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Electrocatalytic water splitting, as a sustainable, pollution-free and convenient method of hydrogen production, has attracted the attention of researchers. However, due to the high reaction barrier and slow four-electron transfer process, it is necessary to develop and design efficient electrocatalysts to promote electron transfer and improve reaction kinetics. Tungsten oxide-based nanomaterials have received extensive attention due to their great potential in energy-related and environmental catalysis. To maximize the catalytic efficiency of catalysts in practical applications, it is essential to further understand the structure–property relationship of tungsten oxide-based nanomaterials by controlling the surface/interface structure. In this review, recent methods to enhance the catalytic activities of tungsten oxide-based nanomaterials are reviewed, which are classified into four strategies: morphology regulation, phase control, defect engineering, and heterostructure construction. The structure–property relationship of tungsten oxide-based nanomaterials affected by various strategies is discussed with examples. Finally, the development prospects and challenges in tungsten oxide-based nanomaterials are discussed in the conclusion. We believe that this review provides guidance for researchers to develop more promising electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

Li et al. [[3]] fabricated a CoFe SB 2 sb O SB 4 sb /g-C SB 3 sb N SB 4 sb composite catalyst with CoFe SB 2 sb O SB 4 sb particles supported on the flaky g-C SB 3 sb N SB 4 sb using a scalable facile method. However, currently, Li-S batteries suffer from low volumetric energy density and poor cycling stability due to the intrinsic low conductivity of sulfur and its discharge product, lithium polysulfide shuttle effect, and so on. Developing efficient and low-cost energy conversion and storage devices and technologies is all-important issue in order to achieve a low-carbon society, whose performance essentially depends on the properties of materials. Zhao et al. [[8]] designed a single-atom catalyst Au/WSSe by filling the single Au atom at the S vacancy site in the Janus WSSe monolayer. [Extracted from the article]

Atomically thin two-dimensional transition metal dichalcogenides (TMDCs) have been regarded as ideal and promising nanomaterials that bring broad application prospects in extensive fields due to their ultrathin layered structure, unique electronic band structure, and multiple spatial phase configurations. TMDCs with different phase structures exhibit great diversities in physical and chemical properties. By regulating the phase structure, their properties would be modified to broaden the application fields. In this mini review, focusing on the most widely concerned molybdenum dichalcogenides (MoX2: X = S, Se, Te), we summarized their phase structures and corresponding electronic properties. Particularly, the mechanisms of phase transformation are explained, and the common methods of phase regulation or phase stabilization strategies are systematically reviewed and discussed. We hope the review could provide guidance for the phase regulation of molybdenum dichalcogenides nanomaterials, and further promote their real industrial applications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) layered materials are assembled through the intralayer covalent bonds and interlayer van der Waals (vdWs) interactions. The relatively weak interlayer vdWs interactions result in the weak interlayer mechanical coupling between layers, which strongly impacts the overall mechanical properties of multilayer 2D materials or heterostructures. Experimentally probing the interlayer mechanical coupling is of vital importance on the accumulation of fundamental parameters for their applications in flexible and stretchable devices, yet there are hardly comprehensive reviews in this research field. In this review, we firstly introduce the probing methods of interlayer mechanical coupling, including high-frequency and ultralow-frequency Raman characterizations, nanoindentation of multilayer 2D materials or heterostructures, surface indentation, pressurized blister test, characterization of spontaneously formed nanoblisters, and nano-friction tests. Based on the analysis and comparison of the existing methods and results, we also discuss the advantages and limitations of each method. Finally, the challenges and opportunities in this promising field are discussed. This review summarizes the recent progress in the probing of interlayer mechanical coupling of 2D layered materials and will provide important reference for the rational design of flexible and stretchable devices. [Display omitted] • The interlayer interactions strongly impact the mechanical properties of multilayer 2D materials or heterostructures. • Probing the interlayer mechanical coupling of 2D materials is very important for the accumulation of fundamental parameters. • The current experimental methods of probing the interlayer mechanical coupling of 2D layered materials are summarized. [ABSTRACT FROM AUTHOR]

We introduce a “solution‐processing‐transformation” strategy, deploying solvent vapor as scaffolds, to fabricate high‐quality hydrogen‐bonded organic framework (HOF) membranes. This strategy can overcome the mismatch in processing conditions and crystal growth thermodynamics faced during the facile solution processing of the membrane. The procedure includes the vapor‐trigged in situ transformation of dense amorphous supramolecules to crystalline HOF‐16, with HOF‐11 as the transient state. The mechanism involves a vapor‐activated dissolution‐precipitation equilibrium shifting and hydrogen bonding‐guided molecule rearrangement, elucidated through combined experimental and theoretical analysis. Upon removal of the molecular scaffolds, the resulting HOF‐16 membranes showcase significant improvement in hydrogen separation performance over their amorphous counterparts and previously reported HOF membranes. The method's broad applicability is evidenced by successfully extending it to other substrates and HOF structures. This study provides a fundamental understanding of guest‐induced ordered supramolecular assembly and paves the way for the advanced manufacture of high‐performance HOF membranes for gas separation processes. [ABSTRACT FROM AUTHOR]

