with the Landau Fermi liquid (resistivity ρ ∼ T2) with temperatures ranging from 2 to 300 K. Combined angle-resolved photoemission spectroscopy and empirical Landau Fermi liquid theory, screening lengths λ of Coulomb electron–electron interaction U of SnSe grown by the flux method are 6.6 Å and 6.1 eV, which are much higher than those of normal metals. Remarkably, the excellent electrical conductivity (870 S/cm) of the SnSe crystal grown by the flux method at room temperature is attributed to the higher hole concentration (∼3.8 × 1019 cm−3) and large mobility (152.2 cm2 V−1 s−1). Meanwhile, these SnSe crystals still have large Seebeck coefficients (∼190 μV/K). Thus, the SnSe crystals grown by the flux method have an ultrahigh power factor [∼31.5 μW/(cm K2)] at room temperature, which is ten times larger than that of SnSe crystals grown by the Bridgeman method and as best as currently reported results. Our work shows a method for growing heavily hole-doped SnSe crystals, which provides a platform for understanding the electrical properties and improving its thermoelectric performance.

The reduction of nitro‐compound to amino‐compound through catalytic transfer hydrogenation over Pd‐based nanostructured composites is an attractive issue. Herein, a series of nanocomposites including Pd nanoparticles with low weight loading anchored on N, Co‐doped carbon framework (Co@NC) was prepared by a facile method. Among these, 1.5 % Pd/Co@NC had the highest catalytic activity towards the reduction of nitrophenols. The enhanced activity may be ascribed to N‐doping, synergistic effect and the interaction between well‐dispersed Pd nanoparticles and N, Co‐doped carbon framework by stabilizing metal nanoparticles with smaller size and good dispersion, improving the adsorption of reactants on the surface of Pd/Co@NC and facilitating electron transfer from NaBH4 to the product. Furthermore, the catalyst maintained regular morphology and activity even after recycling experiments, indicating that it may be used in industrial applications.