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As a viable replacement to commercial graphite anodes, silicon (Si) anodes have gained much attention from academics because of their considerable theoretical specific capacity and appropriate reaction voltage. Nevertheless, some limitations still exist in developing silicon anodes, including significant volume expansion and poor electrical conductivity. Herein, the carbon nanotubes (CNTs) interconnected yolk-shell silicon/carbon anodes (YS-Si@CoNC) were prepared via the chelation competition induced polymerization (CCIP) approach. The YS-Si@CoNC anode, designed in this study, demonstrates improved performance. At the current density of 0.5 A g−1 and 1 A g−1, a capacity of 1001 mAh g−1 and 956.5 mAh g−1 can be achieved after 150 cycles and after 300 cycles, respectively. In particular, at the current density of 5 A g−1, the reversible specific capacity of 688 mAh g−1 is realized. The exceptional outcomes are mainly attributed to the internal voids that adequately alleviate the volumetric expansion and the CNTs and carbon shells that provide an efficient conducting matrix to fasten the diffusion of electrons and lithium-ions. Our research presents a convenient way of designing Si/C anode materials with a yolk-shell structure to guarantee impressive electrical conductivity and robust structural integrity for high-performance LIBs.

Glucose conversion assisted photocatalytic water splitting technology to simultaneously produce H2 and high value-added chemicals is a promising method for alleviating the energy shortage and environmental crisis. In this work, we constructing type II heterojunction by in-situ coupling Zn0.3Cd0.7S quantum dots (ZCS QDs) on three-dimensionally ordered microporous CaTiO3 (3DOM CTO) for photocatalytic H2 production and glucose conversion. The DFT calculations demonstrate that substitution of Zn on the Cd site improves the separation and transmission of photogenerated carriers. Therefore, 3DOM CTO-ZCS composite exhibits best H2 production performance (2.81 mmol g-1h−1) and highest apparent quantum efficiency (AQY) (5.56 %) at 365 nm, which are about 47 and 18 times that of CTO nanoparticles (NPs). The improved catalytic performance ascribed to not only good mass diffusion and exchange, highly efficient light harvesting of 3DOM structure, but also the efficient charges separation of type Ⅱ heterojunction. The investigation on photocatalytic mechanism indicates that the glucose is mainly converted to gluconic acid and lactic acid, and the control reaction step is gluconic acid to lactic acid. The selectivity for gluconic acid on 3DOM CTO-ZCS is 85.65 %. Our work here proposes a green sustainable method to achieve highly efficient H2 production and selective conversion of glucose to gluconic acid.

The epoxidation reaction over titanium silicalite-1 (TS-1) zeolites is a green way to produce epoxides that are important intermediates for chemicals. Nevertheless, the conventional microporous TS-1 zeolite shows limited diffusion ability for bulky molecules, leading to poor activity and low selectivity. Constructing hierarchical porosity in microporous materials is an effective strategy to enhance the diffusion properties of catalysts. However, there are few reports on the design and synthesis of TS-1 zeolites with hierarchical structure featuring multilevels, interconnectivity, and regularity for efficient diffusion and epoxidations. Herein, hierarchical TS-1 zeolites with ordered macro-meso-microporosity (OMMM-TS-1) are obtained by a method combining a templated effect of ordered macro-mesoporous matrices and a confined in situ crystallization process. The OMMM-TS-1 possesses ordered macropores with tunable size (∼200-600 nm), ordered mesopores (∼8 nm), and intact micropores (∼0.5 nm). The OMMM-TS-1 achieves a cyclooctene conversion as 3.6 times and 1.8 times and a selectivity to epoxy product as 1.6 times and 1.3 times higher than the conventional TS-1 (C-TS-1) and nanosized TS-1 (Nano-TS-1) zeolites, respectively. The OMMM-TS-1 also outperforms the C-TS-1 and Nano-TS-1 zeolites in epoxidations of a series of alkenes. Such a novel hierarchical structure can be applied in the design and synthesis of many other catalysts.

For the first time, we demonstrate a Ti-MOF (Ti-metal organic framework) single-crystal featuring an intracrystal macro-microporous hierarchy (Hier-NTU-9) by a vapor-assisted polymer-templated method. This Hier-NTU-9 possesses macropores (100-1000 nm) derived from polymer templates and enhanced transport ability of bulky molecules, exhibiting almost double the desulfurization activity compared to the conventional NTU-9.

