No abstract

Combined high performance of self-propagating synthesized materials and topological structures optimization, half-Heusler single-stage module and half-Heusler/Bi2Te3 segmented module attained record-high conversion efficiencies of 9.6% and 12.4%.

Catalytic CO2 reforming of CH4 (CRM) to produce syngas (H2 and CO) provides a promising approach to reducing global CO2 emissions and the extensive utilization of natural gas resources. However, the rapid deactivation of the reported catalysts due to severe carbon deposition at high reaction temperatures and the large energy consumption of the process hinder its industrial application. Here, a method for almost completely preventing carbon deposition is reported by modifying the surface of Ni nanocrystals with silica clusters. The obtained catalyst exhibits excellent durability for CRM with almost no carbon deposition and deactivation after reaction for 700 h. Very importantly, it is found that CRM on the catalyst can be driven by focused solar light, thus providing a promising new approach to the conversion of renewable solar energy to fuel due to the highly endothermic characteristics of CRM. The reaction yields high production rates of H2 and CO (17.1 and 19.9 mmol min−1 g−1, respectively) with a very high solar‐to‐fuel efficiency (η, 12.5%). Even under focused IR irradiation with a wavelength above 830 nm, the η of the catalyst remains as high as 3.1%. The highly efficient catalytic activity arises from the efficient solar‐light‐driven thermocatalytic CRM enhanced by a novel photoactivation effect.

Self-powered wearable electronics require thermoelectric materials simultaneously with a high dimensionless figure of merit (zT) and good flexibility to convert the heat discharged by the human body into electricity. Ag2(S,Se)-based semiconducting materials can well satisfy these requirements, and thus, they are attracting great attention in thermoelectric society recently. Ag2(S,Se) crystalizes in an orthorhombic structure or monoclinic structure, depending on the detailed S/Se atomic ratio, but the relationship between its crystalline structure and mechanical/thermoelectric performance is still unclear to date. In this study, a series of Ag2Se1‐xSx (x=0, 0.1, 0.2, 0.3, 0.4, and 0.45) samples were prepared and their mechanical and thermoelectric performance dependence on the crystalline structure was systematically investigated. x=0.3 in the Ag2Se1‐xSx system was found to be the transition boundary between orthorhombic and monoclinic structures. Mechanical property measurement shows that the orthorhombic Ag2Se1‐xSx samples are brittle while the monoclinic Ag2Se1‐xSx samples are ductile and flexible. In addition, the orthorhombic Ag2Se1‐xSx samples show better electrical transport performance and higher zT than the monoclinic samples under a comparable carrier concentration, most likely due to their weaker electron-phonon interactions. This study sheds light on the further development of flexible inorganic TE materials.

The development of zeolite-like structures with extra-large pores (>12-membered rings, 12R) has been sporadic and is currently at 30R. In general, templating via molecules leads to crystalline frameworks, whereas the use of organized assemblies that permit much larger pores produces noncrystalline frameworks. Synthetic methods that generate crystallinity from both discrete templates and organized assemblies represent a viable design strategy for developing crystalline porous inorganic frameworks spanning the micro and meso regimes. We show that by integrating templating mechanisms for both zeolites and mesoporous silica in a single system, the channel size for gallium zincophosphites can be systematically tuned from 24R and 28R to 40R, 48R, 56R, 64R, and 72R. Although the materials have low thermal stability and retain their templating agents, single-activator doping of Mn(2+) can create white-light photoluminescence.