Interface strain significantly affects the band structure and electronic states of metal‐nanocrystal‐2D‐semiconductor heterostructures, impacting system performance. While transmission electron microscopy (TEM) is a powerful tool for studying interface strain, its accuracy may be compromised by sample overlap in high‐resolution images due to the unique nature of the metal‐nanocrystals‐2D‐semiconductors heterostructure. Utilizing digital dark‐field technology, the substrate influence on metal atomic column contrasts is eliminated, improving the accuracy of quantitative analysis in high‐resolution TEM images. Applying this method to investigate Pt on MoS2 surfaces reveals that the heterostructure introduces a tensile strain of ≈3% in Pt nanocrystal. The x‐directional linear strain in Pt nanocrystals has a periodic distribution that matches the semi‐coherent interface between Pt nanocrystals and MoS2, while the remaining strain components localize mainly on edge atomic steps. These results demonstrate an accurate and efficient method for studying interface strain and provide a theoretical foundation for precise heterostructure fabrication. [ABSTRACT FROM AUTHOR]

MXenes, a family of 2D transition metal carbides, are considered promising high‐rate pseudocapacitive materials because of their metallic‐like conductivity and transition metal oxide‐like surfaces. Currently, nearly 50 stoichiometric MXenes have been synthesized. However, only a few MXenes, such as Ti3C2, have shown stable pseudocapacitive charge storage so far. Further improving the inherent pseudocapacitance of MXenes without losing their cyclability remains a challenge. Herein, a mild method is reported to produce highly stable bimetallic solid‐solution MXene Ti2VC2 using a solution of potassium fluoride and hydrochloric acid. The electrochemical properties of resulting multilayered clay‐like and delaminated Ti2VC2 films are investigated, exceeding the performance of typical Ti3C2 in acidic electrolytes. These electrodes deliver up to 2000 F cm−3 and retain more than 90% of their initial capacitance after 20 000 cycles, surpassing most state‐of‐the‐art supercapacitor materials known. The pseudocapacitive charge storage of Ti2VC2 is deeply investigated through in situ and ex situ experimental studies, confirmed the pseudocapacitive mechanism is a combination of hydrated H+ intercalation and surface redox. This work provides a practical route toward future rational design on the atomic scale for high‐performance pseudocapacitive materials. [ABSTRACT FROM AUTHOR]

The construction of interfacial electric field (IEF) in semiconductor heterojunction is of great significance in boosting photocatalytic hydrogen evolution through efficient separation of photogenerated charge‐carriers. However, the exploitation of IEF in type‐I heterojunction has not been proposed for designing photocatalysts. Herein, based on the density functional theory prediction, p‐SnS with different work functions modulated by Sn‐vacancy are compounded with n‐ZnIn2S4 containing S‐vacancy to form type‐I heterojunction. The optimized SnS/ZnIn2S4 photocatalyst without co‐catalysts exhibits an impressive hydrogen evolution rate of 22.75 mmol g−1 h−1, 6.23 times of ZnIn2S4. Systematic investigations reveal that the interfacial Sn‐S bond acts as a transport channel that accelerates the interface charge‐carriers transfer under the promotion of IEF originating from the significant Fermi level difference. A large difference in the surface photovoltage signal of SnS/ZnIn2S4 and ZnIn2S4 is achieved from effective photogenerated charge‐carriers separation by IEF. The new p‐n type‐I scheme of SnS/ZnIn2S4 induced by the interfacial mediation can separate the photogenerated charge‐carriers, and retain the highly reductive electrons of ZnIn2S4 for hydrogen evolution, overcoming the disadvantage of reduction potential decline in the typical type‐I scheme. This study will afford a new theoretical basis for the achievement of high‐efficiency photocatalytic hydrogen evolution through interface modulation. [ABSTRACT FROM AUTHOR]

