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Phosphogypsum (PG)-derived CaSO4·2H2O is employed as a multifunctional protective layer to achieve dendrite-free Zn deposition. This artificial layer provides fast channels for Zn2+ions transportation.

With the development and advancement of healthcare, venous blood collection is becoming an essential tool for the initial screening of patients for disease. In current clinical practice, it is mainly done manually by experienced physicians or nurses. To effectively reduce the repetitive work of healthcare workers, we designed an embedded elbow vein recognition system artificial intelligence technology (AI)-based. Firstly, a prototype of vein vascular identification based on near infrared (NIR) spectroscopy was completed by combining the analysis of vein vascular acquisition data with NIR spectroscopy. Secondly, a deep learning-based image classification algorithm is implemented to classify elbow cover images. Furthermore, we used a CNN-based semantic segmentation algorithm to intelligently extract the region of interest for the veins in the elbow region. Finally, we validated the system in a real environment and achieved high recognition accuracy for elbow veins through effective training and testing strategies.

Sodium metal has shown great potential as an inexpensive anode for rechargeable batteries. However, the growth of sodium dendrites continues to hinder the commercialization of Na metal batteries. Herein, an effective strategy using anion-anchoring halloysite nanotube (HNT) coating was proven to prevent the diffusion of anions and trigger uniform Na deposition. Through theoretical calculation, a model of active site of fixed anions exposed from HNTs after acid activation was established for the first time, revealing that Si–Al sites are effective active site of acid-activated HNTs. Furthermore, HNTs with strong and effective adsorption capacity for anions were obtained by controlling the structure of HNTs to regulate the exposure of Si–Al sites. The strong interaction between sites of acid-activated HNTs and the SO3CF3−anion effectively promotes the dissociation of sodium salts, the release of Na+and subsequent migration. As a result, HNTs acid activation for 4 h shows a steady sodium deposition process and displays high Coulombic efficiency in half cell, long cycle life in symmetric cell and full cell. This work provides a basic theoretical basis for the design of nanoclay with abundant and effective active site to fix anions for dendritic free metal batteries.

In this study, a g-C3N4-Cu2O-TiO2photocatalyst with a novel three-dimensional ordered macroporous (3DOM) structure was successfully prepared using a sacrificial template strategy and a photodeposition method. The influence of the special porous structure with cross pore channels on the photocatalytic properties of the as-prepared sample was studied in detail. Compared with the original photocatalyst (TiO2with 3 wt% Pt), g-C3N4-Cu2O-TiO2exhibited a higher specific surface area and more active sites, thus accelerating the separation efficiency of the photogenerated electron-hole pair. Consequently, the as-prepared photocatalyst showed good photocatalytic performance, reaching a maximum hydrogen production rate of 12,108 µmol g−1h−1and approximately five times higher than that of the pristine comparison sample. The enhanced photoactivity of the g-C3N4-Cu2O-TiO2heterojunction can be ascribed to its double p-n heterojunction and robust porous structure, where the photodeposited Cu2O plays a synergistic catalytic role in the photocatalytic process and the outer clad g-C3N4layer prevents Cu2O oxidation. Additionally, the possible photocatalytic mechanism was briefly discussed based on the experimental results. This work identifies viable pathways for developing low-cost heterojunction photocatalysts with highly efficient photocatalytic activity toward improved solar energy conversion.

A MOF-etching strategy is reported to design hierarchical hollow CoS2–MoS2heteronanosheet arrays. Due to the controllable etching of MOF by MoO42−, the obtained CoS2–MoS2catalyst has abundant heterointerfaces for efficient HER and OER.

The structural design of electrode materials is one of the most important factors that determines the electrochemical performance of energy storage devices. In recent years, hollow micro-/nanoarray structures have been widely explored for energy applications due to their unique structural advantages. Their complex hollow interior and shell arrays enable fast ion diffusion/transport, provide abundant active sites and accommodate volume changes. Moreover, the direct contact of hollow arrays with substrates enhances the mechanical stability during long-term cycling. To date, huge progress has been achieved in the rational design of various hollow array architectures. However, a review on this topic has been rarely reported. Herein, the multifunctional merits and typical synthetic strategies for hollow array structures are analyzed in detail. Furthermore, their applications in electrochemical energy storage (such as supercapacitors and batteries) are summarized. The development and challenges of hollow arrays in terms of substrates, technique improvement and material innovation are discussed. Finally, their applications for energy storage and conversion are prospected.

