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International audience; Improvements to battery performance, reliability and lifetime are essential to meet the expansive demands for energy storage. As part of this, continuous monitoring of the dynamic chemistry inside cells offers an exciting path to minimizing parasitic reactions and maximizing sustainability. Building upon recent fibre-optic/battery innovations, we report the use of operando infrared fibre evanescent wave spectroscopy to monitor electrolyte evolution in 18650 Na-ion and Li-ion cells under real working conditions. This approach enables identification of chemical species and reveals electrolyte and additive decomposition mechanisms during cycling, thereby providing important insights into the growth and nature of the solid–electrolyte interphase, the dynamics of solvation and their complex interrelations. Moreover, by directly embedding fibres within the electrode material, we demonstrate simultaneous observations of both the material structural evolution and the Na(Li) inventory changes upon cycling. This illuminating sensing method has the power to reveal the otherwise opaque chemical phenomena occurring within each key battery component.

Transitions from the liquid to the solid state of matter are omnipresent. They form a crucial step in the industrial solidification of metallic alloy melts and are greatly influenced by the thermophysical properties of the melt. Knowledge of the thermophysical properties of liquid metallic alloys is necessary in order to gain a tight control over the solidification pathway, and over the obtained material structure of the solid. Measurements of thermophysical properties on ground are often difficult, or even impossible, since liquids are strongly influenced by earth’s gravity. Another problem is the reactivity of melts with container materials, especially at high temperature. Finally, deep undercooling, necessary to understand nucleus formation and equilibrium as well as non-equilibrium solidification, can only be achieved in a containerless environment. Containerless experiments in microgravity allow precise benchmark measurements of thermophysical properties. The electromagnetic levitator ISS-EML on the International Space Station (ISS) offers perfect conditions for such experiments. This way, data for process simulations is obtained, and a deeper understanding of nucleation, crystal growth, microstructural evolution, and other details of the transformation from liquid to solid can be gained. Here, we address the scientific questions in detail, show highlights of recent achievements, and give an outlook on future work.

Converting low-grade heat from environment into electricity shows great sustainability for mitigating the energy crisis and adjusting energy configurations. However, thermally rechargeable devices typically suffer from poor conversion efficiency when a semiconductor is employed. Breaking the convention of thermoelectric systems, we propose and demonstrate a new zinc ion thermal charging cell to generate electricity from low-grade heat via the thermo-extraction/insertion and thermodiffusion processes of insertion-type cathode (VO2-PC) and stripping/plating behaviour of Zn anode. Based on this strategy, an impressively high thermopower of ~12.5 mV K−1 and an excellent output power of 1.2 mW can be obtained. In addition, a high heat-to-current conversion efficiency of 0.95% (7.25% of Carnot efficiency) is achieved with a temperature difference of 45 K. This work, which demonstrates extraordinary energy conversion efficiency and adequate energy storage, will pave the way towards the construction of thermoelectric setups with attractive properties for high value-added utilization of low-grade heat., Low-grade heat conversion has recently emerged and displayed great promise in sustainable electronics and energy areas. Here, the authors propose a new zinc ion thermal charging cell with hybrid behaviours for high value-added conversion from heat to electricity.

Recyclable titanium dioxide (TiO2)-based photocatalytic self-cleaning films (SCFs) having a bilayer structure were prepared and assessed. These SCFs comprised two layers of fibers fabricated using an electrospinning process. The self-cleaning layer was made of acrylonitrile–butadiene–styrene (ABS) fibers with embedded TiO2 while the substrate layer was composed of fibers made by simultaneously electrospinning poly (vinyl alcohol) (PVA) and ABS. This substrate improved the mechanical strength of the SCF and provided greater adhesion due to the presence of the PVA. The experimental results showed that the hydrophobicity (as assessed by the water contact angle), photocatalytic properties and self-cleaning efficiency of the SCF were all enhanced with increasing TiO2 content in the ABS/TiO2 fibers. In addition, the introduction of the substrate layer allowed the SCFs to be applied to various surfaces and then peeled off when desired. The ABS fibers effectively improved the strength of the overall film, while deterioration of the ABS upon exposure to UV light was alleviated by the addition of TiO2. These SCFs can potentially be recycled after use in various environments, and therefore have applications in the fields of environmental protection and medical science.

Metal-assisted chemical etching (MACE) is popular due to the large-area fabrication of silicon nanowires (SiNWs) exhibiting a high aspect ratio at a low cost. The remanence of metal, i.e., silver nanoparticles (AgNPs) used in the MACE, deteriorates the device (especially solar cell) performance by acting as a defect center. The superhydrophobic behavior of nanowires (NWs) array prohibits any liquid-based solution (i.e., thorough cleaning with HNO3 solution) from removing the AgNPs. Thermal treatment of NWs is an alternative approach to reduce the Ag remanence. Sintering temperature variation is chosen between the melting temperature of bulk-Ag (962 °C) and bulk-Si (1412 °C) to reduce the Ag particles and improve the crystallinity of the NWs. The melting point of NWs decreases due to surface melting that restricts the sintering temperature to 1200 °C. The minimum sintering temperature is set to 1000 °C to eradicate the Ag remanence. The SEM–EDS analysis is carried out to quantify the reduction in Ag remanence in the sintered NWs array. The XRD analysis is performed to study the oxides (SiO and Ag2O) formed in the NWs array due to the trace oxygen level in the furnace. The TG-DSC characterization is carried out to know the critical sintering temperature at which remanence of AgNPs removes without forming any oxides. The Raman analysis is studied to determine the crystallinity, strain, and size of Si nanocrystals (SiNCs) formed on the NWs surface due to sidewalls etching. An optimized polynomial equation is derived to find the SiNCs size for various sintering temperatures.