Nanoclusters involve finite metal atoms are of great importance in chemical synthesis and catalysis due to their unique structure-dependent properties. Knowing how nanoclusters work in reaction conditions is no doubt one of the most important challenges, which requires deep insight into atomic-scale dynamics during the process. State-of-the-art in-situ transmission electron microscope (TEM) can realize the real-time study, which is expected to reveal insights into the underlying mechanisms of catalysis and design efficient catalysts. In this minireview, we aim to give a critical review and recent progress on nanocluster dynamics unveiled by in-situ and environmental TEM from two aspects: evolutions of metal single atoms and nanoclusters in high-temperature reaction conditions and the well-defined molecular clusters in confined space. We emphasize the cluster-environment interaction and the cluster structure–property relationships. In the end, we also summarize the present achievements and propose future challenges. We expect this review will fuel the excitement and stimulate research in the fields of cluster and catalysis. [ABSTRACT FROM AUTHOR]

The long–term stability of proton conductors is one of the most important factors in evaluating materials. Guest molecules can act as "bridges" for proton conduction channels and reside in the channels of covalent organic frameworks, but they are prone to leakage. Therefore, it is important to develop proton conductors with intrinsic proton conductivity. In this paper, we synthesized an intrinsically sulfonated covalent organic framework, TpPa–SO3H, which has a more stable proton conducting performance than that of TpPa@H2SO4 by loading guest molecules. Meanwhile, the proton conductivity of TpPa–SO3H was further improved by coating a superabsorbent polymer through an in situ reaction to obtain PANa@TpPa–SO3H (PANa: sodium polyacrylate). As a result, the modified composite exhibits an ultrahigh proton conductivity of 2.33 × 10−1 S cm−1 at 80 °C under 95% relative humidity (RH). The stability of PANa@TpPa–SO3H makes it an efficient proton transport platform with excellent proton conductivity and long–term durability. [ABSTRACT FROM AUTHOR]

Interfacial atomic configuration plays a vital role in the structural stability and functionality of nanocomposites composed of metal nanoparticles (NPs) and two−dimensional semiconductors. In situ transmission electron microscope (TEM) provides a real−time technique to observe the interface structure at atomic resolution. Herein, we loaded bimetallic NiPt truncated octahedral NPs (TONPs) on MoS2 nanosheets and constructed a NiPt TONPs/MoS2 heterostructure. The interfacial structure evolution of NiPt TONPs on MoS2 was in situ investigated using aberration−corrected TEM. It was observed that some NiPt TONPs exhibited lattice matching with MoS2 and displayed remarkable stability under electron beam irradiation. Intriguingly, the rotation of an individual NiPt TONP can be triggered by the electron beam to match the MoS2 lattice underneath. Furthermore, the coalescence kinetics of NiPt TONPs can be quantitatively described by the relationship between neck radius (r) and time (t), expressed as rn = Kt. Our work offers a detailed analysis of the lattice alignment relationship of NiPt TONPs on MoS2, which may enlighten the design and preparation of stable bimetallic metal NPs/MoS2 heterostructures. [ABSTRACT FROM AUTHOR]

Constructing a heterogeneous interface using different components is one of the effective measures to achieve the bifunctionality of nanocatalysts, while synergistic interactions between multiple interfaces can further optimize the performance of single-interface nanocatalysts. The non-precious metal nanocatalysts MoS2/NiSe2/reduced graphene oxide (rGO) bilayer sandwich-like nanostructure with multiple well-defined interfaces is prepared by a simple hydrothermal method. MoS2 and rGO are layered nanostructures with clear boundaries, and the NiSe2 nanoparticles with uniform size are sandwiched between both layered nanostructures. This multiple-interfaced sandwich-like nanostructure is prominent in catalytic water splitting with low overpotential for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and almost no degradation in performance after a 20 h long-term reaction. In order to simulate the actual overall water splitting process, the prepared nanostructures are assembled into MoS2/NiSe2/rGO||MoS2/NiSe2/rGO modified two-electrode system, whose overpotential is only 1.52 mV, even exceeded that of noble metal nanocatalyst (Pt/C||RuO2~1.63 mV). This work provides a feasible idea for constructing multi-interface bifunctional electrocatalysts using nanoparticle-doped bilayer-like nanostructures. [ABSTRACT FROM AUTHOR]

As a typical planar 4-connected ligand that possesses D4h symmetry, the squarate ligand is expected to construct some interesting topologies. Here, we report that the assembly of the squarate ligand with rare-earth ions can produce a series of (4, 8)-connected frameworks with the "smallest" scu type topology. Among these compounds, the Tb based analogue not only possesses a good proton conductivity, but also exhibits luminescence responses toward MnO4− and Cr2O72−, making it a candidate for multifunctional materials. [ABSTRACT FROM AUTHOR]

