Search

The retarded kinetics of oxygen evolution on electrodes is a bottleneck for electrochemical energy conversion and storage systems. NiFe-based electrocatalysts provide a cost-effective choice to confront this challenge. However, there is a lack of facile techniques for depositing compact catalytic films of high coverage and possessing a state-of-the-art performance, which is especially desired in photoelectrochemical (PEC) systems. Herein, we demonstrate a spray pyrolysis (SP) route to address this issue, featuring the kinetic selective preparation towards the desired catalytic-active material. Differing from reported SP protocols which only produce inactive oxides, this approach directly generates a unique composite film consisting of NiFe layered oxyhydroxides and amorphous oxides, exhibiting an overpotential as small as 255 mV (10 mA cm−2) and a turnover frequency of ∼0.4 s−1 per metal atom. By using such a facile protocol, the surface rate-limiting issue of BiVO4 photoanodes can be effectively resolved, resulting in a charge injection efficiency of over 90%. Considering this deposition directly start from simple nitrates but only takes several seconds to complete, we believe it can be developed as a widely applicable and welcomed functionalization technique for diverse electrochemical devices.

Direct optical polymer patterning As a platform for electronic devices, polymeric materials offer the advantages of intrinsic flexibility and stretchability relative to hard material devices. However, unlike materials such as silicon, there are few tools for large-scale patterning of monolithic devices. Zheng et al. developed an optical lithography technique for the high-throughput fabrication of transistor circuitry on stretchable substrates. In this method, ultraviolet light is used to control the local solubility of the polymer, which makes it possible to fabricate transistors on the micrometer scale. These devices can be made with high yield and excellent uniformity without compromising their electronic and mechanical characteristics. Science , abh3551, this issue p. 88

Photoelectrocatalytic (PEC) materials for harvesting solar energy can be discovered from existing photocatalytic semiconductors. Nonetheless, mixed valence tin oxides, a group of widely reported visible light active photocatalysts, can hardly be developed into efficient PEC photoelectrodes. To overcome this difficulty by clarifying its origin, two typical mixed valence tin oxides, Sn2+:SnO2 microrods and porous Sn3O4 particles were deliberately prepared as the models. Sn2+:SnO2 microrods of less porosity exhibited a photocurrent over ten times higher than Sn3O4 particles. Photo-electrochemical impedance spectroscopy revealed this was due to their charge kinetics difference, specifically the internal transport/transfer responding to the morphology. Moreover, hydroxyl residuals from synthesis were found to be very inhibitive for the PEC efficiency as well, which was in coherence with our TGA and Raman spectroscopic study. These finding experimentally proved the necessity of reconsidering the surface area, crystallinity, and defects when developing photocatalysts into efficient PEC structures.

The attractive photoelectrochemical (PEC) water splitting for hydrogen fuels always requires new semiconductors, which provide stronger visible light absorption with suitable band positions. Sn(II) complex oxides are expected to offer such new possibilities. In this work, a quaternary (Sn–Ta–W–O) Tetragonal Tungsten Bronze type Sn(II) oxide (Sn-TTB) and its photoanodes are reported for the first time. Results indicate that Sn-TTB has a bandgap of 1.85 eV with intense absorption up to 600 nm and the flat-band potential at −0.10 V vs. RHE. The IPCE of its photoanode is 10 times higher than that of the pyrochlore polymorph, owing to its better light absorption and higher carrier density. Experiments and calculations suggest strong interaction between Sn(II) ions and the W/TaO6 skeleton, facilitating the delocalization of charge carriers. Such an exploration indicates that the structural engineering of Sn(II) oxide may provide more exciting opportunities for solar energy conversion materials.

Geometrical optimization of nanowire arrays (NWAs) has been regarded as a straightforward and important route to improve the performance for photoelectrocatalytic systems but has not been realized ...

Al-ion batteries are a promising alternative to lithium-ion batteries because of the unique advantages of the Al anode, such as low cost and high specific capacities. Cathodes developed for these b...

An alternative way to mitigate the energy and environmental crisis is electrochemical CO2 reduction (ECR) into high-value products using renewable energy. Recently, Sn-based catalysts have attracted attention because of their high ECR selectivity to C1 products (HCOOH and CO). However, high overpotential, low current density, and poor stability are some issues that need to be addressed for these Sn based ECR catalysts. Resolving these problems largely depends on a comprehensive insight into the relationship between the structure and the performance of the catalysts in the ECR. In this work, we specifically compared the ECR activities and selectivities of three kinds of SnO2 nanocrystals (NCs) with different dominantly exposed facets ({111}, {221} and {110}) in an effort to elucidate their surface structure–performance relationship. We found that {111} faceted octahedral SnO2 NCs (i.e., Oct-{111} NPs) showed not only high selectivity for C1 products (>90% FE) in a wide potential range of −0.7 V to −1.0 V but also significant stability. The performance of Oct-{111} NPs was superior to that of the other two SnO2 morphologies, i.e. {221} faceted SnO2 octahedral NCs and {110}-dominantly faceted SnO2 rod-like NCs. Detailed structure and composition analysis revealed that such different ECR performances of the three SnO2 facets were mainly related to the formation of different catalytic layers on their surfaces. The findings presented here will deepen our understanding of the surface-dependent performances of Sn-based electrocatalysts in the ECR. This work provides a new strategy to construct high performance electrocatalysts through rational regulation of the metal/oxide interface.