Electrocatalytic acetylene semihydrogenation is a promising alternative to thermocatalytic acetylene hydrogenation due to its environmental benignity and economic efficiency, but its performance is far below that of the thermocatalytic reaction because of strong competition from side reactions, including hydrogen evolution, overhydrogenation and carbon–carbon coupling reactions. We develop N–heterocyclic carbene–metal complexes, with electron–rich metal centers owing to the strongly σ–donating N–heterocyclic carbene ligands, as electrocatalysts for selective acetylene semihydrogenation. Experimental and theoretical investigations reveal that the copper sites in N–heterocyclic carbene–copper facilitate the absorption of electrophilic acetylene and the desorption of nucleophilic ethylene, ultimately suppressing the side reactions during electrocatalytic acetylene semihydrogenation, and exhibit superior semihydrogenation performance, with faradaic efficiencies of ≥98 % under pure acetylene flow. Even in a crude ethylene feed containing 1 % acetylene (1 × 104 ppm), N–heterocyclic carbene–copper affords a specific selectivity of >99 % during a 100–h stability test, continuous ethylene production with only ~30 ppm acetylene, a large space velocity of up to 9.6 × 105 mL·gcat−1·h−1, and a turnover frequency of 2.1 × 10−2 s−1, dramatically outperforming currently reported thermocatalysts., This study explores N–heterocyclic carbene copper complexes toward selective electrocatalytic reduction of acetylene to ethylene. The electron–rich copper sites were found to facilitate acetylene adsorption and ethylene desorption and achieved high activity and selectivity for ethylene production.

Aqueous rechargeable metal batteries are intrinsically safe due to the utilization of low-cost and non-flammable water-based electrolyte solutions. However, the discharge voltages of these electrochemical energy storage systems are often limited, thus, resulting in unsatisfactory energy density. Therefore, it is of paramount importance to investigate alternative aqueous metal battery systems to improve the discharge voltage. Herein, we report reversible manganese-ion intercalation chemistry in an aqueous electrolyte solution, where inorganic and organic compounds act as positive electrode active materials for Mn2+ storage when coupled with a Mn/carbon composite negative electrode. In one case, the layered Mn0.18V2O5·nH2O inorganic cathode demonstrates fast and reversible Mn2+ insertion/extraction due to the large lattice spacing, thus, enabling adequate power performances and stable cycling behavior. In the other case, the tetrachloro-1,4-benzoquinone organic cathode molecules undergo enolization during charge/discharge processes, thus, contributing to achieving a stable cell discharge plateau at about 1.37 V. Interestingly, the low redox potential of the Mn/Mn2+ redox couple vs. standard hydrogen electrode (i.e., −1.19 V) enables the production of aqueous manganese metal cells with operational voltages higher than their zinc metal counterparts., Multivalent metal batteries are considered a viable alternative to Li-ion batteries. Here, the authors report a novel aqueous battery system when manganese ions are shuttled between an Mn metal/carbon composite anode and inorganic or organic cathodes.

Nature 599(7884), 234 - 238 (2021). doi:10.1038/s41586-021-03923-3, Propane dehydrogenation (PDH) to propene is an important alternative to oil-based cracking processes, to produce this industrially important platform chemical1,2. The commercial PDH technologies utilizing Cr-containing (refs. 3,4) or Pt-containing (refs. 5,6,7,8) catalysts suffer from the toxicity of Cr(vi) compounds or the need to use ecologically harmful chlorine for catalyst regeneration9. Here, we introduce a method for preparation of environmentally compatible supported catalysts based on commercial ZnO. This metal oxide and a support (zeolite or common metal oxide) are used as a physical mixture or in the form of two layers with ZnO as the upstream layer. Supported ZnO$_x$ species are in situ formed through a reaction of support OH groups with Zn atoms generated from ZnO upon reductive treatment above 550 ��C. Using different complementary characterization methods, we identify the decisive role of defective OH groups for the formation of active ZnO$_x$ species. For benchmarking purposes, the developed ZnO���silicalite-1 and an analogue of commercial K���CrO$_x$/Al$_2$O$_3$ were tested in the same setup under industrially relevant conditions at close propane conversion over about 400 h on propane stream. The developed catalyst reveals about three times higher propene productivity at similar propene selectivity., Published by Nature Publ. Group, London [u.a.]