Cu 2 O is an ideal template material for the preparation of transition metal hydroxide/oxyhydroxides with oxygen evolution reaction (OER) enhanced catalytic performance. Here, inspired by Pearson's principle, Cu 2 O wires were prepared and used as a sacrificial template to prepare Ni(OH) 2 ·0.75H 2 O hollow tubes (Ni(OH) 2 HTs) with highly improved surface roughness. Benefiting from unique structural advantages, the Ni(OH) 2 HTs showed excellent catalytic activity, rapid kinetics and a long-term stability as the OER catalyst, where an overpotential of only 207 ​mV was required to drive a current density of 10 ​mA ​cm−2, an ideal kinetics with a Tafel slope as 79.8 ​mV dec−1 was calculated, and no obvious attenuation in chronoamperometry was discovered after operation for 24 ​h. This paper provides a novel template-assisted strategy to prepare high-performance transition metal-based OER catalysts possessing hollow and tubular structures. [Display omitted] • For the first time , we used Cu 2 O wires as hard template to prepare hollow tubular Ni(OH) 2. • The Ni(OH) 2 HTs possess novel morphologies with stable hollow one-dimensional structure and rough surface. • As OER catalyst, the Ni(OH) 2 HTs showed excellent electrochemical performances for overpotential, kinetics and stability. [ABSTRACT FROM AUTHOR]

Understanding the mechanism of nucleation and growth of nanocrystals is crucial for designing and regulating the structure and properties of nanocrystals. However, the process from molecules to nanocrystals remains unclear because of the rapid and complicated dynamics of evolution under reaction conditions. Here, the complete evolution process of solid‐phase chloroplatinic acid during the electron beam irradiation triggered reduction and nucleation of platinum nanocrystals is recorded. Aberration‐corrected environmental transmission electron microscopy is used for direct visualization of the dynamic evolution from H2PtCl6 to Pt nanocrystals at the atomic scale, including the formation and growth of amorphous clusters, crystallization, and growth of clusters, and the ripening of Pt nanocrystals. At the first two stages, there exists a critical size of ≈2.0 nm, which represents the start of crystallization. Crystallization from the center and density fluctuation are observed in the second stage of the crystallization of a few clusters with a size obviously larger than the critical size. The work provides valuable information to understand the kinetics of the early stage of nanocrystal nucleation and crystallization at atomic scale. [ABSTRACT FROM AUTHOR]

Efficient and durable catalysts are crucial for the oxygen evolution reaction (OER). The discovery of the high OER catalytic activity in Ni12P5 has attracted a great deal of attention recently. Herein, the microscopic mechanism of OER on the surface of Ni12P5 is studied using density functional theory calculations (DFT) and ab initio molecular dynamics simulation (AIMD). Our results demonstrate that the H2O molecule is preferentially adsorbed on the P atom instead of on the Ni atom, indicating that the nonmetallic P atom is the active site of the OER reaction. AIMD simulations show that the dissociation of H from the H2O molecule takes place in steps; the hydrogen bond changes from Oa-H⋯Ob to Oa⋯H-Ob, then the hydrogen bond breaks and an H+ is dissociated. In the OER reaction on nickel phosphides, the rate-determining step is the formation of the OOH group and the overpotential of Ni12P5 is the lowest, thus showing enhanced catalytic activity over other nickel phosphides. Moreover, we found that the charge of Ni and P sites has a linear relationship with the adsorption energy of OH and O, which can be utilized to optimize the OER catalyst. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) materials exhibit unique electronic, optical, magnetic, mechanical, and thermal properties due to their special crystal structure and thus have promising potential in many fields, such as in electronics and optoelectronics. To realize their real applications, especially in integrated devices, the growth of large‐size single crystal is a prerequisite. Up to now, the most feasible way to achieve 2D single crystal growth is the epitaxy: growth of 2D materials of one or more specific orientations with single‐crystal substrate. Only when the 2D domains have the same orientation, they can stitch together seamlessly and single‐crystal 2D films can be obtained. In this view, four different epitaxy modes of 2D materials on various substrates are presented, including van der Waals epitaxy, edge epitaxy, step‐guided epitaxy, and in‐plane epitaxy focusing on the growth of graphene, hexagonal boron nitride (h‐BN), and transition metal dichalcogenide (TMDC). The lattice symmetry relation and the interaction between 2D materials and the substrate are the key factors determining the epitaxy behaviors and thus are systematically discussed. Finally, the opportunities and challenges about the epitaxy of 2D single crystals in the future are summarized. [ABSTRACT FROM AUTHOR]