Asymmetric molecule strategy is considered an effective method to achieve high power conversion efficiency (PCE) of polymer solar cells (PSCs). In this paper, nine oligomers are designed by combining three new electron-deficient units (unitA)—n1, n2, and n3—and three electron-donating units (unitD)—D, E, and F—with their π-conjugation area extended. The relationships between symmetric/asymmetric molecule structure and the performance of the oligomers are investigated using the density functional theory (DFT) and time-dependent density functional theory (TD–DFT) calculations. The results indicate that asymmetry molecule PEn2 has the minimum dihedral angle in the angle between two planes of unitD and unitA among all the molecules, which exhibited the advantages of asymmetric structures in molecular stacking. The relationship of the values of ionization potentials (IP) and electron affinities (EA) along with the unitD/unitA π-extend are revealed. The calculated reorganization energy results also demonstrate that the asymmetric molecules PDn2 and PEn2 could better charge the extraction of the PSCs than other molecules for their lower reorganization energy of 0.180 eV and 0.181 eV, respectively.

Two new wide-bandgap polymers (PBDTBDD-Ph and PBDTBDD-PhPh) with different aggregation degrees and fused-ring electron acceptors (FREAs) (ITIC-4T, ITIC-3T and ITIC-2T) with different sizes were synthesized. The work was used to understand how to design the donor polymers and fused-ring electron acceptors (FREAs) for high-performance non-fullerene polymer solar cells (NF-PSCs). The results clearly demonstrated that weakly aggregated donor polymers and small-sized FREAs in appropriate degrees can match well with each other to achieve high power conversion efficiencies (PCEs). In other words, small-sized FREAs can be embedded more easily into the interspace of polymer chains and weakly aggregated polymers can offer larger space for the intercalation of FREAs. As a result, an NF-PSC device based on weakly aggregated polymer PBDTBDD-Ph and small-sized ITIC-3T yielded over 11% PCE. Thus, it would offer a feasible guideline to design high-performance NF-PSCs that meet the requirement of future industry-scale production.

Oxide‐based photoelectrodes for solar water splitting have gained growing attention because of their decent stability and cost‐effectiveness. Particularly, α‐SnWO4 has been regarded as a potential next‐generation light absorbing material due to the predicted favorable bandgap of 1.9 eV. Herein, the investigation and amelioration of the crystallinity as a performance dominating factor to the α‐SnWO4‐based photoanode are demonstrated. The improvement is attributed to a unique crystallization process induced by the formation of oxygen vacancies in the reductive atmosphere at 500 °C. The sample exhibits notably enhanced visible‐light absorption and an improved charge transport property. Electrochemical measurements reveal a cathodic shift of the flat‐band potential, corresponding to the impacted band position. The photocurrent is enhanced from 0.03 to 0.42 mA cm−2 (AM1.5, 1.23 VRHE). Such a new treatment can be used as an effective tool for developing α‐SnWO4 into efficient photoelectrocatalytic (PEC) materials.

Atomically dispersed metal catalysts often exhibit superior performance compared to that of nanoparticle catalysts in many catalysis processes. However, these so-called “single-atom” catalysts have a consistently low loading density on the support surface and easily aggregate at high temperatures, hindering their practical application. Herein, we demonstrate a facile surface engineering protocol using molecule–surface charge transfer adducts to fabricate highly stable noble metal catalysts with atomic dispersion, using a Pt/CeO2 catalyst as an example. The key of this approach is the generation of an adequate amount of Ce3+ defective sites on the porous CeO2 surface through the adsorption of reductive ascorbic acid molecules and a subsequent surface charge transfer process. Subsequently, noble metal Pt atoms can be well-dispersedly anchored onto the generated Ce3+ sites of porous CeO2 nanorods with a loading density of up to 1.0 wt %. The as-prepared highly dispersed Pt/CeO2 catalyst showed outstanding ca...

Alloy nanoparticle catalysts are known to afford unique activities that can differ markedly from their parent metals, but there remains a generally limited understanding of the nature of their atomic (and likely dynamic) structures as exist in heterogeneously supported forms under reaction conditions. Notably unclear is the nature of their active sites and the details of the varying oxidation states and atomic arrangements of the catalytic components during chemical reactions. In this work, we describe multimodal methods that provide a quantitative characterization of the complex heterogeneity present in the chemical and electronic speciations of Pt–Ni bimetallic catalysts supported on mesoporous silica during the reverse water gas shift reaction. The analytical protocols involved a correlated use of in situ X-ray Absorption Spectroscopy (XAS) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), complimented by ex-situ aberration corrected Scanning Transmission Electron Microscopy (ST...