Minimizing the wear of the surfaces exposed to mechanical shear stresses is a critical challenge for maximizing the lifespan of rotary mechanical parts. In this study, we have discovered the anti-wear capability of a series of metal nitride-copper nanocomposite coatings tested in a liquid hydrocarbon environment. The results indicate substantial reduction of the wear in comparison to the uncoated steel substrate. Analysis of the wear tracks indicates the formation of carbon-based protective films directly at the sliding interface during the tribological tests. Raman spectroscopy mapping of the wear track suggests the amorphous carbon (a-C) nature of the formed tribofilm. Further analysis of the tribocatalytic activity of the best coating candidate, MoN-Cu, as a function of load (0.25–1 N) and temperature (25 °C and 50 °C) was performed in three alkane solutions, decane, dodecane, and hexadecane. Results indicated that elevated temperature and high contact pressure lead to different tribological characteristics of the coating tested in different environments. The elemental energy dispersive x-ray spectroscopy analysis and Raman analysis revealed formation of the amorphous carbon film that facilitates easy shearing at the contact interface thus enabling more stable friction behavior and lower wear of the tribocatalytic coating. These findings provide new insights into the tribocatalysis mechanism that enables the formation of zero-wear coatings.

CO2 hydrogenation has attracted great attention, yet the quest for highly-efficient catalysts is driven by the current disadvantages of poor activity, low selectivity, and ambiguous structure-performance relationship. We demonstrate here that C3N4-supported Cu single atom catalysts with tailored coordination structures, namely, Cu–N4 and Cu–N3, can serve as highly selective and active catalysts for CO2 hydrogenation at low temperature. The modulation of the coordination structure of Cu single atom is readily realized by simply altering the treatment parameters. Further investigations reveal that Cu–N4 favors CO2 hydrogenation to form CH3OH via the formate pathway, while Cu–N3 tends to catalyze CO2 hydrogenation to produce CO via the reverse water-gas-shift (RWGS) pathway. Significantly, the CH3OH productivity and selectivity reach 4.2 mmol g–1 h–1 and 95.5%, respectively, for Cu–N4 single atom catalyst. We anticipate this work will promote the fundamental researches on the structure-performance relationship of catalysts., CO2 hydrogenation has attracted intense scientific attention yet suffers from the disadvantage of poor activity and low selectivity. Here, the authors report that Cu single atom catalysts with tailored coordination environments on C3N4 serve as highly selective catalysts for CO2 hydrogenation.

This study aimed to develop a facile synthesis procedure for heterogeneous catalysts based on organic guanidine derivatives superbases chemically grafted on silica-coated Fe3O4 magnetic nanoparticles. Thus, the three organosilanes that were obtained by reacting the selected carbodiimides (N,N′-dicyclohexylcarbodiimide (DCC), N,N′-diisopropylcarbodiimide (DIC), respectively 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) with 3-aminopropyltriethoxysilane (APTES) were used in a one-pot synthesis stage for the generation of a catalytic active protective shell through the simultaneous hydrolysis/condensation reaction with tetraethyl orthosilicate (TEOS). The catalysts were characterized by FTIR, TGA, SEM, BET and XRD analysis confirming the successful covalent attachment of the organic derivatives in the silica shell. The second aim was to highlight the capacity of microwaves (MW) to intensify the transesterification process and to evaluate the activity, stability, and reusability characteristics of the catalysts. Thus, in MW-assisted transesterification reactions, all catalysts displayed FAME yields of over 80% even after 5 reactions/activation cycles. Additionally, the influence of FFA content on the catalytic activity was investigated. As a result, in the case of Fe3O4@SiO2-EDG, a higher tolerance towards the FFA content can be noticed with a FAME yield of over 90% (for a 5% (weight) vs oil catalyst content) and 5% weight FFA content.

Converting various types of ambient mechanical energy into electricity, triboelectric nanogenerator (TENG) has attracted worldwide attention. Despite its ability to reach high open-circuit voltage up to thousands of volts, the power output of TENG is usually meager due to the high output impedance and low charge transfer. Here, leveraging the opposite-charge-enhancement effect and the transistor-like device design, we circumvent these limitations and develop a TENG that is capable of delivering instantaneous power density over 10 MW/m2 at a low frequency of ~ 1 Hz, far beyond that of the previous reports. With such high-power output, 180 W commercial lamps can be lighted by a TENG device. A vehicle bulb containing LEDs rated 30 W is also wirelessly powered and able to illuminate objects further than 0.9 meters away. Our results not only set a record of the high-power output of TENG but also pave the avenues for using TENG to power the broad practical electrical appliances., TENG suffers from two fundamental limitations: high output impedance and low charge transfer. Herein, these limitations are circumvented by leveraging the opposite-charge-enhancement effect and transistor-like device design, thereby achieving the instantaneous power density over 10 MW/m2 at the low frequency of ~ 1 Hz.

Self-healability is essential for supercapacitors to improve their reliability and lifespan when powering the electronics. However, the lack of a universal healing mechanism leads to low capacitive performance and unsatisfactory intelligence. Here, we demonstrate a multi-responsive healable supercapacitor with integrated configuration assembled from magnetic Fe3O4@Au/polyacrylamide (MFP) hydrogel-based electrodes and electrolyte and Ag nanowire films as current collectors. Beside a high mechanical strength, MFP hydrogel exhibits fast optical and magnetic healing properties arising from distinct photothermal and magneto-thermal triggered interfacial reconstructions. By growing electroactive polypyrrole nanoparticles into MFP framework as electrodes, the assembled supercapacitor exhibits triply-responsive healing performance under optical, electrical and magnetic stimuli. Notably, the device delivers a highest areal capacitance of 1264 mF cm−2 among the reported healable supercapacitors and restores ~ 90% of initial capacitances over ten healing cycles. These prominent performance advantages along with the facile device-assembly method make this emerging supercapacitor highly potential in the next-generation electronics., Self-healing property is important for supercapacitors when powering the electronics, but designing devices that possess a universal healing mechanism remains challenging. Here, the authors achieve an optically, electrically, and magnetically-responsive self-healing device with integrated configuration.