It is a challenge to effectively load proton carriers in COFs to improve their proton conductivity. Herein, we report a series of COF-based composites, PANa@UCOF-x (PANa: sodium polyacrylate, x: weight percentage of PANa), which were prepared by coating different proportions of superabsorbent PANa on the COF surface based on an in situ reaction strategy. Since PANa can greatly enhance the enrichment of water molecules in one-dimensional (1D) channels of COFs, these COF-based composites exhibit superprotonic conduction. At 80 °C and 95% relative humidity (RH), the proton conductivity of PANa@UCOF-10, PANa@UCOF-28 and PANa@UCOF-40 reaches 1.6 × 10−2, 5.1 × 10−2, and 1.1 × 10−1 S cm−1, respectively, which is 4–5 orders of magnitude higher than 7.4 × 10−7 S cm−1 of the original UCOF. This work not only develops a new method to improve the water content of the COF channels, but also proves the important role of ordered channels in constructing effective proton conduction pathways. [ABSTRACT FROM AUTHOR]

A dual-mode DNA sensor was constructed to detect nucleic acid sensitively and selectively. Based on dendritic porous silica nanoparticles (DPSNs) and hybridization chain reaction (HCR) amplification strategy, the fabricated DNA sensor showed good sensitivity with low detection limits down to 2.18 pM and 4.02 pM by fluorescence (excited at 488 nm and emitted at 508 nm) and personal glucose meter (PGM) assays, respectively. This dual-mode detection of DNA offered superior reliability and accuracy and could meet the requirements of different testing environments, including laboratory confirmation and portable detection. Moreover, the impact of nanoparticles morphology on detection performance was also discussed. Due to the center-radial pores, DPSNs had high curvature morphology, which improved the coverage capacity, footprint, and deflection angle of probes. This work fabricated a dual-mode DNA sensor and revealed the relationship between morphology and detection performance, which brought new insights in novel biosensor development. [ABSTRACT FROM AUTHOR]

Designing low-cost, highly efficient, and stable electrocatalysts for oxygen evolution reactions is of great significance for water splitting, which is a green and sustainable method of producing hydrogen. Herein, a series of transition metal sulphide-based nanostructures, including Au–CoNi2S4 core–shell, Au–NiS core–shell, Au–Co3S4 core–shell, and bare CoNi2S4 nanoparticles (NPs), have been rationally designed. Among them, the Au–CoNi2S4 core–shell NPs exhibit superior electrocatalytic properties for oxygen evolution. It requires an overpotential of only 264 mV to reach a current density of 10 mA cm−2, while the Tafel slope (35.6 mV dec−1) is also the lowest among the as-prepared nanostructures. X-ray photoelectron spectra and electrochemical impedance spectra demonstrate that the electronic structure and chemical state of Au–CoNi2S4 core–shell heterostructure are regulated by the delicate structural design. The enhanced electrocatalytic performance of the Au–CoNi2S4 core–shell heterostructure can be attributed to the combined effects of constructing bimetallic sulphide instead of its monometallic counterparts and forming metal–sulphide core–shell interface. It provides a way to develop a superior electrocatalyst by constructing a metal–bimetallic sulphide core–shell heterostructure. [ABSTRACT FROM AUTHOR]

By direct introducing ionic liquid into the interfacial polymerization process of β-CD, the porous monomer based thin-film composite membranes are fabricated for efficient organic solvent nanofiltration with a high ethanol permeance of 57.01 L·m−2·h−1·MPa−1 and an ideal dye rejection rate of 99.98 %. [Display omitted] • IL assists the interfacial polymerization of porous monomers into membranes. • The TFC membranes exhibit high ethanol permeance and ideal dye rejection. • The effects of IL on the membrane structure and separation property are studied. β-cyclodextrin (β-CD), with intrinsic nano-cavity, is a promising monomer to construct thin-film composite (TFC) membranes for molecular separations. Nevertheless, interfacially polymerize β-CD into continuous membranes is challenging due to the low reactivity of hydroxyl groups. To address this issue, in this work, ionic liquid (IL) has been introduced into the interfacial polymerization (IP) process of β-CD and trimesoyl chloride (TMC), forming high-quality TFC membranes for organic solvent nanofiltration (OSN). Investigations have been done into how IL effects membrane structure and separation performance. In contrast to traditional β-CD-TMC TFC membrane, the β-CD-IL-TMC TFC membrane possesses upgraded crosslinking, continuity, stability, and OSN separation property. The best β-CD-IL-TMC membrane has an ethanol permeance of up to 57.01 L m−2h−1 MPa−1 and Naphthol green B rejection rate of 99.98% and can sustain a stable separation performance within 20-hour test, indicating the fabricated β-CD-IL-TMC membranes have advantage of separating and purifying organic solvent. [ABSTRACT FROM AUTHOR]