The high specific capacity and voltage of Li-rich Mn-based oxides make them promising cathode materials for high-energy-density lithium-ion batteries (LIBs). However, the problems such as low initial coulombic efficiency, fast capacity and voltage fading, poor kinetics, large voltage hysteresis, and poor safety performance hamper their fast commercialization. Herein, we report one-pot K+ and PO43− co-doping Li-rich Mn-based oxides Li1.2Ni0.13Co0.13Mn0.54O2 cathode material to improve the electrochemical performance of the lithium-ion battery. On the one hand, K+ doping can stabilize the bulk structure and enlarge the Li slabs to facilitate the diffusion of Li+, resulting in enhanced cycling and rate performance. On the other hand, PO43− doping changes the electronic structure of the material and weakens the covalency of TM-O, decreasing the irreversible loss of lattice oxygen and stabilizing the structure. As a result, the K+ and PO43− co-doping can effectively alleviate the capacity and voltage decay and the modified sample shows better cycling stability (88.6%@0.5 C@250 cycles) and rate performance (155.5 mAh g −1@5 C) compared to the pristine material. Our strategy here provides a facile one-pot method to modify Li-rich Mn-based oxides cathode material for high-performance LIBs.

Metal sulfides have attracted much attentions as anode materials for lithium-ion batteries (LIBs) because of the high theoretical capacity. However, the poor electronic conductivity and large volume variation usually give rise to the rapid capacity decay and undesirable rate performance, severely hampering their practical application. Herein, a gradient selenium-doped hollow sandwich structured zinc sulfide/carbon (ZnS/C) composite (Se-HSZC) is designed and fabricated as long life-span and stable anode material for LIBs. The gradient Se-doping enhances the interfacial charge transfer in Se-HSZC, while the unique double carbon shell sandwich structure further greatly reduces the volume expansion and ensures the electron fast transportation. Consequently, the Se-HSZC anode presents outstanding rate capability (654 mAh g−1 at 2 A g−1) with remarkable reversible capacity (567 mAh g−1 after 1500 cycles at 4 A g−1) for the half battery. In particular, a reversible capacity of 457 mAh g−1 at 0.5 A g−1 is achieved after 50 cycles for the full battery with LiNi0.6Co0.2Mn0.2O2 as cathode. This work offers a promising design route of novel metal sulfides nanostructures for high performance LIBs.

Transmission electron microscopy (TEM) is a powerful tool for unveiling the structural, compositional, and electronic properties of organic-inorganic hybrid perovskites (OIHPs) at the atomic to micrometer length scales. However, the structural and compositional instability of OIHPs under electron beam radiation results in misunderstandings of the microscopic structure-property-performance relationship in OIHP devices. Here, ultralow dose TEM is utilized to identify the mechanism of the electron-beam-induced changes in OHIPs and clarify the cumulative electron dose thresholds (critical dose) of different commercially interesting state-of-the-art OIHPs, including methylammonium lead iodide (MAPbI(3)), formamidinium lead iodide (FAPbI(3)), FA(0.83)Cs(0.17)PbI(3), FA(0.15)Cs(0.85)PbI(3), and MAPb(0.5)Sn(0.5)I(3). The critical dose is related to the composition of the OIHPs, with FA(0.15)Cs(0.85)PbI(3) having the highest critical dose of approximate to 84 e angstrom(-2) and FA(0.83)Cs(0.17)PbI(3) having the lowest critical dose of approximate to 4.2 e angstrom(-2). The electron beam irradiation results in the formation of a superstructure with ordered I and FA vacancies along (c), as identified from the three major crystal axes in cubic FAPbI(3), (c), (c), and (c). The intragrain planar defects in FAPbI(3) are stable, while an obvious modification is observed in FA(0.83)Cs(0.17)PbI(3) under continuous electron beam exposure. This information can serve as a guide for ensuring a reliable understanding of the microstructure of OIHP optoelectronic devices by TEM.

Developing host materials with high specific surface area, good electron conductivity, and fast ion transportation channel is critical for high performance lithium-selenium (Li-Se) batteries. Herein, a series of three dimensional ordered hierarchically porous carbon (3D OHPC) materials with micro/meso/macropores are designed and synthesized for Li-Se battery. The porous structure is tuned by following the concept of the generalized Murray's law to facilitate the mass diffusion and reduce ion transport resistance. The optimized 3D Se/OHPC cathode exhibits a very high 2nd discharge capacity of 651 mAh/g and retains 361 mAh/g after 200 cycles at 0.2 C. Even at a high current rate of 5 C, the battery still shows a discharge capacity as high as 155 mAh/g. The improved electrochemical performance is attributed to the synergy effect of the interconnected and well-designed micro, meso and macroporosity while shortened ions diffusion pathways of such Murray materials accelerate its ionic and electronic conductivities leading to the enhanced electrochemical reaction. The diffusivity coefficient in Se/OHPC can reach a very high value of 1.3 × 10−11 cm2/s, much higher than those in single pore size carbon hosts. Their effective volume expansion accommodation capability and reduced dissolution of polyselenides ensure the high stability of the battery. This work, for the first time, established the clear relationship between textural properties of cathode materials and their performance and demonstrates that the concept of the generalized Murray's law can be used as efficient guidance for the rational design and synthesis of advanced hierarchically porous materials and the great potential of 3D OHPC materials as a practical high performance cathode material for Li-Se batteries.

