Ag-Nanoinclusion-Induced Enhanced Thermoelectric Properties of Ag₂S

Abstract

The effects of Ag nanoinclusions on thermoelectric properties of Ag 2 S semiconducting nanostructures, synthesized by a novel one-pot facile polyol method, have been investigated. The resulting products are characterized by powder XRD, EDAX, XPS, and UV−vis techniques. FESEM images reveal the formation of disc-shaped Ag 2 S nanoparticles with an average thickness of 52 nm and diameters ranging from 50 nm to a few hundreds of nm. All samples show a systematic reduction in electrical resistivity with increasing Ag content in the composites. The Seebeck coefficient (α) values for the Ag nanoparticle-incorporated Ag 2 S nanocomposites are notably high near 300 K because of the low-energy charge-carrier filtering effect, which is due to preferential scattering of low-energy electrons at the barrier potentials set up at metal−semiconductor interfaces. The theoretical fitting of α data reveals a systematic shift of the Fermi level toward the conduction band edge with increasing Ag content in the composites. A significantly improved thermoelectric power factor at 325 K is observed for a wide range of Ag nanoinclusions with the highest ZT of 0.0029 at 325 K in the Ag 2 S−Ag nanocomposite with 20.1% Ag.

Photocatalytic Reduction of Aromatic Nitro Compounds with Ag/AgxS Composites under Visible Light Irradiation

“…If S 0 presented on the catalyst, it would react with Na 2 S in aqueous reaction solution to form Na 2 S 2 and leave from the surface of the catalyst during the reaction. For the Ag 3d, a Lorentzian function line shape with a spin–orbit splitting fixed to 6.00 eV and a doublet intensity ratio was fixed to 3:2, the peak at the binding energy of 367.5 and 373.5 eV was assigned to Ag 3d 5/2 and Ag 3d 3/2 of Ag + , and that of 368.2 and 374.2 eV was assigned to Ag 3d 5/2 and Ag 3d 3/2 of Ag 0 (Figure b), respectively. − With an increasing l -cys/Ag + molar ratio from 0.5 to 1, the proportion of the S 2 2– and S n 2– species increased (Table , entries 1–3). While these values decreased when the ratio increased from 1 to 8 (entries 3–5).…”

Current State‐of‐the‐Art in the Interface/Surface Modification of Thermoelectric Materials

“…Apart from non‐magnetic and noble metals (such as Pt, [ 56 ] Ag, [ 93 ] and Au [ 77 ] ), the introduction of magnetic metallic nanoparticles (Co/Ni/Fe) with different magnetic states than that of the TE matrix can significantly improve its thermoelectric performance. [ 94 ] It should be noted that the process of magnetic second‐phase dispersion in TE matrices must be separated from the one of doping effect, since due to the extremely low solubility of most magnetic ions in TE materials, the improvement in terms of thermoelectric performance after doping is insignificant.…”

“…It should be noted, however, that certain metal nanoparticles may react with the matrix or generate additional charge carriers, resulting in the increase of the electrical thermal conductivity due to electrical contribution, a phenomenon which has been observed in several systems. [ 67,75,93,104 ]…”

Bottom-Up Engineering Strategies for High-Performance Thermoelectric Materials

“…Apart from the highly conductive metal nanoinclusions [110,111] or Se nanorods before powder consolidation [112]. Different from the injection of conductive metal nanoinclusions that can lead to both an enhanced σ and a lower S, the injection of a reduced concentration of charge carriers into a doped semiconductor could cause a band bending that promotes electron filtering.…”

“…Apart from the highly conductive metal nanoinclusions [ 110 , 111 ], Lim et.al. has recently introduced nonmetal (Te or Se) nanodomains into a silver selenide matrix through solution blending of Ag 2 Se nanoparticles with Te or Se nanorods before powder consolidation [ 112 ].…”