The fast-growing interest for two-dimensional (2D) nanomaterials is undermined by their natural restacking tendency, which severely limits their practical application. Novel porous heterostructures that coordinate 2D nanosheets with monolayered mesoporous scaffolds offer an opportunity to greatly expand the library of advanced materials suitable for electrochemical energy storage technologies.

Conductive rutile TiO2 has received considerable attention recently due to multiple applications. However, the permittivity in conductive, reduced or doped TiO2 appears to cause controversy with reported values in the range 100–10,000. In this work, we propose a method for measurements of the permittivity in conductive, n-type TiO2 that involves: (i) hydrogen ion-implantation to form a donor concentration peak at a known depth, and (ii) capacitance–voltage measurements for donor profiling. We cannot confirm the claims stating an extremely high permittivity of single crystalline TiO2. On the contrary, the permittivity of conductive, reduced single crystalline TiO2 is similar to that of insulating TiO2 established previously, with a Curie–Weiss type temperature dependence and the values in the range 160–240 along with the c-axis.

Rechargeable calcium batteries have attracted increasing attention as promising multivalent ion battery systems due to the high abundance of calcium. However, the development has been hampered by the lack of suitable cathodes to accommodate the large and divalent Ca2+ ions at a high redox potential with sufficiently fast ionic conduction. Herein, we report a new intercalation host which presents 500 cycles with a capacity retention of 90% and a remarkable power capability at ~3.2 V (vs. Ca/Ca2+) in a calcium battery. The cathode material derived from Na0.5VPO4.8F0.7 is demonstrated to reversibly accommodate a large amount of Ca2+ ions, forming a series of CaxNa0.5VPO4.8F0.7 (0, Rechargeable calcium batteries are promising multivalent battery systems but the lack of suitable electrodes hampers their development. Here the authors report a cathode derived from polyanion framework that demonstrates uncommonly stable and fast intercalation behaviours of calcium ions.

Recently, there are significant progresses in the growth of organic-inorganic lead halide perovskite single crystals, however, due to their susceptible nucleation and growth mechanisms and solvent requirements, the efficient and generalized growth for these single crystals is still challenging. Here we report the work towards this target with a polymer-controlled nucleation process for the highly efficient growth of large-size high-quality simple ternary, mixed-cations and mixed-halide perovskite single crystals. Among them, the carrier lifetime of FAPbBr3 single crystals is largely improved to 10199 ns. Mixed MA/FAPbBr3 single crystals are synthesized. The crucial point in this process is suggested to be an appropriate coordinative interaction between polymer oxygen groups and Pb2+, greatly decreasing the nuclei concentrations by as much as 4 orders of magnitudes. This polymer-controlled route would help optimizing the solution-based OIHPs crystal growth and promoting applications of perovskite single crystals., Research into single crystal organic-inorganic halide perovskites have gained momentum due to the potential applications, yet the growth is still a challenge. Here, the authors demonstrate a universal method based on polymer controlled nucleation process to achieve large-size and high-quality perovskite single crystals.

Aiming at laser powder bed fusion of GH3536 nickel base alloy, the effects of different scanning strategies on microstructure, porosity and mechanical properties were explored. In the aspect of microstructure and micro hardness of the sample, three scanning strategies had little difference; in the aspect of macro mechanical properties of the sample, the slope subarea scanning was better than the helix and island scanning. On this basis, the slope subarea scanning was selected as the optimal scanning strategy to form the G-surface structure, and the compression performance of G-surface was studied. The results showed that: (1) the compression performance of G-surface structure was smaller than that of solid structure, The compression strength of G-surface can only reach about 20% of solid structure: the average strength value of G-surface is 220 MPa, solid structure is 1.1 GMpa; while G-surface structure had a smooth compression curve, which indicated the good energy absorption characteristics; (2) with the increase of wall thickness, the mechanical performance of G-surface structure was also enhanced, while the energy absorption capacity was constantly reduced; (3) with the same wall thickness, the compression performance of sample in building direction (BD) is higher than that in horizontal direction (HD).

Titanium dioxide (TiO2) has a strong photocatalytic activity in the ultra-violet part of the spectrum combined with excellent chemical stability and abundance. However, its photocatalytic efficiency is prohibited by limited absorption within the visible range derived from its wide band gap value and the presence of charge trapping states located at the band edges, which act as electron–hole recombination centers. Herein, we modify the band gap and improve the optical properties of TiO2 via co-doping with hydrogen and halogen. The present density functional theory (DFT) calculations indicate that hydrogen is incorporated in interstitial sites while fluorine and chlorine can be inserted both as interstitial and oxygen substitutional defects. To investigate the synergy of dopants in TiO2 experimental characterization techniques such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray and ultra-violet photoelectron spectroscopy (XPS/UPS), UV–Vis absorption and scanning electron microscopy (SEM) measurements, have been conducted. The observations suggest that the oxide’s band gap is reduced upon halogen doping, particularly for chlorine, making this material promising for energy harvesting devices. The studies on hydrogen production ability of these materials support the enhanced hydrogen production rates for chlorine doped (Cl:TiO2) and hydrogenated (H:TiO2) oxides compared to the pristine TiO2 reference.