ABSTACT In-plane anisotropy (IPA) due to asymmetry in lattice structures provides an additional parameter for the precise tuning of characteristic polarization-dependent properties in two-dimensional (2D) materials, but the narrow range within which such method can modulate properties hinders significant development of related devices. Herein we present a novel periodic phase engineering strategy that can remarkably enhance the intrinsic IPA obtainable from minor variations in asymmetric structures. By introducing alternant monoclinic and rutile phases in 2D VO2 single crystals through the regulation of interfacial thermal strain, the IPA in electrical conductivity can be reversibly modulated in a range spanning two orders of magnitude, reaching an unprecedented IPA of 113. Such an intriguing local phase engineering in 2D materials can be well depicted and predicted by a theoretical model consisting of phase transformation, thermal expansion, and friction force at the interface, creating a framework applicable to other 2D materials. Ultimately, the considerable adjustability and reversibility of the presented strategy provide opportunities for future polarization-dependent photoelectric and optoelectronic devices.

Recently, Se cathodes have caught growing attention owing to their higher electronic conductivity, better compatibility with the carbonate electrolyte and comparable theoretical volumetric capacity to S cathodes. However, large volume variation, shuttle effect and sluggish redox kinetics have hindered the development of Li-Se batteries. Herein, we report chain-mail Co@C nanoparticles (Co@C NPs) embedded in macro-meso-microporous carbon nanofibers (CPCFs) with the characteristics of generalized Murray's law as a flexible Se host for advanced Li-Se batteries. The chain-mail Co@C structure protects Co from both active species and electrolyte, and then strengthens the adsorption-catalytic functions for active Se and Li2Se, thus improving the one-step solid-phase redox. In addition, the hierarchical porous structure enhances mass transfer and relieves volume expansion. Accordingly, the Se@CPCFs cathode demonstrates a high capacity of ∼500 mA h g−1 at 0.2C (1C = 675 mA g−1) after 500 cycles and exhibits high-capacity retention of 97.4%, 97.6%, and 99.1% between 1 and 100, 100 and 300, and 300 and 500 cycles. An excellent rate capability at 10C with a reversible specific capacity of 438 mA h g−1 is also realized. This work pioneered the utilization of chain-mail metal NPs as electrocatalysts to accelerate the solid-phase redox kinetics of Se cathodes for advanced Li-Se batteries.

An electric-field induced phase transition between semiconducting 2H and metallic 1T′ phases in a MoTe2 device is demonstrated for the first time. The phase transition exhibits faster switching compared with phase-change random-access memory (PCRAM), and shows more controllable switching than conventional memristive devices.

Lignocellulosic biomass photoreforming is a promising and alternative strategy for both sustainable H2 production and biomass valorization with infinite solar energy. However, harsh reaction conditions (high alkalinity or toxic organic solvents), with low biomass conversion and selectivity are often reported in literature. In this work, we report glucose photoreforming for coproduction of H2 and arabinose with improved selectivity under neutral condition using carbon quantum dots (CQDs) modified TiO2 composites. We show that the conventional CQDs fabricated by a facile one-step hydrothermal process could be endowed with novel color changing property, due to the particle aggregation under the regulation of incident light. The as-fabricated CQDs/TiO2 composites with certain colored CQDs could greatly improve glucose to arabinose conversion selectivity (~75%) together with efficient hydrogen evolution (up to 2.43 mmolh−1g−1) in water. The arabinose is produced via the direct C1-C2 α-scissions mechanism with reactive oxygen species of O2− and OH, as evidenced by 13C labeled glucose and the electron spin-resonance (ESR) studies, respectively. This work not only sheds new lights on CQDs assisted photobiorefinery for biomass valorization and H2 coproduction, but also opens the door for rationale design of different colored CQDs and their potential applications for solar energy utilization in the noble-metal-free system.

Sodium-selenium (Na-Se) batteries have been widely regarded as promising large-scale energy storage systems owing to the high volumetric energy density of 2530 W h L−1 and natural abundance of the element sodium. However, critical drawbacks including sluggish redox kinetics, severe volume variation and shuttle effect seriously deteriorate the electrochemical performance. Herein, we propose a precompetitive coordination strategy for over-coordinated single-atom catalyst, and subsequently synthesize the six-coordinated Co electrocatalyst supported carbon nanofibers (Co-N4C2) for solid-state conversion in wide-temperature Na-Se batteries. The Co-N4C2 catalyst can not only boost the redox kinetics of solid-phase Na2Se2/Na2Se, but also accelerate the electroreduction of ethylene carbonate to construct robust cathode electrolyte interphase, thereby inhibiting the irreversible phase transformation of active Se species. Furthermore, for the first time, the components of the cathode electrolyte interphase as sodium ethylene mono-carbonate are identified. Consequently, the as-synthesized free-standing Se@Co-N4C2 cathode with high Se-loading realizes high capacity, cycling stability and rate capability at both room temperature (20.0/40.0 ℃) and low temperature (− 11.7 ℃).

