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Thermoelectric research has made great progress in recent years, but large-scale applications of thermoelectric materials are still far from realisation. Finding ways to improve their thermoelectric performance remains an important challenge. In4Se3 stands out as a material with exceptional thermoelectric performance and notably low thermal conductivity. However, its ZT value is constrained by the power factor. We employed first principles calculations to assess the impact of stresses on the structural and electronic properties of In4Se3. Independent elastic constants, bulk modulus B, shear modulus G, and Young's modulus E all exhibit an increase with increasing stresses. The B/G value of In4Se3 increased from 1.75 at 0 GPa to 2.12 at 5 GPa, indicating that the toughness of the material gradually increased. The calculated phonon curves show that In4Se3 demonstrates mechanical stability under both tensile stress (−1 GPa) and compressive stress (1–5 GPa) conditions. The calculated electronic structure reveals that, with increasing compressive stresses, the band gap in the PBE potential decreases from 0.15 eV at 0 GPa to 0.01 eV at 5 GPa. Similarly, in the HSE06 potential, the band gap decreases from 1.00 eV at 0 GPa to 0.73 eV at 5 GPa. Thermoelectric transport parameters of the material are calculated by solving the semi classical Boltzmann transport equation. Increasing the compressive stresses can increase both the Seebeck coefficient and the conductivity. Consequently, the power factor of In4Se3 has been greatly improved. At 700 K, the power factor can be increased by 19% in the optimal carrier range. Therefore, this study offers a theoretically viable approach to enhance the thermoelectric performance of In4Se3. [ABSTRACT FROM AUTHOR]

Bulk cobalt does not react with water at room temperature, but cobalt nanometals could yield corrosion at ambient conditions. Insights into the cobalt cluster reactions with water and oxygen enable us to better understand the interface reactivity of such nanometals. Here we report a comprehensive study on the gas-phase reactions of Con±/0 clusters with water and oxygen. All these Con±/0 clusters were found to react with oxygen, but only anionic cobalt clusters give rise to water dissociation whereas the cationic and neutral ones are limited to water adsorption. We elucidate the influences of charge states, bonding modes and dehydrogenation mechanism of water on typical cobalt clusters. It is unveiled that the additional electron of anionic Con– clusters is not beneficial to H2O adsorption, but allows for thermodynamics- and kinetics-favourable H atom transfer and dehydrogenation reactions. Apart from the charge effect, size effect and spin effect play a subtle role in the reaction process. The synergy of multiple metal sites in Con– clusters reduces the energy barrier of the rate-limiting step enabling hydrogen release. This finding of water dissociation on cobalt clusters put forward new connotations on the activity series of metals, providing new insights into the corrosion mechanism of cobalt nanometals. Cobalt-based materials have a wide range of applications from information storage to electromagnetic absorbers in aerospace manufacturing, but the corrosion of cobalt nanosurfaces is poorly explored. Here, the authors combine mass spectrometry and DFT to study gas-phase reactions of Con±/0 (n = 1–30) with water and oxygen and find that only anionic cobalt clusters give rise to water dissociation, whereas the cationic and neutral ones are limited to water adsorption. [ABSTRACT FROM AUTHOR]

The contact electrification between liquid and solid has attracted widespread attention in the fields of energy, physics and chemistry, but its basic mechanism still remains unclear, especially for charge transfer at a liquid–solid interface. Here, the droplet triboelectric nanogenerator (droplet-TENG) was used as a probe to measure the charge transfer at different sliding speeds of a moving droplet. By varying the sliding speed and concentration of the moving droplet, the transferred charges generated at a liquid–solid interface are found to be highly dependant on the sliding velocity of the droplet on the hydrophobic surface: the faster sliding speed leads to more transferred charges. However, such effect is not obvious when the droplet has higher concentration, which provides direct evidence of a "two-step" model for the formation of the electric double-layer (EDL): where electron transfer occurs when the liquid droplet contacts a hydrophobic surface for the very first time, and then ion adsorption follows. The process of surface charge transfer is probed by droplet-TENG. This work is significant for better understanding of the charge transfer at a liquid–solid interface, and devises a method to maximize tribocharging in droplet-TENG, describing a concept potentially suitable for velocity sensing applications based on the self-powered droplet-TENG. [ABSTRACT FROM AUTHOR]