Al-MOFs have diverse chemical structures and tunable properties for potential applications in adsorption, separation, catalysis, proton conduction, chirality, and superhydrophobicity fields. [Display omitted] • Systematically summarized the similarities between secondary building units and linkers from the structural aspect of Al-MOFs, the structurally-led approach is distinctive and helps to better understand the crystal chemistry of Al-MOFs. • Introduced the research progress and highlighted several exciting discoveries of studying Al-MOFs. • Demonstrated the development trends, emerging challenges, and opportunities primarily oriented to their scalable production, and aimed at exploring the future application prospects of Al-MOFs from academic research to industrial production. It is essential to explore metal–organic frameworks (MOFs) with high durabilities and versatile properties for practical applications. Multiple metal ions have been utilized to construct MOFs, among which the aluminum ion (Al3+) has drawn intensive attention due to its low toxicity, abundant reserves in the earth, low cost, and sustainability. As an attractive MOF family in virtue of its diverse structures and functions, Al-MOFs exhibit high physicochemical stability and have wide applications in many scientific and engineering fields, due to the diverse secondary building units (SBUs) of Al3+ and the strong Al-O bond. In this review, we systematically summarize the SBUs and linkers from a structural perspective. We also highlight the research progress of Al-MOFs with novel topologies and structures. According to the composition of Al-metal nodes, Al-MOFs can be divided into Al3+-ions, Al3+-chains, or Al3+-clusters. In addition, the potential applications of Al-MOFs in various fields, including adsorption, separation, photocatalysis, electrochemistry, chirality, and superhydrophobicity are discussed. From the perspective of Al-MOF structures, the relationship between the structure and performances of Al-MOFs is reviewed, and the future application prospects of Al-MOFs are discussed. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal carbides and nitrides (MXenes) hold promise as electrode materials for alkali metal ion batteries on account of some fascinating peculiarities. However, the high temperature required in the synthesis of the MAX phase severely hinders its further development. Herein, MAX phase (Ti 2 AlC) is first grown on carbon cloth (CC) by molten salt method at a milder temperature, then the hierarchical structure that Ti 2 C sheets arrayed on the carbon fibers can be obtained after HF treatment, demonstrating 269 mA h g−1 after 400 cycles at 1 mA cm−2 for lithium-ion storage and 206 mA h g−1 after 100 cycles at 0.1 mA cm−2 for sodium-ion storage when served as freestanding anode. Meanwhile, in-situ and ex-situ characterization techniques are employed to monitor the possible phase transitions in the electrochemical process. In addition, the kinetics for carrier diffusion in the electrochemical process is also studied. This work endows edification for configuration of MXene-based freestanding electrode. [Display omitted] • MAX phase would be grown directly on the carbon cloth by molten-salt method. • Neoteric MXene-based freestanding anode can be structured. • The electrode without binder shows distinguished electrochemical performance. [ABSTRACT FROM AUTHOR]