Lithium-selenium batteries (LSeBs) have attracted increasing attention due to their excellent electronic conductivity and high theoretical specific capacity. However, there are still difficult problems such as low utilization rate and fast capacity decay in the actual application process. Herein, a surface iodine modified three-dimensional (3D) nano hollow carbon fiber (I-NHCF) network is designed and synthesized as Se host (Se@I-NHCF) for highly stable LSeBs. The surface iodine species induce the formation of robust cathode electrolyte interface (CEI), thus preventing the transformation of amorphous selenium to low-activity crystalline selenium and enabling stable electrochemical performance. Moreover, the surface iodine species promote rapid charge transfer, enhancing the chemical reaction kinetics and improving the utilization of the active Se species. As a result, the Se@I-NHCF cathode exhibits superior specific capacity of 581.8 mAh g−1 with a high stability (0.0054% capacity decay per cycle) after 500 cycles at 1C, and an excellent rate performance of 567.6 mAh g−1 at 2C. This work addresses the problem of rapid capacity decay by the formation of uniform and robust CEI to conserve highly reactive amorphous Se species, improve Se utilization, and achieve ultra-stable Li-Se batteries with high energy and long cycle life.

Uncovering an efficient and stable photocatalytic system for seawater splitting is a highly desirable but challenging goal. Herein, Cd0.2Zn0.8S@Silicalite-1 (CZS@S-1) composites, in which CZS is embedded in the hierarchical zeolite S-1, were prepared and show remarkably high activity, stability and salt resistance in seawater.

Uronic acid in extracellular polymeric substances is a primary but often ignored factor related to the difficult hydrolysis of waste-activated sludge (WAS), with alginate as a typical polymer. Previously, we enriched alginate-degrading consortia (ADC) in batch reactors that can enhance methane production from WAS, but the enzymes and metabolic pathway are not well documented. In this work, two chemostats in series were operated to enrich ADC, in which 10 g/L alginate was wholly consumed. Based on it, the extracellular alginate lyase (∼130 kD, EC 4.2.2.3) in the cultures was identified by metaproteomic analysis. This enzyme offers a high specificity to convert alginate to disaccharides over other mentioned hydrolases. Genus Bacteroides (>60%) was revealed as the key bacterium for alginate conversion. A new Entner−Doudoroff pathway of alginate via 5-dehydro-4-deoxy-D-glucuronate (DDG) and 3-deoxy-D-glycerol-2,5-hexdiulosonate (DGH) as the intermediates to 2-keto-3-deoxy-gluconate (KDG) was constructed based on the metagenomic and metaproteomic analysis. In summary, this work documented the core enzymes and metabolic pathway for alginate degradation, which provides a good paradigm when analyzing the degrading mechanism of unacquainted substrates. The outcome will further contribute to the application of Bacteroides-dominated ADC on WAS methanogenesis in the future.

Diffusion is an extremely critical step in zeolite catalysis that determines the catalytic performance, in particular for the conversion of bulky molecules. Introducing interconnected mesopores and macropores into a single microporous zeolite with the rationalized pore size at each level is an effective strategy to suppress the diffusion limitations, but remains highly challenging due to the lack of rational design principles. Herein, we demonstrate the first example of boosting molecular diffusion by constructing hierarchical Murray zeolites with a highly ordered and fully interconnected macro–meso–microporous structure on the basis of the generalized Murray's Law. Such a hierarchical Murray zeolite with a refined quantitative relationship between the pore size at each length scale exhibited 9 and 5 times higher effective diffusion rates, leading to 2.5 and 1.5 times higher catalytic performance in the bulky 1,3,5-triisopropylbenzene cracking reaction than those of microporous ZSM-5 and ZSM-5 nanocrystals, respectively. The concept of hierarchical Murray zeolites with optimized structural features and their design principles could be applied to other catalytic reactions for maximized performance.

Lithium-selenium (Li-Se) batteries have recently attracted increasingly attentions due to the high electronic conductivity and volumetric capacity of Se. However, the low selenium utilization and inferior electrode kinetics hamper the practical application of Li-Se batteries. In this work, a MoSe2@CNT/GO hybrid interlayer modified polypropylene (PP) (MoSe2@CNT/GO-PP) separator is designed to realize high-performance Li-Se batteries. The MoSe2@CNT/GO interlayer not only facilitates fast kinetic process by catalyzing the conversion of Li2Se, but also has strong chemisorption of Li2Se. These largely improve the selenium utilization. As a result, the Li-Se batteries with MoSe2@CNT/GO-PP separators exhibit a high reversible capacity of 547.2 mAh g−1 after 300 cycles at 0.5C and an excellent rate capability of 390.2 mAh g−1 at 5C. This work provides a new insight for enhancing the electrochemical performance of Li-Se batteries via modifying the separator.