An alkyl thiophene unit was employed for the first time as a side chain substituent on an asymmetric benzodithiophene (BDT) building block in the design of novel light-harvesting polymers. A new D–A type polymer (PBDTTh–DTffBT) based on alkylthienyl asymmetric BDT and the well-known 4,7-di(thiophen-2-ethylhexyl)-5,6-difluoro-2,1,3-benzothiadiazole (DTffBT) was synthesized through a palladium catalyzed Stille coupling reaction. Efficient bulk heterojunction solar cells were fabricated by blending PBDTTh–DTffBT with PC71BM. The optimized PBDTTh–DTffBT-based photovoltaic device exhibits an open circuit voltage (VOC) of 0.87 V, a short-circuit current density (JSC) of 15.06 mA cm−2, a fill factor (FF) of 70.4% and a high power conversion efficiency (PCE) of 9.22%. The PCE was higher than the polymers which have the same backbone structure but also have the 1D or 2D symmetric BDT unit. In addition, a PCE of 7.83% with a VOC of 0.91 V, a JSC of 13.62 mA cm−2, and an FF of 63.2% was obtained for PBDTTh–DTffBT/ITIC, which is also impressive for non-fullerene PSCs. The results indicate that our design strategy of introducing an alkylthienyl unit as side chain to fabricate asymmetric BDT-based polymer is efficient in improving the photovoltaic performance.

Almost all high-performance non-fullerene polymer solar cells (NF-PSCs) require the optimization of the morphologies of active layers using additional complicated treatments, such as solvent additive processing and thermal annealing. There are still no guidelines currently available regarding controlling the morphologies of polymer donor and fused-ring acceptor blends from a structural point of view to avoid additional post-treatments. Here, we propose an efficient strategy to design polymers that can generate preferred morphologies and then be used to fabricate as-cast high-performance NF-PSCs. New asymmetric benzodithiophene (BDT) building blocks are employed to construct these polymers. The thienylthiol group with a long alkyl chain as one side substituent on BDT can modulate energy levels, broaden absorption spectra and improve solubility. For the key other side chain, bare rigid aryl rings (benzene, naphthalene and biphenyl) are used as lever arms to stir well the elongated acceptor (ITIC) phase and weaken entanglements among polymer chains during the spin-coating process, which enables favorable morphologies without any post-treatments. Finally, the polymer PBDTTAZ-NaPh yielded a power conversion efficiency (PCE) of 11.56%, which is a rare high value for as-cast NF-PSCs. Thus, it would be feasible to employ this proposed strategy to design high-performance NF-PSCs without post-treatment that meet the requirements for future industry-scale production.

In this work, we reported two wide band-gap donor–acceptor (D–A) photovoltaic materials based on asymmetric benzodithiophene units with a bare phenyl or alkoxyl chain modified phenyl group as one of the substitutions. The optical band-gaps of the two polymers are both identified above 1.80 eV. P2 (with a side chain in the phenyl group) reveals slightly red-shifted film absorption spectra compared to polymer P1 attached with the bare phenyl group, which is partly attributed to the better molecular conformations and intermolecular interactions. Polymer solar cells with different acceptor materials are fabricated to systematically evaluate the photovoltaic properties of the two polymers. The results show that P2 based fullerene and fullerene-free solar cells both show superior photovoltaic performance over the devices of P1, mainly attributed to the more favorable heterojunction morphologies and more balanced charge transport. P2 based PSCs with PC71BM as the acceptor demonstrate an enhanced efficiency (8.58%) compared to that of P1 (7.04%). Notably, low boiling point toluene was reported as an effective additive for the first time to optimize the photovoltaic performance of fullerene-free polymer solar cells. The best efficiency of the P2/ITIC based devices reached over 9%, with a VOC of 0.90 V, JSC of 16.70 mA cm−2, and FF of 0.603, suggesting the great potential of low boiling point solvents as the additive toward efficient fullerene-free polymer solar cells.

Extending π-conjugation in the benzodithiophene (BDT) side chains has been proven useful to improve the efficiencies of the BDT-based polymer solar cells (PSCs). Herein, combined with a symmetry-breaking strategy of a BDT unit, we further designed a new asymmetric 1D–2D (one dimensional–two dimensional) monomer asy-BDTBP with an alkoxyl group as the 1D part and a π-extending alkoxybiphenyl as the 2D substituted group. Medium band-gap donor–acceptor (D–A) conjugated polymer P1 was synthesized with asy-BDTBP and 4,7-di(4-(2-ethylhexyl)-2-thienyl)-5,6-difluoro-2,1,3-benzothiadiazole (DTffBT) as the donor and acceptor unit, respectively. Encouragingly, P1 blended with PC71BM exhibited an obviously enhanced power conversion efficiency (PCE) compared to the reported symmetric analogue PBDTBP–DTffBT (6.70%). The PCE increased to 8.45% with an open-circuit voltage (VOC) of 0.838 V, a short-circuit current density (JSC) of 14.35 mA cm−2 and a fill factor (FF) of 70.27%. However, P1 coupled with a classical non-fullerene acceptor ITIC revealed a relatively poor efficiency of 6.35% due to the bad complementarity of absorption spectra. To match the absorption of ITIC, a wide band-gap D–A polymer P2 was further designed with a weak electron-withdrawing group benzo[1,2-c:4,5-c′]dithiophene-4,8-dione (BDD) instead of DTffBT as the acceptor unit. As a result, P2 possessed a complementary absorption spectrum with ITIC, and the resulting devices presented an excellent photovoltaic performance. The optimal efficiency boosted to 10.04% with VOC of 0.873 V, JSC of 17.60 mA cm−2 and FF of 65.37%. This work demonstrates the great potential of asymmetric BDTs for high efficient PSCs and the importance of the rational design of polymers for different types of PSCs.