Single-atom-alloy catalysts (SAACs) have recently become a frontier in catalysis research. Simultaneous optimization of reactants’ facile dissociation and a balanced strength of intermediates’ binding make them highly efficient catalysts for several industrially important reactions. However, discovery of new SAACs is hindered by lack of fast yet reliable prediction of catalytic properties of the large number of candidates. We address this problem by applying a compressed-sensing data-analytics approach parameterized with density-functional inputs. Besides consistently predicting efficiency of the experimentally studied SAACs, we identify more than 200 yet unreported promising candidates. Some of these candidates are more stable and efficient than the reported ones. We have also introduced a novel approach to a qualitative analysis of complex symbolic regression models based on the data-mining method subgroup discovery. Our study demonstrates the importance of data analytics for avoiding bias in catalysis design, and provides a recipe for finding best SAACs for various applications., Single-atom metal alloys attract considerable interest as alternative metal hydrogenation catalysts. Here the authors combine first-principles calculations with compressed-sensing data-analytics approaches to develop stability and activity’s descriptors for screening single atom alloy catalysts.

Nanofluids (NFs) are colloidal suspensions of nanoparticles (NPs) within a base fluid. Unlike conventional mixtures, NFs exhibit dramatically enhanced properties, such as an abnormal increase in heat capacity at low concentration of NPs (e.g., Cp values 30% higher than the base material value). Understanding the thermo-physical behavior of NFs is essential for their application as thermal energy storage systems. In this study, we analyze a sodium nitrate ionic system containing 1 wt%, 3 wt% and 7 wt% of SiO2 NPs with different techniques like infrared thermography, infrared spectroscopy and differential scanning calorimetry (DSC) in order to shed light on the mechanism behind the increase of Cp. The themographies reveal the presence of a colder layer on top of the NF with 1 wt% of NPs whereas this layer does not appear at higher concentrations of NPs. The IR spectrum of this foamy top layer evidences the high amount of SiO2 bonds suggesting the clustering of the NPs into this layer linked by the nitrate ions. The linking is enhanced by the presence of hydroxyls in the NPs’ surface (i.e., hydroxilated NPs) that once mixed in the NF suffer ionic exchange between OH− and NO3− species, leading to O2–Si–O–NO2 species at the interface where a thermal boundary resistance or Kapitza resistance appears (RT = 2.2 m2 K kW−1). Moreover, the presence of an exothermic reactive processes in the calorimetry of the mixture with 1 wt% of NPs evidences a reactive process (ionic exchange). These factors contribute to the heat capacity increase and thus, they explain the anomalous behavior of the heat capacity in nanofluids.

Lithium ion batteries (LIBs) are at present widely used as energy storage and conversion device in our daily life. However, due to the limited power density, the application of LIBs is still restricted in some areas such as commercial vehicles or heavy-duty trucks. An effective strategy to solve this problem is to increase energy density through the development of battery materials. At the same time, a stable long cycling battery is a great demand of environmental protection and industry. Herein we present our new materials, nitrogen and boron doped carbon layer coated multiwall carbon nanotubes (NBC@MWCNTs), which can be used as anodes for LIBs. The electrochemical results demonstrate that the designed NBC@MWCNTs electrode possesses high stable capacity over an ultra-long cycling lifespan (5000 cycles) and superior rate capability even at very high current density (67.5 A g−1). Such impressive lithium storage properties could be ascribed to the synergistic coupling effect of the distinctive structural features, the reduced diffusion length of lithium ions, more active sites generated by doped atoms for lithium storage, as well as the enhancement of the electrode structural integrity. Taken together, these results indicate that the N, B-doped carbon@MWCNTs materials may have great potential for applications in next-generation high performance rechargeable batteries. National Natural Science Foundation of China Technische Universität Dresden

N-type bismuth telluride (Bi2Te3) thin films were prepared on an aluminum nitride (AlN)-coated stainless steel foil substrate to obtain optimal thermoelectric performance. The thermal co-evaporation method was adopted so that we could vary the thin film composition, enabling us to investigate the relationship between the film composition, microstructure, crystal preferred orientation and thermoelectric properties. The influence of the substrate temperature was also investigated by synthesizing two sets of thin film samples; in one set the substrate was kept at room temperature (RT) while in the other set the substrate was maintained at a high temperature, of 300 °C, during deposition. The samples deposited at RT were amorphous in the as-deposited state and therefore were annealed at 280 °C to promote crystallization and phase development. The electrical resistivity and Seebeck coefficient were measured and the results were interpreted. Both the transport properties and crystal structure were observed to be strongly affected by non-stoichiometry and the choice of substrate temperature. We observed columnar microstructures with hexagonal grains and a multi-oriented crystal structure for the thin films deposited at high substrate temperatures, whereas highly (00 l) textured thin films with columns consisting of in-plane layers were fabricated from the stoichiometric annealed thin film samples originally synthesized at RT. Special emphasis was placed on examining the nature of tellurium (Te) atom based structural defects and their influence on thin film properties. We report maximum power factor (PF) of 1.35 mW/m K2 for near-stoichiometric film deposited at high substrate temperature, which was the highest among all studied cases.