Supercapacitor-like Na-ion batteries have attracted much attention due to the high energy density of batteries and power density of capacitors. Titanium dioxide (TiO2), is a promising anode material. Its performance is however seriously hindered by its low electrical conductivity and the sluggish diffusion of sodium ions (Na+) in the TiO2 matrix. Herein, this work combines porous TiO2 nanocubes with carbon nanotubes (CNTs) to enhance the electrical conductivity and accelerate Na+ diffusivity for Na-ion batteries (NIBs). In this composite, an interwoven scaffolded TiO2/CNTs framework is formed to provide abundant channels and shorter diffusion pathways for electrons and ions. The in-situ X-ray diffraction and cyclic voltammetry confirm the low strain and superior transport kinetics in Na+ intercalation/extraction processes. In addition, the chemically bonded TiO2/CNTs hybrid provides a more feasible channel for Na+ insertion/extraction with a much lower energy barrier. Consequently, the TiO2/CNTs composite exhibits excellent electrochemical performance with a capacity of 223.4 mAh g−1 at 1 C and a capacity of 142.8 mAh g−1 at 10 C (3.35 A g−1). The work here reveals that the combination of active materials with CNTs can largely improve the utilization efficiency and enhance their sodium storage.

Lithium–selenium (Li–Se) battery has attracted growing attention. Nevertheless, its practical application is still impeded by the shuttle effect of the formed polyselenides. Herein, we report in-situ hydrothermal weaving the three-dimensional (3D) highly conductive hierarchically interconnected nanoporous web by threading microporous metal organic framework MIL-68(Al) crystals onto multi-walled carbon nanotubes (MWCNTs). Such 3D hierarchically nanoporous web (3D MIL-68 (Al)@MWCNTs web) with a very high surface area, a large amount of micropores, electrical conductivity and elasticity strongly traps the soluble polyselenides during the electrochemical reaction and significantly facilitates lithium ion diffusion and electron transportation. Molecular dynamic calculation confirmed the strong affinity of MIL-68 (Al) for the adsorption of polyselenides, quite suitable for Li–Se battery. Their hexahedral channels (1.56 nm) are more efficient for the confinement of polyselenides and for the diffusion of electrolytes compared to their smaller triangular channels (0.63 nm). All these excellent characteristics of 3D MIL-68 (Al)@MWCNTs web with suitable confinement of a large amount of selenium and the conductive linkage between MIL-68(Al) host by MWCNTs result in a high capacity of 453 mAh/g at 0.2C with 99.5% coulombic efficiency after 200 cycles with significantly improved cycle stability and rate performance. The 3D MIL-68 (Al)@MWCNTs web presents a good performance in Li–Se battery in term of the specific capacity and cycling stability and also in terms of rate performance compared with all the metal–organic framework (MOF) based or MOF derived porous carbons used in Li–Se battery.

Developing anatase/rutile phase-junction in TiO2 to construct Z-scheme system is quite effective to improve its photoelectrochemical activity. In this work, the anatase/rutile phase-junction Ag/TiO2 nanocomposites are developed as photocathodes for hydrogen production. The optimized Ag/TiO2 nanocomposite achieves a high current density of 1.28 mA cm−2, an incident photon-to-current conversion efficiency (IPCE) of 10.8 %, an applied bias photon-to-current efficiency (ABPE) of 0.32 at 390 nm and a charge carriers’ lifetime up to 2000s. Such enhancement on photoelectrochemical activity can be attributed to: (i) the generated Z-scheme system in the anatase/rutile phase-junction Ag/TiO2 photocathode enhances the separation, diffusion and transformation of electron/hole pairs inside the structure, (ii) Ag nanodots modification in the anatase/rutile phases leading to the tuned band gap with enhanced light absorption and (iii) the formed Schottky barrier after Ag nanodots surface modification provides enough electron traps to avoid the recombination of photogenerated electrons and holes. Our results here suggest that developing phase-junction nanocomposite as photocathode will provide a new vision for their enhanced photoelectrochemical generation of hydrogen.