Solid oxide electrolysis cells (SOECs) show significant promise in converting CO2to valuable fuels and chemicals, yet exploiting efficient electrode materials poses a great challenge. Perovskite oxides, known for their stability as SOEC electrodes, require improvements in electrocatalytic activity and conductivity. Herein, vanadium(V) cation is newly introduced into the B-site of Sr2Fe1.5Mo0.5O6-δperovskite to promote its electrochemical performance. The substitution of variable valence V5+for Mo6+along with the creation of oxygen vacancies contribute to improved electronic conductivity and enhanced electrocatalytic activity for CO2reduction. Notably, the Sr2Fe1.5Mo0.4V0.1O6-δbased symmetrical SOEC achieves a current density of 1.56 A cm–2at 1.5 V and 800 °C, maintaining outstanding durability over 300 h. Theoretical analysis unveils that V-doping facilitates the formation of oxygen vacancies, resulting in high intrinsic electrocatalytic activity for CO2reduction. These findings present a viable and facile strategy for advancing electrocatalysts in CO2conversion technologies.

Lithium‐ion capacitor (LIC) is a promising energy storage device, which combines double advantages of high‐energy lithium‐ion batteries (LIBs) and high‐power supercapacitors. However, the reported anode materials for LICs are synthesized based on the high‐purity chemicals under complicated and time‐consuming conditions, which exhibit a prohibitive cost in practical application. Herein, natural molybdenite is employed as the precursor to construct a high‐capacity and low‐cost anode material of LICs. Specifically, molybdenite is exfoliated into thin‐layer MoS2under the interaction of hydrazine hydrate and sodium hydroxide, and then coupled with reduced graphene oxide to form a MoS2@rGO composite. Resulting from high reactive activity and structural stability, the MoS2@rGO anode shows excellent lithium‐ion storage performance including high specific capacity (936 mAh g−1at 100 mA g−1) and rate capability (446 mAh g−1at 5000 mA g−1). By using MoS2@rGO as an anode and activated carbon as a cathode, the assembled LIC device provides a maximum energy density of 105 Wh kg−1. Even at a high power density of 25 000 W kg−1, the energy density is still up to 65 Wh kg−1. This work provides a reference for the commercial utilization of natural molybdenum resources in the energy storage field. Natural molybdenite is being used as raw material to prepare high‐performance lithium‐ion capacitor composite anode material with unique multilayer structure by simple stripping and self‐assembly method. The formation of the composite interface between molybdenite and reduced graphene oxide can effectively promote the transport and charge transfer of lithium ions. This also helps to realize the efficient performance of lithium‐ion capacitors.

Lithium-ion capacitors (LICs) are considered to be promising power sources due to their combination of high-rate capacitors and high-capacity batteries. However, development of a high-performance LIC is still restricted by the sluggish intercalation reaction and unsatisfied specific capacities in battery-type bulk anodes. To overcome these issues, herein, we utilize two-step atomic layer deposition (ALD) to realize a uniform coating of FeOxand TiO2on CuO nanorods, which results in the formation of ternary CuO@FeOx@TiO2composite. After further treatment in H2/Ar atmosphere, the as-derived Fe3O4is encapsulated between conductive Cu nanorod and hollow TiO2shell (denoted as Cu@Fe3O4@TiO2). Owing to the rational design, the binder-free Cu@Fe3O4@TiO2electrode exhibits an ultrahigh Li-ion storage capacity (1585 mA h g–1at 0.2 A g–1), superior rate capability, and excellent cycle performance (no decay after 1000 cycles), which could efficiently boost the energy-storage capability of LICs. By employing an anode of Cu@Fe3O4@TiO2and a cathode of activated carbon, the as-constructed full LIC device provides high energy//powder densities (154.8 Wh kg–1at 200 W kg–1; 66.2 Wh kg–1at 30 kW kg–1). These superior results demonstrate that ALD-enabled architectures hold great promise for synthesizing high-capacity anodes for LICs.

The development of an efficient, robust, and low-cost catalyst for water electrolysis is critically important for renewable energy conversion. Herein, we achieve a significant improvement in electrocatalytic activity for both the oxygen-evolution reaction (OER) and the hydrogen-evolution reaction (HER) by constructing a novel hierarchical PrBa0.5Sr0.5Co2O5+δ(PBSC)@FeOOH catalyst. The optimized PBSC@FeOOH-20 catalyst consisted of layered perovskite PBSC nanorods and 20 nm thick amorphous FeOOH nanoflakes exhibiting an excellent electrocatalytic activity for the OER and the HER in 0.1 M KOH media, delivering a current density of 10 mA cm–2at overpotentials of 390 mV for the OER and 280 mV for the HER, respectively. The substantially enhanced performance is probably attributed to the hierarchical nanostructure, the good charge-transfer capability, and the strong electronic interactions of FeOOH and PBSC. Importantly, an alkaline electrolyzer-integrated PBSC@FeOOH-20 catalyst as both the anode and cathode shows a highly active overall water splitting with a low voltage of 1.638 V at 10 mA cm–2and high stability during continuous operation. This study provides new insights into exploring efficient bifunctional catalysts for overall water splitting, and it suggests that the rational design of the oxyhydroxide/perovskite heterostructure shows great potential as a promising type of electrocatalysts.