Cost-effective photoanodes with remarkable electronic properties are highly demanded for practical photoelectrochemical (PEC) water splitting. The ability to manipulate the surface carrier separation and recombination is pivotal for achieving high PEC performance for water splitting. Here, a facile and economical approach is reported for substantially improving the surface charge separation property of CdS photoanodes through in situ photoactivation, which significantly reduces surface charge recombination through the formation of thiosulfate ion which is favorable to the transfer of photogenerated holes and a uniform nanoporous morphology via the dissolving Cd2+ with phosphate ions on the surface of CdS. The resulting CdS electrodes through scalable particle transfer method exhibit nearly tripled photocurrents, with an incident-photon-to-current conversion efficiency (IPCE) at 480 nm exceeding 80% at 0.6 V versus reversible hydrogen electrode (RHE). And the CdS thin films prepared from chemical bath deposition display quadrupled photocurrents after the stir and PEC activation, with an IPCE of 91.7% at 455 nm and 0.6 V versus RHE. With the suppression of photocorrosion in alkaline borate buffer, the activated photoanodes show great stability for solar hydrogen production at the sacrifice of sulfite. This work brings insights into the design of nanoporous metal sulfide semiconductors for solar water splitting.

In this paper, we reported a crystalline p-type medium-bandgap conjugated D–A polymer asy-PBDBTN based on a symmetry-breaking-modified BDT moiety to combine the advantages of both one-dimension (1D) and two-dimension (2D) symmetric BDTs. Polymer asy-PBDBTN is a highly efficient light-harvesting donor material. Single BHJ PSCs exhibit PCE of 8.88% with PC71BM as acceptor. Also, PCE values of 10.50% are achieved with the use of ITIC as an acceptor to couple asy-PBDBTN with VOC of 0.942 V, JSC of 16.81 mA cm–2, and FF of 0.663. It is worth noting that lower energy loss is obtained in fullerene-free-based PSCs, which is essential to overcome the trade-off between VOC and JSC and boost these two parameters simultaneously for high photovoltaic performance. The combination process of additive and thermal annealing is critical to enhance and retain the π–π stacking behavior of donor and fullerene-free acceptor; as a result, the trap-assisted recombination was greatly suppressed. This work demonstrates a great pro...

In this work, 2-(3-ethyl-4-oxothiazolidin-2-ylidene)malononitrile is connected on the β position of thiophene, and this monomer is copolymerized with indacenodithiophene (IDT) to build one novel photovoltaic polymer (PIDTPCR). The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) level of the polymer is −5.26 eV and −3.45 eV, respectively. Compared with reference polymer without rhodanine side chain, PIDTPCR polymer shows low band gap and low energy level which contribute to the Jsc and Voc of the PSCs devices. The best performance parameters of the solar cells devices are Voc (0.91 V), Jsc (10.1 mA/cm2), FF (52.4%) and PCE (5.18%).

Bare naphthalene units bonded via the α- and β-positions as side chain substituents on an asymmetric benzodithiophene (BDT) building block were employed in the design of new light-harvesting polymers for the first time. Accordingly, two D–A type polymers, based on naphthyl-substituted BDT as a D-building block and the well-known 4,7-di(thiophen-2-ethylhexyl)-5,6-difluoro-2,1,3-benzothiadiazole (DTffBT) as an acceptor unit, were synthesized. The polymer PBDTβNPFBT with naphthalene bonded via the β-position exhibits an appropriate π–π distance. The naphthalene rings efficiently broaden the absorption and narrow the optical band gap (Eoptg), by extending the degree of π-conjugation, which is beneficial for capturing more photons and thus improving the short-circuit current density (JSC). Meanwhile, PBDTβNPFBT-based devices also exhibit a desirable high open circuit voltage (VOC), due to the low saturation dark current density (JS) arising from the exactly appropriate π–π distance. As a result, the power conversion efficiency (PCE) of 9.80% for the PBDTβNPFBT/PC71BM-based PSC is the highest efficiency ever obtained among the reported BDT and DTBT backbone photovoltaic polymers. In addition, a PCE of 7.33% was obtained for PBDTβNPFBT/ITIC without any treatment, which is also impressive for non-fullerene PSCs. Thus, it can be concluded that a naphthyl unit bonded via the β-position can lead to a better trade-off between Eoptg and VOC, ultimately increasing the PCE dramatically.