Lithium-sulfur (Li-S) batteries have attracted significant attention for their high specific capacity, non-toxic and harmless advantages. However, the shuttle effect limits their development. In this work, small-sized tin disulfide (SnS2) nanoparticles are embedded between interlayers of two-dimensional porous carbon nanosheets (PCNs), forming a multi-functional nanocomposite (PCN-SnS2) as a cathode carrier for Li-S batteries. The graphitized carbon nanosheets improve the overall conductivity of the electrode, and the abundant pores not only facilitate ion transfer and electrolyte permeation, but also buffer the volume change during the charge and discharge process to ensure the integrity of the electrode material. More importantly, the physical confinement of PCN, as well as the strong chemical adsorption and catalytic reaction of small SnS2 nanoparticles, synergistically reduce the shuttle effect of polysulfides. The interaction between a porous layered structure and physical-chemical confinement gives the PCN-SnS2-S electrode high electrochemical performance. Even at a high rate of 2 C, a discharge capacity of 650 mA h g−1 is maintained after 150 cycles, underscoring the positive results of SnS2 based materials for Li S batteries. The galvanostatic intermittent titration technique results further confirm that the PCN-SnS2-S electrode has a high Li+ transmission rate, which reduces the activation barrier and improves the electrochemical reaction kinetics. This work provides strong evidence that reducing the size of SnS2 nanostructures is beneficial for capturing and reacting with polysulfides to alleviate their shuttle effect in Li-S batteries.

A deep understanding of the fine structure at the atomic scale of halide perovskite materials has been limited by their sensitivity to the electron beam that is widely used for structural characterization. The sensitivity of a gamma-CsPbIBr2 perovskite thin film under electron beam irradiation is revealed by scanning transmission electron microscopy (STEM) through a universal large-range electron dose measurement, which is based on discrete single-electron events in the STEM mode. Our research indicates that the gamma-CsPbIBr2 thin film undergoes structural changes with increasing electron overall dose (e(-).A(-2)) rather than dose rate (e(-).A(-2).s(-1)), which suggests that overall dose is the key operative parameter. The electron beam-induced structural evolution of gamma-CsPbIBr2 is monitored by fine control of the electron beam dose, together with the analysis of high-resolution (S)TEM, diffraction, and energy-dispersive X-ray spectroscopy. Our results show that the gamma-CsPbIBr2 phase first forms an intermediate phase [e.g., CsPb(1-x)(IBr)((3-y))] with a superstructure of ordered vacancies in the pristine unit cell, while a fraction of Pb2+ is reduced to Pb-0. As the electron dose increases, Pb nanoparticles precipitate, while the remaining framework forms the Cs2IBr phase, accompanied by some amorphization. This work provides guidelines to minimize electron beam irradiation artifacts for atomic-resolution imaging on CsPbIBr2 thin films.

Motility is significant in organisms. Studying the influence of motility on biological processes provides a new angle in understanding the essence of life. Biomineralization is a representative process for organisms in forming functional materials. In the present study, we investigated the biomineralization of iron oxides templated by Escherichia coli (E. coli) cells under oscillation. The formation of iron oxide minerals with acicular and banded morphology was observed. The surface charge of E. coli cells contributed to the biomineralization process. The surface components of E. coli cells including lipids, carbohydrates and proteins also have roles in regulating the formation and morphology of iron oxide minerals. As-prepared mineralized iron oxide nanomaterials showed activity in photocatalytic degradation of methylene blue as well as in electrocatalytic hydrogen evolution reaction. This study is helpful not only in understanding motility in biological processes, but also in developing techniques for fabricating functional nanomaterials.

Hydrogen evolution from biomass photoreforming has been widely recognized as a promising strategy for relieving the pressure from energy crisis and environmental pollution, as it could generate sustainable H2 and value-added bioproducts simultaneously. Combining p-type semiconductors with n-type semiconductors to form n-p heterojunction is an effective strategy to improve the photocatalytic quantum efficiency by enhancing the separation of photogenerated electrons and holes, which could greatly facilitate the realization of such biomass photorefinery concept. However, the incompact contact between the n-type and p-type semiconductors often induces the aggregation of photogenerated electrons and holes. In this work, we design and synthesize an ultrafine n-p heterojunction TiO2-NiO core-shell structure to overcome the incompact contact in the n-p interface. When the n-p heterojunction photocatalysts are evaluated for photocatalytic water splitting and biomass lignin photoreforming respectively, the as-fabricated TiO2-NiO nanocomposite with 3.25% NiO demonstrates the highest hydrogen generation of 23.5 mmol h−1 g−1 from water splitting and H2 (0.45 mmol h−1 g−1) and CH4 (0.03 mmol h−1 g−1) cogeneration with reasonable amount of fatty acids (palmitic acid and stearic acid) production from lignin photoreforming. The excellent photocatalytic activity is ascribed to the synergistic effects of high crystallinity of TiO2 ultrafine nanoparticles, core-shell structure and n-p heterojunction with NiO nanoclusters. This present work demonstrates a simple and efficient method to fabricate ultrafine n-p heterojunction core-shell structure for noble-metal free catalyst for both water splitting and biomass photoreforming.