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 consisting of the lattice thermal conductivity (κ L ) and carrier thermal conductivity (κ c ). [3] Doping external elements is a routine but effective approach to improve zT because it can tune carrier concentration or band structure to optimize PF (S 2 σ) and introduce point defects to suppress κ L . [4][5][6][7][8] However, the application of this approach highly relies on the kind and solution limit of the external elements in the host lattice. Among the numerous TE materials reported so far, GeTe is a special one because its lattice can accommodate many external elements with relatively large solution limits. Typical dopants are Sb (≈10% at Ge-sites), Bi (≈10% at Ge-sites), Pb (≈10% at Ge-sites), and Mn (>50% at Ge-sites). [9][10][11][12][13][14] Upon introducing these dopants, the κ L of GeTe can be reduced from 3.0 to around 1.0 W m −1 K −1 at 300 K. Moreover, the lattice of GeTe can simultaneously accommodate two or multiple kinds of external elements with distinct atomic mass and radius, such as (Mn, Sb), (Mn, Bi), (Cu, Sb), (In, Sb), (In, Bi), (Cr, Sb), (Ti, Sb), (Pb, Sb), and (Pb, Bi), which can further reduce the κ L to as low as 0.5 W m −1 K −1 . [15][16][17][18][19][20][21][22][23][24][25] Combining the optimized electrical transport properties by these external elements, GeTe-based compounds demonstrate high zTs in the intermediate temperature range. Among the single-doped GeTe-based compounds, Ge 0.9 Sb 0.1 Te and Ge 0.9 Bi 0.06 Te demonstrate zTs above 1.5 at 700 K. [9,10] Among the double-or multiple-doped GeTe-based compounds, Ge 0.89 Sb 0.1 In 0.01 Te, Ge 0.89 Cu 0.06 Sb 0.08 Te, Ge 0.86 Pb 0.1 Bi 0.04 Te, and Ge 0.9 Cd 0.05 Bi 0.05 Te demonstrate high zTs exceeding the level of 2.0. [15][16][17]26] Currently, GeTe-based compounds are among the best TE materials in thermoelectrics.The κ L reduction in doped GeTe-based compounds are mainly caused by the strain field and mass fluctuations introduced by the dopants. Theoretically, κ L is given by [27,28] High-efficiency thermoelectric (TE) technology is determined by the performance of TE materials. Doping is a routine approach in TEs to achieve optimized electrical properties and lowered thermal conductivity. However, how to choose appropriate dopants with desirable solution content to realize high TE figure-of-merit (zT) is very tough work. In this study, via the use of large mass and strain field fluctuations as indicators for low lattice thermal conductivity, the combination of (Mg, Bi) in GeTe is screened as very effective dopants for potentially high zTs. In experiments, a series of (Mg, Bi) co-doped GeTe compounds are prepared and the electrical and thermal transport properties are systematically investigated. Ultralow lattice thermal conductivity, about 0.3 W m −1 K −1 at 600 K, is obtained in Ge 0.9 Mg 0.04 Bi 0.06 Te due to the introduced large mass and strain field fluctuations by (Mg, Bi)...

GeTe-based compounds have been intensively studied recently due to their superior thermoelectric performance, but their real applications are still limited so far due to the drastic volume variation that occurs during the rhombohedral–cubic phase transition, which may break the material or the material/electrode interface during service. Here, superior performance and high service stability for GeTe-based thermoelectric compounds are achieved by co-doping Mg and Sb into GeTe. The linear coefficient of thermal expansion before phase transition is greatly improved to match that after phase transition, yielding smooth volume variation around the phase transition temperature. Likewise, co-doping (Mg, Sb) in GeTe successfully tunes the carrier concentration to the optimal range and effectively suppresses the lattice thermal conductivity. A peak zT of 1.84 at 800 K and an average zT of 1.2 in 300–800 K have been achieved in Ge0.85Mg0.05Sb0.1Te. Finally, a Ni/Ti/Ge0.85Mg0.05Sb0.1Te thermoelectric uni-leg is fabricated and tested, showing quite good service stability even after 450 thermal cycles between 473 K and 800 K. This study will accelerate the application of GeTe-based compounds for power generation in the mid-temperature range.

A unique Pt/CeO2 nanocomposite exhibits solar-light-driven thermocatalytic activity for CO2 reduction by methane with high light-to-fuel efficiency and production rates of H2 and CO.