Solid oxide electrolysis cells (SOECs) show great promise in converting CO2to valuable products. However, their practicality for the CO2reduction reaction (CO2RR) is restricted by sluggish kinetics and limited durability. Herein, we propose a novel medium-entropy perovskite, Sr2(Fe1.0Ti0.25Cr0.25Mn0.25Mo0.25)O6−δ(SFTCMM), as a potential electrode material for symmetrical SOEC toward CO2RR. Experimental and theoretical results unveil that the configuration entropy of SFTCMM perovskites contributes to the strengthened metal 3d–O 2p hybridization and the reduced O 2p bond center. This variation of electronic structure benefits oxygen vacancy creation and diffusion as well as CO2adsorption and activation and ultimately accelerates CO2RR and oxygen electrocatalysis kinetics. Notably, the SFTCMM-based symmetrical SOEC delivers an excellent current density of 1.50 A cm–2at 800 °C and 1.5 V, surpassing the prototype Sr2Fe1.5Mo0.5O6−δ(SFM, 1.04 A cm–2) and most of the state-of-the-art electrodes for symmetrical SOECs. Moreover, the SFTCMM-based symmetrical SOEC demonstrates stable CO2RR operation for 160 h.

Sodium metal is one of the most promising anodes for the prospective low-cost rechargeable batteries. Nevertheless, the commercialization of Na metal anodes remains restricted by sodium dendrite growth. Herein, halloysite nanotubes (HNTs) were chosen as the insulated scaffolds, and Ag nanoparticles were introduced as sodiophilic sites to achieve uniform sodium deposition from bottom to top under the synergistic effect. Density functional theory (DFT) calculation results demonstrated that the presence of Ag greatly increased the binding energy of sodium on HNTs/Ag (−2.85 eV) vs HNTs (−0.85 eV). Meanwhile, thanks to the opposite charges on the inner and outer surfaces of HNTs, faster Na+transfer kinetics and selective adsorption of SO3CF3–on the inner surface of HNTs were achieved, thus avoiding the formation of space charge. Accordingly, the coordination between HNTs and Ag afforded a high Coulombic efficiency (about 99.6% at 2 mA cm–2), long lifespan in a symmetric battery (for over 3500 h at 1 mA cm–2), and remarkable cycle stability in Na metal full batteries. This work offers a novel strategy to design a sodiophilic scaffold by nanoclay for dendrite-free Na metal anodes.

Seeking highly efficient, stable, and cost-effective bifunctional electrocatalysts of rechargeable Zn–air batteries (ZABs) is the top-priority for developing new generation portable electronic devices. For this, the rational and effective structural design, interface engineering, and electron recombination on electrocatalysts should be taken into account to reduce the reaction overpotential and expedite the kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we construct a MnCo-based metal organic framework-derived heterogeneous MnS–CoS nanocrystals, which are anchored on free-standing porous N-doped carbon fibers (PNCFs) by the in situ growth method and vulcanization process. Benefiting from the abundant vacancies and active sites, strong interfacial coupling as well as favorable conductivity, the MnS–CoS/PNCFs composite electrode delivers a mentionable oxygen electrocatalytic activity and stability with a half-wave potential of 0.81 V for ORR and an overpotential of 350 mV for OER in the alkaline medium. Of note, the flexible rechargeable ZAB using MnS–CoS/PNCFs as binder-free air cathode offers high power density of 86.7 mW cm–2, large specific capacity of 563 mA h g–1, and adapts to different bending degree of operation. In addition, the density functional theory calculation clarifies that the heterogeneous MnS–CoS nanocrystals reduces the reaction barrier and enhances the conductivity of the catalyst and the adsorption capacity of the intermediates during the ORR and OER process. This study opens up a new insight to the design of the self-supported air cathode for flexible electronic devices.