The introduction of Na+ is considered as an effective way to improve the performance of Ni-rich cathode materials. However, the direct structure–property correlation for Na+ doped NCM-based cathode materials remain unclear, due to the difficulty of local and accurate structural characterization for light elements such as Li and Na. Moreover, there is the complexity of the modeling for the whole Li ion battery (LIB) system. To tackle the above-mentioned issues, we prepared Na+-doped LiNi0.6Co0.2Mn0.2O2 (Na-NCM622) material. The crystal structure change and the lattice distortion with picometers precision of the Na+-doped material is revealed by Cs-corrected scanning transmission electron microscopy (STEM). Density functional theory (DFT) and the recently proposed electrochemical model, i.e., modified Planck-Nernst-Poisson coupled Frumkin-Butler-Volmer (MPNP-FBV), has been applied to reveal correlations between the activation energy and the charge transfer resistance at multiscale. It is shown that Na+ doping can reduce the activation energy barrier from ΔG = 1.10 eV to 1.05 eV, resulting in a reduction of the interfacial resistance from 297 Ω to 134 Ω. Consequently, the Na-NCM622 cathode delivers a superior capacity retention of 90.8 % (159 mAh.g−1) after 100 cycles compared to the pristine NCM622 (67.5 %, 108 mAh. g−1). Our results demonstrate that the kinetics of Li+ diffusion and the electrochemical reaction can be enhanced by Na+ doping the cathode material.

Li-Se battery is a promising energy storage candidate owing to its high theoretical volumetric capacity and safe operating condition. In this work, for the first time, we report using the whole organic Melamine-based porous polymer networks (MPNs) as a precursor to synthesize a N, O, S co-doped hierarchically porous carbon nanobelts (HPCNBs) for both Li-ion and Li-Se battery. The N, O, S co-doping resulting in the defect-rich HPCNBs provides fast transport channels for electrolyte, electrons and ions, but also effectively relieve volume change. When used for Li-ion battery, it exhibits an advanced lithium storage performance with a capacity of 345 mAh g−1 at 500 mA g−1 after 150 cycles and a superior rate capacity of 281 mAh g−1 even at 2000 mA g−1. Further density function theory calculations reveal that the carbon atoms adjacent to the doping sites are electron-rich and more effective to anchor active species in Li-Se battery. With the hierarchically porous channels and the strong dual physical–chemical confinement for Li2Se, the Se@ HPCNBs composite delivers an ultra-stable cycle performance even at 2 C after 1000 cycles. Our work here suggests that introduce of heteroatoms and defects in graphite-like anodes is an effective way to improve the electrochemical performance.

The biomass photorefinery provides a promising strategy for value-added chemical production from natural feedstocks. Herein, we designed and fabricated a three-dimensionally ordered macroporous (3DOM) ternary composite for the photoreforming of hemicellulose and the corresponding monosaccharides. This hierarchically porous structure was revealed to restrain the crystal growth of BiVO4 and ZnO to form nanodots and clusters, respectively. The ternary photocatalyst exhibited excellent xylose conversion (∼90%) to selectively produce formic acid (∼60% selectivity) due to the synergistic effects of light harvesting, mass diffusion, oxygen vacancies and the formed heterojunction structure. The as-fabricated photocatalyst also showed the ability to break down β-1,4-glycosidic linkages of xylan in hemicellulose from wheat straw to produce xylose and formic acid. This work demonstrates a facile pathway for lignocellulose valorization to value-added chemicals by the photorefinery strategy.

MXenes, a new family of functional two-dimensional (2D) materials, have shown great potential for an extensive variety of applications within the last decade. Atomic defects and functional groups in MXenes are known to have a tremendous influence on the functional properties. In this review, we focus on recent progress in the characterization of atomic defects and functional group chemistry in MXenes, and how to control them to directly influence various properties (e.g., electron transport, Li' adsorption, hydrogen evolution reaction (HER) activity, and magnetism) of 2D MXenes materials. Dynamic structural transformations such as oxidation and growth induced by atomic defects in MXenes are also discussed. The review thus provides perspectives on property optimization through atomic defect engineering, and bottom-up synthesis methods based on defect-assisted homoepitaxial growth of MXenes. (C) 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.

Three-dimensionally ordered macroporous (3DOM) structures have been widely utilized to largely enhance a photocatalytic activity. However, the common nanoparticles-constructed 3DOM photocatalysts possess numerous grain boundaries, unavoidably leading to a fast recombination of photogenerated electrons and holes. Herein, for the first time, a hierarchically two-dimensional (2D) meso-microporous perovskite nanosheet-constructed 3DOM CaTiO3 to significantly reduce the grain boundaries is designed and fabricated. Using carbon quantum dots (CQDs) as a metal-free co-catalyst, the 3DOM CQDs-CaTiO3 exhibits an outstanding photocatalytic activity for hydrogen generation of 0.13 mmol h−1 (20 mg photocatalyst) with remarkable apparent quantum efficiency (QAY) of 14.55% at 365 nm monochromatic light. This unprecedented performance is endowed by the synergy of a macro-meso-microporosity architecture, a large surface area, enhanced light harvesting, and improved charge carriers separation and transport. Density functional theory calculations and finite difference time-domain simulations further reveal the mechanism behind the enhanced separation of photogenerated electrons and holes. The present work demonstrates a trial on rationally designing meso-microporous nanosheet-constructed 3DOM perovskites for solar driven hydrogen production.