Optimal pH conditions for efficient artificial photosynthesis, hydrogen/oxygen evolution reactions, and photoreduction of carbon dioxide are now successfully achievable with catalytic bipolar membranes-integrated water dissociation and in-situ acid-base generations. However, inefficiency and instability are severe issues in state-of-the-art membranes, which need to urgently resolve with systematic membrane designs and innovative, inexpensive junctional catalysts. Here we show a shielding and in-situ formation strategy of fully-interconnected earth-abundant goethite Fe+3O(OH) catalyst, which lowers the activation energy barrier from 5.15 to 1.06 eV per HO − H bond and fabricates energy-efficient, cost-effective, and durable shielded catalytic bipolar membranes. Small water dissociation voltages at limiting current density (ULCD: 0.8 V) and 100 mA cm−2 (U100: 1.1 V), outstanding cyclic stability at 637 mA cm−2, long-time electro-stability, and fast acid-base generations (H2SO4: 3.9 ± 0.19 and NaOH: 4.4 ± 0.21 M m−2 min−1 at 100 mA cm−2) infer confident potential use of the novel bipolar membranes in emerging sustainable technologies., Bipolar membranes integrated water dissociation and acid-base generations have great potential in emerging sustainable technologies but remains inefficient. Here, the authors circumvent this inefficiency and instability of the membranes by developing polyaniline shielded catalytic bipolar membranes.

Materials databases generated by high-throughput computational screening, typically using density functional theory (DFT), have become valuable resources for discovering new heterogeneous catalysts, though the computational cost associated with generating them presents a crucial roadblock. Hence there is a significant demand for developing descriptors or features, in lieu of DFT, to accurately predict catalytic properties, such as adsorption energies. Here, we demonstrate an approach to predict energies using a convolutional neural network-based machine learning model to automatically obtain key features from the electronic density of states (DOS). The model, DOSnet, is evaluated for a diverse set of adsorbates and surfaces, yielding a mean absolute error on the order of 0.1 eV. In addition, DOSnet can provide physically meaningful predictions and insights by predicting responses to external perturbations to the electronic structure without additional DFT calculations, paving the way for the accelerated discovery of materials and catalysts by exploration of the electronic space., Computational catalysis would strongly benefit from general descriptors applicable for predicting adsorption energetics. Here the authors propose a machine-learning approach for adsorption energy predictions based on learning the relevant descriptors in a surface atom's density of states as part of the training.

Gold is a noble metal typically stable as a solid in a face-centered cubic (FCC) structure under ambient conditions; however, under particular circumstances aberrant allotropes have been synthesized. In this work, we document the phase transformation of 25 nm thick nanocrystalline (NC) free-standing gold thin-film via in situ ion irradiation studied using atomic-resolution transmission electron microscopy (TEM). Utilizing precession electron diffraction (PED) techniques, crystallographic orientation and the radiation-induced relative strains were measured and furthermore used to determine that a combination of surface and radiation-induced strains lead to an FCC to hexagonal close packed (HCP) crystallographic phase transformation upon a 10 dpa radiation dose of Au4+ ions. Contrary to previous studies, HCP phase in nanostructures of gold was stabilized and did not transform back to FCC due to a combination of size effects and defects imparted by damage cascades.

Dendrite formation, which could cause a battery short circuit, occurs in batteries that contain lithium metal anodes. In order to suppress dendrite growth, the use of electrolytes with a high shear modulus is suggested as an ionic conductive separator in batteries. One promising candidate for this application is Li7La3Zr2O12 (LLZO) because it has excellent mechanical properties and chemical stability. In this work, in situ scanning electron microscopy (SEM) technique was employed to monitor the interface behavior between lithium metal and LLZO electrolyte during cycling with pressure. Using the obtained SEM images, videos were created that show the inhomogeneous dissolution and deposition of lithium, which induce dendrite growth. The energy dispersive spectroscopy analyses of dendrites indicate the presence of Li, C, and O elements. Moreover, the cross-section mapping comparison of the LLZO shows the inhomogeneous distribution of La, Zr, and C after cycling that was caused by lithium loss near the Li electrode and possible side reactions. This work demonstrates the morphological and chemical evolution that occurs during cycling in a symmetrical Li–Li cell that contains LLZO. Although the superior mechanical properties of LLZO make it an excellent electrolyte candidate for batteries, the further improvement of the electrochemical stabilization of the garnet–lithium metal interface is suggested.