Two novel copolymer donors based on one-dimensional (1D)–two-dimensional (2D) asymmetrical benzodithiophene (BDT) units (BDTPH-H and BDTPH-OR) and 2,3-diphenyl-5,8-di(thiophen-2-yl)quinoxaline (DTQx) were synthesized and compared with one-dimensional or two-dimensional symmetric BDT unit based photovoltaic polymers. Both asymmetrical polymers exhibited promising photovoltaic performance compared with 1D and 2D symmetric BDT polymers. The power conversion efficiency (PCE) of PBDTPH-DTQx based polymer solar cells is 5.6%, with balanced VOC = 0.7 V, JSC = 11.89 mA cm−2 and FF = 67.3%, which is almost the highest PCE compared with similar BDT unit and fluorine-free substituted DTQx based polymer. What is more, PBDTPH-DTQx shows better performance than PBDTPHO-DTQx due to the single phenyl making DTQx more planar and with better π–π stacking than alkoxy phenyl. These findings demonstrate that the 1D–2D asymmetrical BDT units are also applicable to poor planarity fluorine-free substituted quinoxaline acceptor system.

AgPd alloy nanoparticles deposited on carbon nitride have been synthesized by a facile one-step reduction method and exhibit high catalytic activity at near room temperature (30 °C) for formic acid dehydrogenation, both under visible light and in darkness. The study proves that using the synergistic combination of alloying effects and metal-support interactions greatly enhances the catalytic activity of Pd-based nanocatalysts for hydrogen generation.

In this work, α- and β-position naphthalene substituents as side chains on asymmetric BDT were used as donor building blocks to build wide bandgap (WBG) donor materials (PαNBDT-T1 and PβNBDT-T1) with fluorinated benzotriazole (T1) as the acceptor unit. The two co-polymers were used to build polymer solar cells (PSCs) with PC71BM or ITIC acceptor material. In ITIC acceptor material based devices, the PαNBDT-T1 co-polymer with a larger dihedral angle between main backbone and naphthalene ring achieved a higher power conversion efficiency (PCE) of 9.60% with improved short-circuit current density (JSC) and fill factor (FF) compared with PβNBDT-T1, which was ascribed to the excellent morphology of the blended film. The open circuit voltage (VOC) was also maintained at a decent level upon introducing these naphthalene rings due to their high ionization potential and low electron density. Interestingly, for PC71BM based devices, the two polymers show a reverse situation compared with an ITIC system. The PβNBDT-T1 with a small dihedral angle between the main backbone and naphthalene rings shows a slightly higher performance than PαNBDT-T1. However, in the PC71BM system, both polymers did not exhibit ideal optical performance due to their unmatched absorption spectrum. These phenomena indicate that the asymmetric BDTs have great potential towards achieving high optical performance with non-fullerene acceptor materials.

Photoelectrochemical (PEC) water oxidation for sustainable clean energy and fuel production is a potential solution to the demands of organic pollutant removal and growing energy consumption. Development of high performance photoanodes, which is a key component in the system, is one of the central topics in the area. The crystal defect is an old concept but fruiting new understanding with promotive impact to the development of high performance photoanodes. In this review, we elucidated the typical defects involved in the photoanode with the position where they play the roles in the structure and how the properties of photoanode are influenced. In addition, we summarized the feasible protocols to maximize the pros but reduce the cons brought by having defects to the photoanode performance based on recent most prominent research advancements in the field. Finally, we briefly sketched the future perspective with the challenges of this topic when in the scenario of possible developments into practical applications.

Conversion of carbon monoxide to high value-added ethylene with high selectivity by traditional syngas conversion process is challenging because of the limitation of Anderson-Schulz-Flory distribution. Herein we report a direct electrocatalytic process for highly selective ethylene production from CO reduction with water over Cu catalysts at room temperature and ambient pressure. An unprecedented 52.7 % Faradaic efficiency of ethylene formation is achieved through optimization of cathode structure to facilitate CO diffusion at the surface of the electrode and Cu catalysts to enhance the C-C bond coupling. The highly selective ethylene production is almost without other carbon-based byproducts (e.g. C1 -C4 hydrocarbons and CO2 ) and avoids the drawbacks of the traditional Fischer-Tropsch process that always delivers undesired products. This study provides a new and promising strategy for highly selective production of ethylene from the abundant industrial CO.

The single-layer spherical reticulated shell structure is used as the fixed roof of a 20000 m3 internal floating roof tank. In the process of inspection and maintenance, the reticulated shell collapsed. In this paper, the strength, stiffness and stability of the design structure of the tank roof reticulated shell are calculated based on the finite element model, and the weak points of the shell structure are revealed, and the failure causes of the shell structure are comprehensively analyzed.