Sodium-ion hybrid capacitors (SIHCs) are promising technology for energy storage because they combine the merits of high-energy batteries and high-power capacitors as well as naturally abundant sodium resource. However, conventional SIHCs consume a mass of electrolyte during the charge process, thus generating some side reactions at high potentials. In this work, we report a novel rocking-chair SIHC using Na3V2(PO4)3/carbon composite nanofibers (denoted as “NVP@CNF”) as binder-free cathodes and SiO2-templated hollow carbon nanofibers (HCNF) as the capacitive anode. Resulting from the unique carbon-encapsulation configuration, the NVP@CNF cathode demonstrates excellent rate capability (105.8 mAh/g at 0.5C; 66.9 mAh/g at 100C) and long-term cycling stability (98% capacity retention after 2000 cycles) in sodium half-cells. The as-fabricated HCNF||NVP@CNF SIHC device delivers a high energy density of 216.4 Wh/kg at a power density of 381.8 W/kg. Even at an increased power density of 15272.7 W/kg, the energy density is still as high as 123.0 Wh/kg (based on the total mass of active materials in both electrodes). These results provide a new route to design various flexible self-supporting composite fiber electrodes through a simple electrospinning encapsulation strategy, which finally pushes the development of next-generation hybrid energy storage devices.

A facile and bottom-up approach has been presented to prepare 2D Ni-MOFs based on cyanide-bridged hybrid coordination polymers. After thermally induced sulfurization and selenization processes, Ni-MOFs were successfully converted into NiS and NiSe2nanoplates with carbon coating due to the decomposition of its organic parts. When evaluated as anodes of Li-ion batteries (LIBs) and Na-ion batteries (NIBs), NiS and NiSe2nanoplates show high specific capacities, excellent rate capabilities, and stable cycling stability. The NiS plates show good Li storage properties, while NiSe2plates show good Na storage properties as anode materials. The study of the diffusivity of Li+in NiS and Na+in NiSe2shows consistent results with their Li/Na storage properties. The 2D MOFs-derived NiS and NiSe2nanoplates reported in this work explore a new approach for the large-scale synthesis of 2D metal sulfides or selenides with potential applications for advanced energy storage.

Combining high specific surface area (SSA) and superior electrical conductivity together at bulk state is very important for carbon materials in capacitive energy storage applications. Herein, by applying molten sodium metal to activate natural cotton at a relatively low processing temperature (800°C), we have obtained hierarchically porous graphitic carbon fibers (HPGCFs) with SSA up to 1716m2g−1and a high degree of graphitization in the bulk state. This is advantageous compared to amorphous carbon fibers obtained by conventional thermal annealing and KOH-activation. The obtained HPGCFs show remarkable energy storage capability (61% capacitance retention from 1 to 60Ag−1). To further increase the capacitance value, anthraquinone (AQ) molecules have been selected to functionalize HPGCFs via π–π stacking interactions. Asymmetric supercapacitors have been assembled using HPGCFs as the positive electrode and AQ-HPGCFs as the negative electrode in aqueous H2SO4solution. The device presents a large energy density (19.3Whkg−1in the applied potential range between 0 and 1.2V) and ultrahigh power capability (up to 120Ag−1, a full charge–discharge within 0.8s).

Ethyl cellulose (EC) composites modified with 20.0 wt % polyethylenimine (PEI) (PEI/ECs) demonstrated effective hexavalent chromium, [Cr(VI)], removal from solutions with a wide pH range. For example, 4.0 mg/L Cr(VI) solution with a pH below 3.0 was completely purified by 3.0 g/L PEI/ECs within 5 min, much faster than the as-received EC (2 h) and activated carbon (several hours). These PEI/ECs adsorbents has overcome the low pH limitation of Cr(VI) removal; for example, 4.0 mg/L Cr(VI) solution with a pH of 11.0 was completely purified within 15 min. These adsorbents followed chemical adsorption as revealed from the pseudo-second-order kinetic study. These PEI/ECs following the isotherm Langmuir model have a maximum adsorption capacity of 36.8 mg/g, much higher than pure EC (12 mg/g), tetrabutylammonium-modified celluloses (16.67 mg/g), and magnetic carbon (16 mg/g). The reduction of Cr(VI) to Cr(III) by the oxidation of amine groups and hydroxyl groups of PEI/ECs was verified as the main mechanism for the Cr(VI) removal.

To increase the energy density of supercapacitors to approach that of batteries, the current research is always directed towards the cathode materials, whereas the anode materials are rarely studied. In the present work, single-crystalline Fe2O3nanoparticles directly grown on graphene hydrogels are investigated as high performance anode materials for supercapacitors. During the formation of the graphene/Fe2O3composite hydrogels, flexible graphene sheets decorated with Fe2O3particles are self-assembled to form interconnected porous microstructures with high specific surface area, which strongly facilitate charge and ion transport in the full electrode. Infrared spectra show that hydrogen bond is formed between C–OH on graphene hydrogels and Fe2O3. Benefits from the combined graphene hydrogels and Fe2O3particles in such a unique structure are that the graphene/Fe2O3composite electrode exhibits an ultrahigh specific capacitance of 908Fg−1at 2Ag−1within the potential range from −1.05 to −0.3V, and an outstanding rate capability (69% capacity retention at 50Ag−1). Furthermore, the cycling performance is clearly much better for the graphene/Fe2O3composite hydrogels than that for pure Fe2O3sample. These findings open a new pathway to the design and fabrication of three-dimensional graphene hydrogel composites as anode materials in the development of high-performance energy-storage systems.