High-entropy alloys (HEAs) contain multiple principal alloying elements, but usually with simple crystal structures. Quasicrystals are structurally complex phases, but are generally dominated by only one element. However, near-equiatomic high-entropy quasicrystals have rarely been reported because they are difficult to prepare experimentally and predict theoretically. Therefore, the preparation and crystal structures of near-equiatomic high-entropy quasicrystals have drawn much interest. We report a quinary decagonal quasicrystal (DQC) with near-equiatomic alloying elements in Al20Si20Mn20Fe20Ga20 melt-spun ribbons, which is the first to our knowledge. Meanwhile, the structural features of the DQC are characterized in detail. The configurational entropy of both the alloy and DQC satisfies the entropy-based criterion for HEAs, suggesting a high-entropy DQC. Our findings provide a new strategy to develop high-entropy quasicrystals.

Zeolite Beta single crystals with intracrystalline hierarchical porosity at macro-, meso-, and micro-length scales can effectively overcome the diffusion limitations in the conversion of bulky molecules. However, the construction of large zeolite Beta single crystals with such porosity is a challenge. We report herein the synthesis of hierarchically ordered macro-mesoporous single-crystalline zeolite Beta (OMMS-Beta) with a rare micron-scale crystal size by an in situ bottom-up confined zeolite crystallization strategy. The fully interconnected intracrystalline macro-meso-microporous hierarchy and the micron-sized single-crystalline nature of OMMS-Beta lead to improved accessibility to active sites and outstanding (hydro)thermal stability. Higher catalytic performances in gas-phase and liquid-phase acid-catalyzed reactions involving bulky molecules are obtained compared to commercial Beta and nanosized Beta zeolites. The strategy has been extended to the synthesis of other zeolitic materials, including ZSM-5, TS-1, and SAPO-34.

Hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios (Hier-ZSM-5-x, where x = 50, 100, 150 and 200) were synthesized using an ordered mesoporous carbon-silica composite as hard template. Hier-ZSM-5-x exhibits improved mass transport properties, excellent mechanical and hydrothermal stability, and higher catalytic activity than commercial bulk zeolites in the benzyl alcohol self-etherification reaction. Results show that a decrease in the Si/Al ratio in hierarchical single-crystal ZSM-5 zeolites leads to a significant increase in the acidity and the density of micropores, which increases the final catalytic conversion. The effect of porous hierarchy on the diffusion of active sites and the final catalytic activity was also studied by comparing the catalytic conversion after selectively designed poisoned acid sites. These poisoned Hier-ZSM-5-x shows much higher catalytic conversion than the poisoned commercial ZSM-5 zeolite, which indicates that the numerous intracrystalline mesopores significantly reduce the diffusion path of the reactant, leading to the faster diffusion inside the zeolite to contact with the acid sites in the micropores predominating in ZSM-5 zeolites. This study can be extended to develop a series of hierarchical single-crystal zeolites with expected catalytic performance.

Single-atom catalysts (SACs) have attracted widespread interest for many catalytic applications because of their distinguishing properties. However, general and scalable synthesis of efficient SACs remains significantly challenging, which limits their applications. Here we report an efficient and universal approach to fabricating a series of high-content metal atoms anchored into hollow nitrogen-doped graphene frameworks (M-N-Grs; M represents Fe, Co, Ni, Cu, etc.) at gram-scale. The highly compatible doped ZnO templates, acting as the dispersants of targeted metal heteroatoms, can react with the incoming gaseous organic ligands to form doped metal–organic framework thin shells, whose composition determines the heteroatom species and contents in M-N-Grs. We achieved over 1.2 atom % (5.85 wt %) metal loading content, superior oxygen reduction activity over commercial Pt/C catalyst, and a very high diffusion-limiting current (6.82 mA cm–2). Both experimental analyses and theoretical calculations reveal the oxygen reduction activity sequence of M-N-Grs. Additionally, the superior performance in Fe-N-Gr is mainly attributed to its unique electron structure, rich exposed active sites, and robust hollow framework. This synthesis strategy will stimulate the rapid development of SACs for diverse energy-related fields., An efficient and universal approach to fabricating a series of high-content metal atoms anchored into hollow nitrogen-doped graphene frameworks is developed via a nicely designed process.