A steam generator at the bottom of a radiant chamber of a hydrogen production unit is used to heat the conversion gas of the reformer to the boiler feed water, thus producing medium pressure steam. During the inspection process, the color of the temperature indicating coating was found to be abnormal near the manhole block of the equipment. The maximum temperature of the wall of the device was up to 472.7°C by infrared thermal imager. In this paper, the reason of the overtemperature of the steam generator is analyzed. Secondly, the stress strength evaluation based on the conventional strength checking formula and the finite element numerical simulation analysis method is carried out. Finally, the monitoring suggestion and the follow-up test proposal under the high temperature operating condition are given.

The 2D asymmetric benzodithiophene (BDT) unit is used as a donor unit to construct one new polymer PBDTBDD-Th with benzo[1,2-c:4,5-c']dithiophene-4,8-dione (BDD) as acceptor building block. In comparison to the polymer PBDTsTh-BDD with a side chain containing a sulfur atom, the devices based on PBDTBDD-Th/ITIC show better performance due to the introduction of carbon atoms in the side chain, which could weaken the self-aggregations of polymer chains. As a result, the devices based on PBDTBDD-Th/ITIC blends yield power conversion efficiencies (PCEs) over 10%, much higher than those based on PBDTsTh-BDD/ITIC blends (7.09%). The exciton dissociation probabilities (P diss ) of a device based on PBDTBDD-Th/ITIC blends is 95.3%, which suggests that the device achieves good exciton dissociation and charge transfer. In general, the polymer PBDTBDD-Th shows capability to increase the PCEs of polymer solar cells (PSCs) with a non-fullerene acceptor.

Based on the most recently significant progress within the last one year in organic photovoltaic research from either alkylthiolation or fluorination on benzo[1,2-b: 4,5-b'] dithiophene moiety for high efficiency polymer solar cells (PSCs), two novel simultaneously fluorinated and alkylthiolated benzo[1,2-b: 4,5-b'] dithiophene (BDT)-based donor-acceptor (D-A) polymers, poly(4,8-bis(5'-((2''-ethylhexyl) thio)-4'-fluorothiophen-2'-yl) benzo[1,2-b: 4,5-b'] dithiophene-2,6-diyl)-alt-2'-ethylhexyl-3-fluorothieno[3,4-b] thiophene-2-carboxylate (PBDTT-SF-TT) and poly(4,8-bis(5'-((2''-ethylhexyl) thio)-4'-fluorothiophen-2'-yl) benzo[1,2-b: 4,5-b'] dithiophene-2,6-diyl)-alt-1,3bis( thiophen-2-yl)-5,7-bis(2-ethylhexyl) benzo[1,2-c: 4,5-c'] dithiophene-4,8-dione (PBDTT-SF-BDD), namely, via an advantageous and synthetically economic route for the key monomer are reported herein. Synergistic effects of fluorination and alkylthiolation on BDT moieties are discussed in detail, which is based on the superior balance between high V-oc and large J(sc) when PBDTTSF- TT/PC71BM and PBDTT-SF-BDD/ PC71BM solar cells present their high V-oc as 1.00 and 0.97 V (associated with their deep highest occupied molecular orbital level of -5.54 and -5.61 eV), a moderately high J(sc) of 14.79 and 14.70 mA cm(-2), and thus result a high power conversion efficiency of 9.07% and 9.72%, respectively. Meanwhile, for PBDTT-SF-TT, a very low energy loss of 0.59 eV is pronounced, leading to the promisingly high voltage, and furthermore performance study and morphological results declare an additive-free PSC from PBDTT-SF-TT, which is beneficial to practical applications.

We propose a nanostructured Mn-doped V2O5 lithium-ion battery cathode material that facilitates cathodic charge transport. The synthesis strategy uses a layered compound, vanadium(III) jarosite, as the precursor, in which the Mn2+ ions are doped uniformly between the vanadium oxide crystal layers. Through a two-step transformation, the vanadium jarosite was converted into Mn2+-doped V2O5. The resulting aliovalent doping of the larger Mn cations in the modified V2O5 structure increases the cell volume, which facilitates diffusion of Li+ ions, and introduces oxygen vacancies that improve the electronic conductivity. Comparison of the electrochemical performance in Li-ion batteries of undoped and the Mn2+-doped V2O5 hierarchical structure made from layered vanadium jarosite confirms that the Mn-doping improves ion transport to give a high cathodic columbic capacity (253 mAhg–1 at 1C, 86% of the theoretical value, 294 mAhg–1) and excellent cycling stability.

The optical resonances of plasmonic nanostructures depend critically on the geometrical details of the absorber. We show that this unique property of plasmons can potentially be used to create panchromatic absorbers covering most of the useful solar spectrum, by measuring the light-to-hydrogen conversion capabilities of a series multielectrode photocatalytic devices, based on functionalized gold nanorods of appropriately chosen aspect ratios. Judiciously combining nanorods of various aspect ratios almost doubles the H2 production of the device over what is optimally possible with a device using gold nanorods of a single aspect ratio (all other key parameters being equal). The estimated quantum efficiency (absorbed photons-to-hydrogen) averaged over the entire solar spectrum of the best performing plasmonic multielectrode array was approximately 0.1%, and the measured H2 production rate for all of the devices was found to be approximately proportional to the hot electron generation. The device was monitored continuously for over 200 hr of operation without measurable diminution in the rate.