Anthraquinone (AQ) molecules were selected to decorate the lab-made hierarchical porous carbon nanotubes (HPCNTs) to obtain electrode materials (AQ-HPCNTs) for supercapacitors, which showed a remarkable capacitance increment in comparison with pure HPCNTs when tested in 1 M H2SO4aqueous solution. At a current density of 1 A g–1, the AQ-HPCNTs (mass ratio 7:5) electrode showed an ultrahigh specific capacitance of 710 F g–1, which is much larger than that of the unmodified HPCNTs (304 F g–1). Even at a high discharge current density of 20 A g–1, the specific capacitance of the AQ-HPCNTs (mass ratio 7:5) electrode was still as high as 419 F g–1, indicating an excellent rate capability. Furthermore, all the AQ-HPCNTs electrodes exhibited a long cycle life. Electrochemical behaviors of AQ on the HPCNTs’ surface showed a double pair of redox peaks, which are appropriate for two types of π–π stacking interactions supported by infrared spectra. The excellent capacitive behaviors of the AQ-HPCNTs electrode materials are due to a strong positive synergistic effect between AQ and HPCNTs on the improvement of electrochemical performances.

Controllable synthesis and high yield of functional nanomaterials on conductive substrates are highly desirable for energy conversion and storage applications. In this work, two different porous NiCo2O4nanoarchitectures (including nanowires and nanosheets) are directly grown on carbon cloth collectors, which display a structure-dependence in their capacitive behaviors. Our results show that the nanowire morphology exhibits higher specific capacitance and better cycling performance in the three-electrode configuration. The pseudocapacitive difference is related to the surface area and pore structure of NiCo2O4nanocrystals. This comparison among different morphologies reveals a process–structure–property relationship in electrochemical energy storage.

We report a remarkable transformation of multiwalled carbon nanotubes (MWCNTs) to curved graphene nanosheets (CGN) by the Hummers method. Through this simple process, MWCNTs can be cut and unzipped in the transverse and longitudinal directions, respectively. The as-obtained CGN possess the unique hybrid structure of 1D nanotube and 2D graphene. Such a particular structure together with the improved effective surface area affords high specific capacitance and good cycling stability during the charge–discharge process when used as supercapacitor electrodes. The electrochemical measurements show that CGN exhibit higher capacitive properties than pristine MWCNTs in three different types of aqueous electrolytes, 1 M KOH, 1 M H2SO4, and 1 M Na2SO4. A specific capacitance of as high as 256 F g–1at a current density of 0.3 A g–1is achieved over the CGN material. The improved capacitance may be attributed to high accessibility to electrolyte ions, extended defect density, and increased effective surface area. Meanwhile, this high-yield production of graphene from low cost MWCNTs is important for the scalable synthesis and industrial application of graphene. Furthermore, this novel CGN nanostructure could also be promisingly applied in many fields such as nanoelectronics, sensors, nanocomposites, batteries, and gas storage.

Solar-driven interfacial evaporation is regarded as one of the most promising technologies to address the critical issue of global water scarcity. However, a great deal of energy is lost via conduction during the interfacial evaporation process. Herein, a self-floating Janus evaporator containing micron-sized isolated bubbles that can enhance heat localization is designed. The evaporator is synthesized by gas foaming polyacrylonitrile (PAN) nanofibers and subsequently depositing polypyrrole (PPy). The hydrophilic PAN nanofiber layer on the bottom of the evaporator with abundant macropores can continuously pump water upward through the capillary force. The hydrophobic PAN@PPy composite nanofiber layer on the top possesses a broadband solar absorption property, converting solar irradiation to heat efficiently. The low thermal conductivity of the isolated micron-sized bubbles enhances the thermal insulation of the obtained PAN foam@PPy Janus evaporator, while the stretching and expanding of the nanofibers induced by the bubbles contribute to its increased mechanical stability. This work offers a simple route to fabricate evaporators that can continuously produce drinking water from brine under sunlight, and provides a fresh idea to enhance the thermal insulation and mechanical properties of the conventional electrospinning-based fiber scaffold.