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The recent advances and new insights resulting thereof in applying defect engineering to improving the thermoelectric performance and mechanical properties of inorganic materials are reviewed.

A facile pathway of the electrocatalytic nitrogen oxidation reaction (NOR) to nitrate is proposed, and Ru‐doped TiO2/RuO2 (abbreviated as Ru/TiO2) as a proof‐of‐concept catalyst is employed accordingly. Density functional theory (DFT) calculations suggest that Ruδ+ can function as the main active center for the NOR process. Remarkably doping Ru into the TiO2 lattice can induce an upshift of the d‐band center of the Ru site, resulting in enhanced activity for accelerating electrochemical conversion of inert N2 to active NO*. Overdoping of Ru ions will lead to the formation of additional RuO2 on the TiO2 surface, which provides oxygen evolution reaction (OER) active sites for promoting the redox transformation of the NO* intermediate to nitrate. However, too much RuO2 in the catalyst is detrimental to both the selectivity of the NOR and the Faradaic efficiency due to the dominant OER process. Experimentally, a considerable nitrate yield rate of 161.9 µmol h−1 gcat−1 (besides, a total nitrate yield of 47.9 µg during 50 h) and a highest nitrate Faradaic efficiency of 26.1% are achieved by the Ru/TiO2 catalyst (with the hybrid composition of RuxTiyO2 and extra RuO2 by 2.79 wt% Ru addition amount) in 0.1 m Na2SO4 electrolyte.

Sb 2 Si 2 Te 6 , a 2D material, exhibits an intrinsically high thermoelectric figure of merit ZT of 1.08 at 823 K. The thermoelectric performance can be further enhanced by a cellular nanostructure with ultrathin Si 2 Te 3 nanosheets covering the Sb 2 Si 2 Te 6 grains. The Si 2 Te 3 acts as a hole-transmitting electron-blocking filter and, at the same time, causes extra phonon scattering that leads to ultralow thermal conductivity and a high ZT value of 1.65 at 823 K.

The recent developments and trends of electrochromic conjugated polymers and their devices are highlighted in this review.

PbTe-based thermoelectric materials are some of the most promising for converting heat into electricity, but their ntype versions still lag in performance the p-type ones. Here, we introduce midgap states and nanoscale precipitates using Gadoping and GeTe-alloying to considerably improve the performance of n-type PbTe. The GeTe alloying significantly enlarges the energy band gap of PbTe and subsequent Ga doping introduces special midgap states that lead to an increased density of states (DOS) effective mass and enhanced Seebeck coefficients. Moreover, the nucleated Ga 2 Te 3 nanoscale precipitates and off-center discordant Ge atoms in the PbTe matrix cause intense phonon scattering, strongly reducing the thermal conductivity (∼0.65 W m −1 K −1 at 623 K). As a result, a high room-temperature thermoelectric figure of merit ZT ∼ 0.59 and a peak ZT max of ∼1.47 at 673 K were obtained for the Pb 0.98 Ga 0.02 Te-5%GeTe. The ZT avg value that is most relevant for devices is ∼1.27 from 400 to 773 K, the highest recorded value for n-type PbTe.

convert waste heat into electricity. [2] The thermoelectric performance is evaluated by the dimensionless figure of merit ZT of the materials, as ZT = S 2 σT/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity, respectively. [3] Over the past decades, substantial progress has been made in the development of high performance TE materials by adopting advanced processing techniques, [4] new material design concepts, [5] and band engineering [6] on traditional TE materials. In addition, pursuing new materials with unique micro/nanostructures [7] and/ or special crystal structures [8] also has proven successful in yielding high TE performance. [9] For practical applications, developing earth-abundant, lowcost TE materials with high ZT values is highly desired. In this regard, Pb-free Sn-based compounds such as SnSe, [10] SnTe, [11] Mg 2 Sn, [12] and TiNiSn [13] -based compounds are considered to be promising for medium temperature TE applications. Recently, the CdI 2 -type dichalcogenide semiconductor SnSe 2 has drawn a lot of interest due to its unique layered structure (Figure S1, Supporting Information), in which the intralayer Sn and Se atoms are covalently bonded in the ab planes and the layers are held together by interlayer van der Waals interactions along the c-axis. Thus SnSe 2 shows anisotropic electronic and optoelectronic properties. [14] More importantly, theoretical studies [15] have predicted that SnSe 2 could be a promising n-type TE material with a predicted high ZT value of 2.95 along the a-axis, while a lower ZT of 0.68 along the c-axis at 800 K with a carrier concertation of 10 20 cm −3 due to the anisotropic electrical and thermal transport properties. [16] This indicates that the orientation and carrier concentration are the key factors for high TE performance. However, only a few experimental studies on SnSe 2 have been reported, and the low carrier concentration (≈10 17 cm −3 ) and random-oriented grains still result in a low power factor (≈150 µW m −1 K −2 ) and ZT (≈0.2). [16b] Herein, we employ a defect chemistry approach [17] by simultaneously introducing a selenium (Se) deficiency and chlorine (Cl) doping in SnSe 2 nanoplate-based pellets, in which the nano plates show a preferable orientation of the (001) planes along the primary surface of the pellet (in-plane). This yields a sharp increase in the in-plane electrical conductivity and It is reported that electron doped n-type SnSe 2 nanoplates show promising thermoelectric performance at medium temperatures. After simultaneous introduction of Se deficiency and Cl doping, the Fermi level of SnSe 2 shifts toward the conduction band, resulting in two orders of magnitude increase in carrier concentration and a transition to degenerate transport behavior. In addition, all-scale hierarchical phonon scattering centers, such as point defects, nanograin boundaries, stacking faults, and the layered nanostructures, cooperate to produce very low lattice the...

The conductivity enhancement in solvent treated PEDOT:PSS is a result of the solvation of the PSS shell, leading to the release of conductive PEDOT in the core.