A series of La1-xCexCoO3 perovskite nanoparticles with rhombohedral phases was synthesized via sol–gel chemical process. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Electron Diffraction Spectroscopy (EDS), Thermogravimetric Analysis (TGA), UV–Vis spectroscopy, Fourier Transform Infrared spectra (FTIR), Nitrogen Adsorption/desorption Isotherm, Temperature Program Reduction/Oxidation (TPR/TPO), X-ray Photoelectron Spectroscopy (XPS) techniques were utilized to examine the phase purity and chemical composition of the materials. An appropriate doping quantity of Ce ion in the LaCoO3 matrix have reduced the bond angle, thus distorting the geometrical structure and creating oxygen vacancies, which thus provides fast electron transportation. The reducibility character and surface adsorbed oxygen vacancies of the perovskites were further improved, as revealed by H2-TPR, O2-TPD and XPS studies. Furthermore, the oxidation of benzyl alcohol was investigated using the prepared perovskites to examine the effect of ceria doping on the catalytic performance of the material. The reaction was carried out with ultra-pure molecular oxygen as oxidant at atmospheric pressure in liquid medium and the kinetics of the reaction was investigated, with a focus on the conversion and selectivity towards benzaldehyde. Under optimum reaction conditions, the 5% Ce doped LaCoO3 catalyst exhibited enhanced catalytic activity (i.e., > 35%) and selectivity of > 99%, as compared to the other prepared catalysts. Remarkably, the activity of catalyst has been found to be stable after four recycles.

Carbon-based supercapacitors have aroused ever-increasing attention in the energy storage field due to high conductivity, chemical stability, and large surface area of the investigated carbon active materials. Herein, eucalyptus-derived nitrogen/oxygen doped hierarchical porous carbons (NHPCs) are prepared by the synergistic action of the ZnCl2 activation and the NH4Cl blowing. They feature superiorities such as high specific surface area, rational porosity, and sufficient N/O doping. These excellent physicochemical characteristics endow them excellent electrochemical performances in supercapacitors: 359 F g−1 at 0.5 A g−1 in a three-electrode system and 234 F g−1 at 0.5 A g−1 in a two-electrode system, and a high energy density of 48 Wh kg−1 at a power density of 750 W kg−1 accompanied by high durability of 92% capacitance retention through 10,000 cycles test at a high current density of 10 A g−1 in an organic electrolyte. This low-cost and facile strategy provides a novel route to transform biomass into high value-added electrode materials in energy storage fields.

Single-atom metal-nitrogen-carbon (M-N-C) catalysts have sparked intensive interests, however, the development of an atomically dispersed metal-phosphorus-carbon (M-P-C) catalyst has not been achieved, although molecular metal-phosphine complexes have found tremendous applications in homogeneous catalysis. Herein, we successfully construct graphitic phosphorus species coordinated single-atom Fe on P-doped carbon, which display outstanding catalytic performance and reaction generality in the heterogeneous hydrogenation of N-heterocycles, functionalized nitroarenes, and reductive amination reactions, while the corresponding atomically dispersed Fe atoms embedded on N-doped carbon are almost inactive under the same reaction conditions. Furthermore, we find that the catalytic activity of graphitic phosphorus coordinated single-atom Fe sharply decreased when Fe atoms were transformed to Fe clusters/nanoparticles by post-impregnation Fe species. This work can be of fundamental interest for the design of single-atom catalysts by utilizing P atoms as coordination sites as well as of practical use for the application of M-P-C catalysts in heterogeneous catalysis., Phosphorus ligands have been extensively used in metal complexes for homogeneous catalysis. Here, the authors broaden this scope to heterogeneous catalysis by preparing a P-coordinated Fe single atom catalyst with excellent catalytic performance in hydrogenative transformations.

Dielectric polymers for electrostatic energy storage suffer from low energy density and poor efficiency at elevated temperatures, which constrains their use in the harsh-environment electronic devices, circuits, and systems. Although incorporating insulating, inorganic nanostructures into dielectric polymers promotes the temperature capability, scalable fabrication of high-quality nanocomposite films remains a formidable challenge. Here, we report an all-organic composite comprising dielectric polymers blended with high-electron-affinity molecular semiconductors that exhibits concurrent high energy density (3.0 J cm−3) and high discharge efficiency (90%) up to 200 °C, far outperforming the existing dielectric polymers and polymer nanocomposites. We demonstrate that molecular semiconductors immobilize free electrons via strong electrostatic attraction and impede electric charge injection and transport in dielectric polymers, which leads to the substantial performance improvements. The all-organic composites can be fabricated into large-area and high-quality films with uniform dielectric and capacitive performance, which is crucially important for their successful commercialization and practical application in high-temperature electronics and energy storage devices., Dielectric polymers are widely used in electrostatic energy storage but suffer from low energy density and efficiency at elevated temperatures. Here, the authors show that all-organic composites containing high-electron-affinity molecular semiconductors exhibit excellent capacitive performance at 200 °C.

In transition metal (M) compounds, the partial substitution of the host transition metal (Mh) to guest one (Mg) is effective to improve the functionality. To microscopically comprehend the substitution effect, degree of distribution of Mg is crucial. Here, we propose that a systematic EXAFS analysis against the Mg concentration can reveal the spatial distribution of Mg. We chose NaCo1−xFexO2 as a prototypical M compound and investigated the local intermetal distance around the guest Fe [dFe–M(x)] against Fe concentration (x). dFe–M(x) steeply increased with x, reflecting the larger ionic radius of high-spin Fe3+. The x-dependence of dFe–M(x) was analyzed by an empirical equation, $${d}_{\mathrm{F}\mathrm{e}-M}(x)=sxd_{\mathrm{F}\mathrm{e}-\mathrm{F}\mathrm{e}}+(1-sx)d_{\mathrm{F}\mathrm{e}-\mathrm{C}\mathrm{o}}$$dFe-M(x)=sxdFe-Fe+(1-sx)dFe-Co, where dFe–Fe and dFe–Co are the Fe–Fe and Co–Fe distances, respectively. The parameter s represents degree of distribution of Fe; s = 1, > 1, s value (= 4.8) indicates aggregation tendency of guest Fe.

