The carrier transport and optical properties of the hybrid organic-inorganic perovskite CH3NH3PbI3 are investigated using first-principles approaches. We found that the electron and hole mobilities ...could reach surprisingly high values of 7-30 × 10(3) and 1.5-5.5 × 10(3) cm(2) V(-1) s(-1), respectively, and both are estimated to be much higher than the current experimental measurements. The high carrier mobility is ascribed to the intrinsically small effective masses of anti-bonding band-edge states. The above results imply that there is still space to improve the performance of related solar cells. This material also has a sharp photon absorption edge and an absorption coefficient as high as 10(5) cm(-1), both of which contribute to effective utilization of solar radiation. Although band-edge states are mainly derived from the inorganic ions of Pb and I, thermal movement of the organic base has indirect influences on the bandgap and carrier effective masses, resulting in the temperature-dependent solar cell efficiencies.
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•A novel ultrafine nanobiosorbent of cerium modified chitosan (Ce-CNB) was prepared.•The Ce-CNB possessed properties for simultaneous oxidation and adsorption As(III).•Adsorption of ...As(III) by Ce-CNB was in high efficiency.•Mechanisms for As(III) adsorption on Ce-CNB were elucidated.
Since most existing arsenic removal adsorbents are difficult to effectively remove arsenite (As(III)), an urgent need is to develop an efficient adsorbent for removing As(III) from contaminated water. In this study, a novel ultrafine nanobiosorbent of cerium modified chitosan (Ce-CNB) with simultaneous oxidation and adsorption As(III) performance has been successfully developed. The resulting Ce-CNB with or without As(III) adsorption was characterized by FTIR, XRD, SEM, EDS, TEM, EMI and XPS analysis. Batch of adsorption experiments were performed to investigate the effects of various conditions on the As(III) adsorption. The adsorption behaviors were well described by the Langmuir isotherm and the pseudo-second-order kinetic model, with the maximum adsorption capacities of 57.5mgg−1. The adsorption mechanisms for As(III) were (i) formed monodentate and bidentate complexes between hydroxyl groups and arsenite; and (ii) partial As(III) oxidized to As(V) followed by simultaneously adsorbed on the surface of Ce-CNB. This novel nanocomposite can be reused while maintaining a high removal efficiency and can be applied to treat 5.8L of As(III)-polluted water with the effluent concentration lower than the World Health Organization standard, which suggests its great potential to remove As(III) from contaminated water.
Chitin is a major component of the exoskeleton and the peritrophic matrix of insects. It forms complex structures in association with different assortments of cuticle and peritrophic matrix proteins ...to yield biocomposites with a wide range of physicochemical and mechanical properties. The growth and development of insects are intimately coupled with the biosynthesis, turnover, and modification of chitin. The genes encoding numerous enzymes of chitin metabolism and proteins that associate with and organize chitin have been uncovered by bioinformatics analyses. Many of these proteins are encoded by sets of large gene families. There is specialization among members within each family, which function in particular tissues or developmental stages. Chitin-containing matrices are dynamically modified at every developmental stage and are under developmental and/or physiological control. A thorough understanding of the diverse processes associated with the assembly and turnover of these chitinous matrices offers many strategies to achieve selective pest control.
There are conflicting arguments about the relationship between quality management (QM) and innovation. Few studies have considered the role of organization context in influencing QM for innovation ...achievement. Taking a multi-dimensional view of QM, this study develops a research framework that examines relationships among organization contextual factors (centralization of authority and integration between functions), two dimensions of QM (hard QM and soft QM), and innovation performance (speed of new product introduction and product innovativeness). Survey data were collected from 238 plants in three industries across eight countries, and structural equation modeling was used to test the framework. Our results indicate that two QM dimensions respectively mediate the effect of contextual factors on innovation performance. Hard QM directly influences speed of new product introduction, while soft QM directly influences product innovativeness. Centralization of authority facilitates hard QM but impedes soft QM, while a high level of integration between functions is favorable to both hard QM and soft QM. A decentralized structure combined with strong integration between functions is beneficial for fostering product innovativeness through soft QM. Some other managerial implications are discussed in this study as well.
Lithium (Li) metal anodes have regained intensive interest in recent years due to the ever-increasing demand for next-generation high energy battery technologies. Li metal, unfortunately, suffers ...from poor cycling stability and low efficiency as well as from the formation of dangerous Li dendrites, raising safety concerns. Utilizing solid-state electrolytes (SSEs) to prevent Li dendrite growth provides a promising approach to tackle the challenge. However, recent studies indicate that Li dendrites easily form at high current densities, which calls for full investigation of the fundamental mechanisms of Li dendrite formation within SSEs. Herein, the origin and evolution of Li dendrite growth through SSEs have been studied and compared by using Li
6.1
Ga
0.3
La
3
Zr
2
O
12
(LLZO) and NASICON-type Li
2
O–Al
2
O
3
–P
2
O
5
–TiO
2
–GeO
2
(LATP) pellets as the separators. We discover that a solid electrolyte interphase (SEI)-like interfacial layer between Li and SSE plays a critical role in alleviating the growth of dendritic Li, providing new insights into the interface between SSE and Li metal to enable future all solid-state batteries.