Carbon molecular sieve (CMS) membranes are ideal candidates for natural gas separation due to their rigid pore structures and stability. The chemical composite and spatial configuration of the used precursors for deriving CMS membranes can greatly influence the final microporous structure and separation performance of the membranes. Most CMS membranes are transformed from amorphous precursors such as polymers nowadays. Here, for the first time, we report a new type of CMS membrane derived from a crystalline porous hydrogen-bonded organic framework membrane (named HCMS). The conversion process has been studied with the characterization of TGA, FTIR, XRD, SEM, and pore size distribution. The effect of pyrolysis temperature on the membrane structure has been investigated to achieve optimized CO 2 /CH 4 separation performance. On the one hand, as the pyrolysis temperature increases from 550 to 650 °C, the pore size distribution of HCMS membrane is narrowed, which is conducive to improving the molecular sieving effect of the membrane. On the other hand, higher ratios of graphitic N and pyrrolic N, which show better affinity for CO 2 molecules than pyridinic N, are obtained on the HCMS membranes, leading to more favorable adsorption of CO 2. The optimized HCMS membrane pyrolyzed at 600 °C shows a remarkable CO 2 /CH 4 selectivity of 128 and excellent separation stability at varying temperatures and pressures. The HCMS membranes derived from the crystalline HOF precursor can also maintain a stable separation performance against physical aging. The results reported in this work may open the door to constructing CMS membranes with the precursor of crystalline porous membranes. Crystalline porous hydrogen-bonded organic framework membrane is employed as a new kind of precursor for the first time to derive carbon molecular sieve membrane with a narrow pore size distribution, which reveals good separation selectivity and stability for CO 2 /CH 4. [Display omitted] • For the first time, a HOF membrane is used as a precursor to derive HCMS membrane. • Ordered porosity of HOF leads to a narrow pore size distribution of HCMS membrane. • Effect of pyrolysis temperature on membrane structure and CO 2 affinity is studied. • The HCMS-600 membrane reveals the optimized CO 2 /CH 4 separation selectivity of 128. • The HCMS-600 membrane is long-term stable at variable temperatures and pressures. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ultrasonic synthesis method was reported to construct ZIF-62 for the first time. • The thermal treatment eliminates interfacial voids and increases PIM-1 free volume. • The thermal-treated membranes possess both improved gas permeability and selectivity. • The performance of optimized agZIF-62/PIM-30% MMMs surpassed the 2019 upper bound. • The MMMs can maintain stable performance after H 2 S treatment and a 440-hour test. Porous MOF glasses are candidate fillers for interfacial void mitigation in mixed matrix membranes (MMMs), however, the inevitable decreased porosity in the glassy state is not conducive to membrane performance optimization. The rational design of porous MOF glass based MMMs remains a great challenge to achieve both high permeability and selectivity. Herein, a novel agZIF-62/PIM-1 (agZIF-62 , the glass phase of ZIF-62) membrane has been fabricated by an optimized in-situ thermal treatment of ZIF-62/PIM-1 precursor membranes. Thermal treatment eliminates interfacial non-selective voids between agZIF-62 and PIM-1 , and simultaneously increases PIM-1 free volume. As a consequence, both permeability and selectivity are significantly enhanced. The agZIF-62/PIM-30% membranes exhibit superior and stable separation performances with a CO 2 /CH 4 selectivity of 67 and CO 2 permeability of 5914 Barrer, which are improved by 268% and 27% compared with the pristine PIM-1 membranes, surpassing 2019 upper bound. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is regarded as the efficiency-limiting step because it suffers from a kinetically sluggish four-electron process in water splitting. The intrinsic catalytic activity could be improved by adjusting the electronic structure of the catalyst through interface modification engineering. In this work, Fe ion-chelated tannic acid was coated on Ni-WO x nanowires to form TA-Fe@Ni-WO x hierarchical structure by the interfacial coordination assembly process. The hierarchical structure has abundant active sites and good electrical conductivity, which exhibits extraordinary OER performance in alkaline electrolytes. Specifically, the TA-Fe@Ni-WO x catalyst requires low over-potentials of 240 and 260 mV at 20 mA cm−2 and 50 mA cm−2, respectively. X-ray photoelectron spectroscopy results confirm that the electronic structure of TA-Fe@Ni-WO x is more beneficial to OER than Ni-WO x due to the introduction of the TA-Fe nano-sheets overlayer on the surface of Ni-WO x nanowires. Furthermore, the ultraviolet photoelectron spectroscopy results confirm that the TA-Fe@Ni-WO x hierarchical structure has an upward-moving Fermi energy and a smaller ionization potential, providing a more electron-rich environment. It is demonstrated that this simple interfacial coordination assembly coating strategy is an effective way to reasonably adjust the surface properties of metal oxides for promising applications. • TA-Fe@Ni-WO x hybrids were constructed via an interfacial coordination assembly strategy. • The electronic structure and the electron transfer efficiency of Ni-WO x are effectively regulated by TA-Fe nanosheets. • TA-Fe@Ni-WO x exhibited excellent OER catalytic activities with low over-potential of 240 mV at 20 mA cm−2. [ABSTRACT FROM AUTHOR]

• The self-supported serrated Ni-WO 3 on Ni foam was obtained by one step in-situ etching method. • The NH 4 + and SO 4 2- had synergistic effect on the unique structure. • The serrated Ni-WO 3 exhibits excellent OER activities with low over-potentials of 265 mV at 10 mA cm−2. The effect of etching agent type and reaction time on the morphology and properties of materials was studied in this paper and the reconstruction phenomenon in OER pre-catalyst was confirmed. The serrated Ni-WO 3 -3 has excellent OER performance with an over-potential of only 265 mV at 10 mA cm−2. The serrated Ni-WO 3 electrode undergoes a self-reconstruction of structure and material during OER to form nickel oxy(hydroxide) nanoparticles. [Display omitted] The slow kinetics of oxygen evolution reaction (OER) severely restricts the application of water splitting. In this paper, a free-standing serrated Ni-WO 3 electrode for OER was synthesized by a simple in-situ etching method using (NH 4) 2 SO 4 as etchant. The effect of etchant on structures of Ni-WO 3 were studied carefully, indicating that the NH 4 + and SO 4 2- have a synergistic effect on the unique structure. The serrated Ni-WO 3 -3 (where 3 is the mass of (NH 4) 2 SO 4) dramatically enhance OER performance, an over-potential of only 265 mV at 10 mA cm−2 as compared with that 365 mV of serrated-free Ni-WO 3. Interestingly, the structure and composition of the serrated Ni-WO 3 electrode undergoes a self-reconstruction process during OER, the finally catalyst is interconnected by low crystallinity nickel oxy-hydroxide nanoparticles. This work mainly explores the influence of etching agent type, usage and reaction time on the morphology and properties of materials, and the reconstruction phenomenon in OER pre-catalyst was confirmed. [ABSTRACT FROM AUTHOR]