A novel benzodithiophene-substituted benzodithiophene (crossed-BDT) with an enlarged conjugated skeleton was designed and synthesized as an electron-rich unit for the construction of donor-acceptor copolymers. Different acceptors, including 4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole (DTBT) and 4,7-di(thiophen-2-yl)-5,6-difluoro-2,1,3-benzothiadiazole (DTffBT) were used as electron-deficient units for the target copolymers to investigate the effect of the inclusion of two fluorine atoms on the acceptor unit of the polymer. The crossed-BDT and DTBT based polymers show high open circuit voltages (V-oc) of over 0.9 V with the decent power conversion efficiency (PCE) of 3.74%. The crossed-BDT and DTffBT based polymers show nearly 1 V (0.95 V) V-oc due to the fluorine induced low-lying HOMO energy level. The 0.9-0.95 V is an impressive V-oc result for a 1.7 eV band gap (E-g) polymer. To the best of our knowledge, this is the first report about a crossed conjugated benzodithiophene building block design, and this building block is effective in improving the V-oc of low band gap DBT polymers.

Two series of new polymers with medium and wide bandgaps to match fullerene (PC71 BM) and fullerene-free 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC) acceptors are designed and synthesized, respectively. For constructing the key donor building blocks, the effective symmetry-breaking strategy is employed. Two common aromatic rings (thiophene and benzene) are chosen as one side substituted groups in the asymmetric benzodithiophene (BDT) monomers. In addition, another rigid benzene ring is inserted between aryl and thioether in the side chains, which results in larger twisting and destroying the aggregation and forming longer lever arms. As a result, highly ordered polymers (PBDTsTh-FBT and PBDTsPh-FBT) with strong aggregation properties can blend well with roughly spherical PC71 BM, while amorphous polymers (PBDTsThPh-BDD and PBDTsPhPh-BDD) with long and rigid aryl rings show good miscibility with elongated ITIC, and finally, both devices exhibit excellent power conversion efficiencies over 10%. Thus, it clearly shows that the asymmetric BDT unit is an excellent donor building block to construct highly efficient photovoltaic polymers. Meanwhile, this work demonstrates that it is not necessary that high-performance fullerene-free polymer solar cells (PSCs) require highly ordered microstructures in the blending films, different from the fullerene-based PSCs.

Two tetradodeoxyphenyl-substituted indacenodithiophene (IDT) based polymers, PIDT3T and PIDTDTBT, were achieved by copolymerizing IDT with terthiophene (3T) or di-2-thienyl-2′,1′,3′-benzothiadiazole (DTBT). Although these two polymers show significantly different UV-vis absorption spectra and band gaps (2.08 eV and 1.75 eV), the HOMO levels (−5.35 eV and −5.30 eV) of these polymers are almost the same. Polymer solar cells (PSCs) based on polymers with the benzothiadiazole (BT) unit show relatively high short-circuit current density (Jsc) due to the relatively wide and high photo-electronic response and high hole mobility. Thanks to the four long aryl side chains on IDT, the polymer thin film shows an amorphous nature, and the AFM root-mean-square roughness (RMS) value of the polymer/PCBM blend film is only around 0.3 nm which can contribute to the homogenous bulk heterojunction structures without significant phase separation. Finally, decent power conversion efficiency (PCE) of 4.52% is achieved by the benzothiadiazole based polymer and PC71BM composite. By comparison study, we demonstrate why BT is an excellent acceptor unit for indacenodithiophene-based PSCs.

Two 1D-2D asymmetric benzodithiophenes (BDTs) as donor building blocks are designed and synthesized, combining the advantages of both 1D and 2D symmetric BDTs. The photovoltaic properties of the asymmetric BDT-based polymers are improved greatly in comparison with corresponding symmetric BDT-based polymers. This work provides a new approach to design prospective organic optoelectronic materials employing the symmetry-breaking strategy.

A mesoporous Bi_2Te_3 monolith with ≈20% porosity is fabricated by hot-pressing mesoporous powders. The mesostructures are able to transport carriers and scatter phonons efficiently. The reduction (≈60%) of the thermal conductivity is sufficient to compensate for the loss of electrical conductivity perpendicular to the direction of applied pressure, leading to an enhanced zT of 0.7, highest among all reported self-doped, n-type Bi_2Te_3 at similar temperatures.