Harvesting heat from the environment into electricity has the potential to power Internet-of-Things (IoT) sensors, freeing them from cables or batteries especially for use as wearable devices. We ...demonstrate a giant positive thermopower of 17.0 mV K
in a flexible, quasi-solid state, ionic thermoelectric material using synergistic thermodiffusion and thermogalvanic effects. The ionic thermoelectric material is a gelatin matrix modulated with ions providers (KCl, NaCl, and KNO
) for thermodiffusion effect and redox couple (Fe(CN)
/Fe(CN)
) for thermogalvanic effect. A proof-of-concept wearable device consisting of 25 unipolar elements generated over 2 V and a peak power of 5 μW using body heat. This ionic gelatin shows promises for environmental heat-to-electric energy conversion utilizing ions as energy carriers.
Bi2Te3‐based compounds and derivatives are milestone materials in the fields of thermoelectrics (TEs) and topological insulators (TIs). They have highly complex band structures and interesting ...lattice dynamics, which are favorable for high TE performance as well as strong spin orbit and band inversion underlying topological physics. This review presents rational calculations of properties related to TEs and provides theoretical guidance for improving the TE performance of Bi2Te3‐based materials. Although the band structures of these TE materials have been studied theoretically and experimentally for many years, there remain many controversies on band characteristics, especially the locations of band extrema and the exact values of bandgaps. Here, the key factors in the theoretical investigations of Bi2Te3, Bi2Se3, Sb2Te3, and their solid solutions are reviewed. The phonon spectra and lattice thermal conductivities of Bi2Te3‐based materials are discussed. Electronic and phonon structures and TE transport calculations are discussed and reported in the context of better establishing computational parameters for these V2VI3‐based materials. This review provides a useful guidance for analyzing and improving TE performance of Bi2Te3‐based materials.
The key factors in the first‐principles calculations for (Bi1–xSbx)2(Te1–ySey)3 are reviewed. Local‐density approximation is more accurate in the band structure calculations of relaxed Te‐based compounds due to the reasonable treatment in van der Waals force. The modified Becke–Johnson correction is needed for Bi2Se3.The low lattice thermal conductivities of Bi2Te3‐based compounds are related to the low group velocity and lifetime.
Hybrid nanocomposites containing carbon nanotubes (CNTs) and ordered polyaniline (PANI) have been prepared through an in situ polymerization reaction using a single-walled nanotube (SWNT) as template ...and aniline as reactant. TEM, SEM, XRD, and Raman analyses show that the polyaniline grew along the surface of CNTs forming an ordered chain structure during the SWNT-directed polymerization process. The SWNT/PANI nanocomposites show both higher electrical conductivity and Seebeck coefficient as compared to pure PANI, which could be attributed to the enhanced carrier mobility in the ordered chain structures of the PANI. The maximum electrical conductivity and Seebeck coefficient of composites reach 1.25 × 104 S m−1 and 40 μV K−1, respectively, and the maximum power factor is up to 2 × 10−5 W m−1 K−2, more than 2 orders of magnitude higher than the pure polyaniline. This study suggests that constructing highly ordered chain structure is a novel and effective way for improving the thermoelectric properties of conducting polymers.
Abstract
Photochemical conversion of CO
2
into high-value C
2+
products is difficult to achieve due to the energetic and mechanistic challenges in forming multiple C-C bonds. Herein, an efficient ...photocatalyst for the conversion of CO
2
into C
3
H
8
is prepared by implanting Cu single atoms on Ti
0.91
O
2
atomically-thin single layers. Cu single atoms promote the formation of neighbouring oxygen vacancies (V
O
s) in Ti
0.91
O
2
matrix. These oxygen vacancies modulate the electronic coupling interaction between Cu atoms and adjacent Ti atoms to form a unique Cu-Ti-V
O
unit in Ti
0.91
O
2
matrix. A high electron-based selectivity of 64.8% for C
3
H
8
(product-based selectivity of 32.4%), and 86.2% for total C
2+
hydrocarbons (product-based selectivity of 50.2%) are achieved. Theoretical calculations suggest that Cu-Ti-V
O
unit may stabilize the key *CHOCO and *CH
2
OCOCO intermediates and reduce their energy levels, tuning both C
1
-C
1
and C
1
-C
2
couplings into thermodynamically-favourable exothermal processes. Tandem catalysis mechanism and potential reaction pathway are tentatively proposed for C
3
H
8
formation, involving an overall (
20
e
−
–
20
H
+
) reduction and coupling of three CO
2
molecules at room temperature.
Understanding thermal and phonon transport in solids has been of great importance in many disciplines such as thermoelectric materials, which usually requires an extremely low lattice thermal ...conductivity (LTC). By analyzing the finite-temperature structural and vibrational characteristics of typical thermoelectric compounds such as filled skutterudites and Cu ₃SbSe ₃, we demonstrate a concept of part-crystalline part-liquid state in the compounds with chemical-bond hierarchy, in which certain constituent species weakly bond to other part of the crystal. Such a material could intrinsically manifest the coexistence of rigid crystalline sublattices and other fluctuating noncrystalline sublattices with thermally induced large-amplitude vibrations and even flow of the group of species atoms, leading to atomic-level heterogeneity, mixed part-crystalline part-liquid structure, and thus rattling-like thermal damping due to the collective soft-mode vibrations similar to the Boson peak in amorphous materials. The observed abnormal LTC close to the amorphous limit in these materials can only be described by an effective approach that approximately treats the rattling-like damping as a “resonant” phonon scattering.
Significance Materials with chemical-bond hierarchy may have a specially mixed part-crystalline part-liquid state and show nontraditional thermal transports beyond the traditional “small-parameter” lattice dynamics approach, especially the rattling-like thermal damping and thus an unusual lattice thermal conductivity that can only be described by including an effective “resonant” phonon scattering.
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