Redox-active organic molecules have drawn extensive interests in redox flow batteries (RFBs) as promising active materials, but employing them in nonaqueous systems is far limited in terms of useable capacity and cycling stability. Here we introduce azobenzene-based organic compounds as new active materials to realize high-performance nonaqueous RFBs with long cycling life and high capacity. It is capable to achieve a stable long cycling with a low capacity decay of 0.014% per cycle and 0.16% per day over 1000 cycles. The stable cycling under a high concentration of 1 M is also realized, delivering a high reversible capacity of ~46 Ah L−1. The unique lithium-coupled redox chemistry accompanied with a voltage increase is observed and revealed by experimental characterization and theoretical simulation. With the reversible redox activity of azo group in π-conjugated structures, azobenzene-based molecules represent a class of promising redox-active organics for potential grid-scale energy storage systems., Organic molecules are promising active materials for nonaqueous redox-flow batteries (RFBs), but suffer from poor cycling stability. Here, the authors introduce azobenzene-based molecules as new type of highly soluble and stable active materials to realize high-capacity and long-life nonaqueous RFBs.

The photocatalytic activity of the ZnO NRs/CuO composite film was investigated by using both experimental and numerical methods. The ZnO NRs/CuO composite film exhibits significantly enlarge absorption range to visible-light and suppress the recombination rate of the photogenerated electron-hole pairs, which can be well utilized as a photocatalyst. The ZnO NRs/CuO composite film also presents good stability, and reusability, and durability for photo-decomposition purpose. The optimal ZnO NRs/CuO composite film contains 1μ-thick of CuO film and 10 nm-thick of ZnO NRs film. The donor concentration in ZnO NRs film should be lower than 1016 cm−3. The short circuit current density of the optimal composite film is 25.8 mA/cm2 resulting in the calculated pseudo-order rate constant of 1.85 s−1. The enhancement in degradation efficiency of this composite film is attributed to the inner electric field and large effective surface area of ZnO NRs film.

The presence of Magnéli phases in titanium oxide nanotubes (NTs) can open up frontiers in many applications owing to their electrical and optical properties. Synthesis of NTs with Magnéli phases have posed a challenge due to the degradation and loss of morphology in NTs upon high-temperature treatments (>600 °C) in a reducing environment. This study reports on the synthesis of anodically formed NTs containing Magnéli phases through a double annealing route: oxygen (O2) annealing followed by annealing in 2% hydrogen with a nitrogen balance (2%H2-N2). The nucleation, growth, and transformation of anodized amorphous NTs into crystalline phases was investigated. The NTs obtained through this route were highly ordered and composed of mixed phases of anatase, rutile, and the Magnéli phase (Ti4O7). Experimental results from scanning electron microscopy (SEM), X-ray diffraction (XRD), scanning transmission electron microscopy (S/TEM), and Raman spectroscopy were combined with first principle calculations to develop an understanding of the sequential phase transformations during annealing. A predictive model was developed using density functional theory (DFT) to potentially predict the titanium oxides formed and their stability with reference to the mole fraction of oxygen. The change in the density of states (DOS), band structure, optical properties, and stability of phases are also discussed using DFT simulations. The combination of experimental characterization and modelling helped to understand the nucleation of anatase and rutile and the reorganization of these phases to form Magnéli phases on the anodized amorphous NTs through annealing treatment.

In order to bridge the gap between theoretical and practical energy density in sodium oxygen batteries challenges need to be overcome. In this work, four commercial air cathodes were selected, and the impacts of their morphologies, structure and chemistry on their performance with a pyrrolidinium-based ionic liquid electrolyte are evaluated. The highest discharge capacity was found for a cathode with a pore size ca. 6 nm; this was over 100 times greater than that delivered by a cathode with a pore size less than 2 nm. The air cathode with the highest specific surface area and the presence of a microporous layer (BC39) exhibited the highest specific capacity (0.53 mAh cm−2).

While most selective emitter materials are inadequate or inappropriate for building applications, here we present a techno-economically viable optical coating by integrating glass bubbles within a polymer film. A controlled glass bubble volume concentration from 0 to 70% leads to a selective solar reflectivity increase from 0.06 to 0.92 while the mid-infrared emissivity remains above 0.85. Outdoor measurements show the polymer coating on a concrete surface can provide a temperature reduction up to 25 °C during the day when conduction and convection are limited and a net cooling power greater than 78 W/m2 at a cost less than $0.005/W. The impact of polymer coating on common buildings is estimated as potential annual energy savings of 2–12 MJ/m2 and CO2 emission savings of 0.3–1.5 kg/m2. More savings are expected for higher surface-area-to-volume-ratio buildings, and the polymer coating is also expected to resolve cooling issues for old buildings with no air conditioning.