NSF of China [21033007]; Ministry of Scientific and Technological Projects [2010IM040100]; 973 Program [2009CB930703]; NFFTBS [J0630429]

Summary Despite the high energy density, the lithium metal electrode has been plagued for decades with a dendrite growth problem that can result in a battery thermal runaway. Here, we introduce anisotropic spatially heterogeneous three dimensional (3D) current collectors that prevent lithium deposition on the insulating electrolyte-facing surface and accommodate lithium deposition inside the spacious voids. The anisotropic spatial heterogeneity was introduced by a line-of-sight deposition of a thin SiO2 layer onto a carbon-fiber paper. The deposited SiO2 was later converted into SiC by a magnesiothermic reaction. The SiO2 and SiC decorated 3D current collectors were confirmed dendrite-free by ex situ SEM observation after a deep lithium deposition of 28.8 C cm−2 at a high current density of 4 mA cm−2. A high lithium cycling efficiency of 94% was achieved over deep deposition (14.4 C cm−2) and stripping cycles in a carbonate based organic electrolyte, demonstrating the superiority of the novel current collector for dendrite control and lithium cycling. This strategy opens new avenues to address the dendrite problem by rationally designed current collectors and for the creation of a high energy density electrode.

Large tube type fuel heating furnaces are important and essential equipments, which have a wide range of applications in the petroleum and chemical industry, and failure modes of the furnace tubes in them are mostly caused by carburizing. It is important to improve effective detection technology for the measure of the tube carburized layer thickness, as well as the research on the comprehensive performance of furnace tubes considering the impacts of different conditions. The specifications of Φ70×6 mm HP40Nb cracking furnace tube was studied by experiment method to evaluate the effectiveness of an acoustic emission (AE) technique, which used to measure the carburized layer thickness. In the experiment, many factors were taking into account, such as different carburizing time, the response of acoustic emission attenuation to the organization changes, the magnetic field changes, and additional stress which caused by carburization are considered. The results show that the short periods strong carburizing has obviously impacts in the changes of the organization and magnetic field of the cracking furnace tube, however, it has little contribution to the acoustic emission signal attenuation.

We have developed a general synthetic route to encapsulate small molecules in monodisperse zeolitic imid-azolate framework-8 (ZIF-8) nanospheres for drug delivery. Electron microscopy, powder X-ray diffraction, and elemental analysis show that the small-molecule-encapsulated ZIF-8 nanospheres are uniform 70 nm particles with single-crystalline structure. Several small molecules, including fluorescein and the anticancer drug camptothecin, were encapsulated inside of the ZIF-8 framework. Evaluation of fluorescein-encapsulated ZIF-8 nanospheres in the MCF-7 breast cancer cell line demonstrated cell internalization and minimal cytotoxicity. The 70 nm particle size facilitates cellular uptake, and the pH-responsive dissociation of the ZIF-8 framework likely results in endosomal release of the small-molecule cargo, thereby rendering the ZIF-8 scaffold an ideal drug delivery vehicle. To confirm this, we demonstrate that camptothecin encapsulated ZIF-8 particles show enhanced cell death, indicative of internalization and intracellular release of the drug. To demonstrate the versatility of this ZIF-8 system, iron oxide nanoparticles were also encapsulated into the ZIF-8 nanospheres, thereby endowing magnetic features to these nanospheres.

An approach based on a solution-based synthesis that produces a thermally stable Ag/oxide/S₂ Te₃ -Te metal-semiconductor heterostructure is described. With this approach, a figure of merit of zT = 1.0 at 460 K is achieved, a record for a heterostructured material made using wet chemistry. Combining experiments and theory shows that the large increase in the material's Seebeck coefficient results from hot carrier filtering.

We describe an inkjet printing assisted cooperative-assembly method for high-throughput generation of catalyst libraries (multicomponent mesoporous metal oxides) at a rate of 1 000 000-formulations/hour with up to eight-component compositions. The compositions and mesostructures of the libraries can be well-controlled and continuously varied. Fast identification of an inexpensive and efficient quaternary catalyst for photocatalytic hydrogen evolution is achieved via a multidimensional group testing strategy to reduce the number of performance validation experiments (25 000-fold reduction over an exhaustive one-by-one search).

In this work, Ag(x)Te(y)-Sb(2)Te(3) heterostructured films are prepared by ligand exchange using hydrazine soluble metal chalcogenide. Because of the created interfacial barrier, cold carriers are more strongly scattered than hot ones and thereby an over 50% enhanced thermoelectric power factor (~2 μW/(cm·K(2))) is obtained at 150 °C. This shows the possibility of engineering multiphases to further improve thermoelectric performance beyond phonon scattering through a low-temperature solution processed route.

Two indacenodithiophene-based molecules with different side chains, BTIDT-C6 and BTIDT-OC12, have been designed and synthesized for solution-processed, small-molecule organic solar cells (OSCs) donor materials. By optimizing the side chains, the hole mobility of the materials is modulated, which has been proven by the organic field-effect transistor (OFET) performances. Solar cells based on BTIDT-C6 show a power conversion efficiency (PCE) of 4.83%. To the best of our knowledge, this is the first report about indacenodithiophene-based, solution-processed, small-molecule OFETs, and it is also one of the highest PCE reports for the indacenodithiophene-based, solution-processed, small-molecule OSCs. This report makes indacenodithiophene-based small molecules the third type of high-efficiency (5% PCE), solution-processed, small-molecule OSCs donor materials, in addition to benzodithiophene (BDT) and dithienosilole (DTS).