By the combination of graphene oxide with multiple "plug-ins", the composite membranes are fabricated for nanofiltration with high water permeance (82 L m−2h−1 bar−1) and ideal rejection rate (99.98%). [Display omitted] • The GO membranes contain the multiple "plug-ins" of β-CD and TMC. • The composite membranes exhibit high water permeance and ideal dye rejections. • The different effects of "plug-ins" on the nanofiltration performance are studied. The membranes based on graphene oxide (GO) have shown vast perspectives in nanofiltration, while the swelling of GO membranes in water environment poses a critical challenge for practical applications. In this study, we report the simple fabrication of stable GO membranes in water environment through intercalating multiple "plug-ins": the filter of β-cyclodextrin (β-CD) and the crosslinker of trimesoyl chloride (TMC), which can significantly enhance sieving effect and stability of membranes, and efficiently remove dyes and salts. The β-CD possess the cavity range of 6.0–6.5 Å which is larger than the diameter of water molecules, which can introduce extra water passage and hinder the permeation of dye molecules. In addition, the remaining hydroxyl groups on the membrane surface enhance the hydrophilicity, benefiting to enhance water permeance. At the same time, TMC cross-links β-CD and GO nanosheets to reinforce the membrane. The water permeance of the GO/β-CD/TMC membrane reaches 82 L m−2h−1 bar−1, and the dye rejection (crystal violet) is 99.98%. Therefore, GO membranes prepared by the multiple "plug-ins" incorporation strategy are promising candidates for the nanofiltration process to remove dyes. [ABSTRACT FROM AUTHOR]

[Display omitted] • An exquisite externally layered and internally hollow CoP@MoS 2 electrocatalyst was successfully prepared. • CoP can effectively enhance the catalytic ability of MoS 2 on hydrogen evolution reaction. • The externally layered and internally hollow nanostructure can accelerate the transfer of charge and mass. As the star material among nonprecious electrocatalysts, molybdenum disulfide (MoS 2) has received much attention. However, the catalytic inertness of the basal plane, low conductivity of its steady state (2H phase), and the agglomeration of lamellar structures have seriously hindered its catalytic performance. It is very essential to design and modulate the morphology and phase of MoS 2 to improve the above issues by synergistic regulation of electrical structure and defect engineering. Herein, MoS 2 was delicately composited on CoP nanoframe derived from a typical metal–organic frame nanostructure (ZIF-67), forming the hollow CoP@MoS 2 hetero-nanoframe. This exquisite externally layered and internally hollow CoP@MoS 2 electrocatalyst demonstrated excellent catalytic performance for the hydrogen evolution reaction, with a low overpotential of 119 mV at 10 mA cm−2, a small Tafel slope of 49 mV dec−1, a large electric double-layer capacitance of 10.28 mF cm−2, and prominent long-term stability. The remarkable catalytic performance of hollow CoP@MoS 2 hetero-nanoframe can be attributed to the unique architecture of the hetero-nanostructures, appropriate component ratios, strong interaction between CoP and MoS 2 , and large-scale defects and disorder. First-principles density-functional theory calculations can prove the above arguments adequately, the hydrogen adsorption free energy of CoP@MoS 2 is close to zero. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developing the coordinative unsaturation (Fe-N 2) with nitrogen vacancies. • Nitrogen vacancies and Fe-N 2 active site for boosting electrochemical artificial N 2 fixation. • In situ environmental TEM directly visualize N 2 adsorption on FePcTa-PPy. • Fe-N 2 -opp possesses lower overpotential and excellent dynamics stability for ENRR. The construction of definitive correlation between structure and catalytic properties for electrochemical artificial N 2 fixation is still challenging yet significative. Herein, we have explored the coordinative unsaturation (Fe-N 2) in isolated Fe atoms with nitrogen vacancies (V N, which are located at the opposite coordination sites of the Fe atom) on interconnected carbon for electrocatalytic ammonia synthesis. Benefiting from dual active centers (Fe-N 2 and V N) and the spin density on both of them, the novel catalyst exhibits a synergistic improvement of catalytic activity, selectivity, and stability. This work guides the design of the catalyst theoretically and synergistically and combines the advantages of Fe-N 2 with V N structure creation, defect and spin-state engineering introduction toward the concurrent fulfillment of effective N 2 adsorption and activation. We believe our strategy will incite more investigation into designing high-performance catalysts with well-defined coordinative unsaturation single-atom active sites for ambient ammonia synthesis and other energy conversion system. [ABSTRACT FROM AUTHOR]