Surface Functionalization of Surfactant‐Free Particles: A Strategy to Tailor the Properties of Nanocomposites for Enhanced Thermoelectric Performance

Abstract

The broad implementation of thermoelectricity requires high-performance and low-cost materials. One possibility is employing surfactant-free solution synthesis to produce nanopowders. We propose the strategy of functionalizing "naked" particles' surface by inorganic molecules to control the nanostructure and, consequently, thermoelectric performance. In particular, we use bismuth thiolates to functionalize surfactant-free SnTe particles' surfaces. Upon thermal processing, bismuth thiolates decomposition renders SnTe-Bi 2 S 3 nanocomposites with synergistic functions: 1) carrier concentration optimization by Bi doping; 2) Seebeck coefficient enhancement and bipolar effect suppression by energy filtering; and 3) lattice thermal conductivity reduction by small grain domains, grain boundaries and nanostructuration. Overall, the SnTe-Bi 2 S 3 nanocomposites exhibit peak z T up to 1.3 at 873 K and an average z T of � 0.6 at 300-873 K, which is among the highest reported for solution-processed SnTe.

Formation of a P162– Ink from Elemental Red Phosphorus in a Thiol–Amine Mixture

“…Given that some previously reported reactions between thiolates and red phosphorus or P 4 give mononuclear phosphorus compounds, this suggests that polyphosphide formation results from the specific combination of thiol and amine used here and not the phosphorus precursor. Reaction of gray arsenic and antimony in the same thiol–amine mixture produced mononuclear pnictogen–sulfide–thiolate complexes by ESI-(−)­MS, much like previous work with elemental bismuth . The synthesis of polyphosphides using red phosphorus in reagent combinations that also readily dissolve a host of other elemental sources and metals may enable further exploration and application of these species.…”

“…Analysis by ESI-(−)MS suggests that both elements react similarly to previous reports of Bi, Bi 2 O 3 , and Sb 2 S 3 in thiol–amine solutions, in which solutes consist of pnictogen–sulfide–thiolate complexes. 22 , 23 The major peak in the ESI-(−)MS spectrum of the gray arsenic solution appears at m / z 228.9 and is assigned to a complex in which arsenic exists as As(III) and is bound to two ethanethiolate ligands and a single sulfide ligand, giving the formula [C 4 H 10 AsS 3 ] − . The presence of heavier arsenic complexes may indicate that the major peak is not the parent ion but the most stable fraction of the parent ion ( Figure 3 b).…”

“…Reaction of gray arsenic and antimony in the same thiol–amine mixture produced mononuclear pnictogen–sulfide–thiolate complexes by ESI-(−)MS, much like previous work with elemental bismuth. 23 The synthesis of polyphosphides using red phosphorus in reagent combinations that also readily dissolve a host of other elemental sources and metals may enable further exploration and application of these species.…”

Thermoelectric Performance of Surface-Engineered Cu1.5–xTe–Cu2Se Nanocomposites

“…25−27 Recently, we and other groups have demonstrated surface engineering as a suitable strategy for inhibiting grain growth during spark plasma sintering (SPS), introducing grain boundary complexions, and enhancing the number of defects at multiple scales. 9,25,26 In addition, surface functionalization with different organic or inorganic molecules provides additional means to modify the electronic band structure and generate precipitated nanoinclusions as an external phase within the matrix, thereby simultaneously improving the Seebeck coefficient and reducing thermal conductivity. 20,28 Copper chalcogenides are known for their large versatilities in compositions and crystal phases.…”

“…A key challenge of sintering nano-/microsized powders is to prevent uncontrolled grain growth while still achieving full densification. While sintering and grain growth depend on surface diffusion, − surface engineering is a powerful approach to control grain growth and further adjust the final composite composition and its functional properties. − Recently, we and other groups have demonstrated surface engineering as a suitable strategy for inhibiting grain growth during spark plasma sintering (SPS), introducing grain boundary complexions, and enhancing the number of defects at multiple scales. ,, In addition, surface functionalization with different organic or inorganic molecules provides additional means to modify the electronic band structure and generate precipitated nanoinclusions as an external phase within the matrix, thereby simultaneously improving the Seebeck coefficient and reducing thermal conductivity. , …”