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The dual modification of MXene hybridization and cut-off voltage adjustment endows MoS2/Ti3C2Tx with enhanced reaction kinetics and satisfactory electrochemical performance.

A polyvinyl alcohol/cellulose nanofibers/dimethyl sulfoxide hydrogel electrolyte with superior freezing tolerance was fabricated and applied in zinc-ion hybrid supercapacitors.

The VSe2–ZrO2/C/MXene composite derived from a MXene-MOF hybrid with excellent cycling stability and high reversible capacity exhibited satisfying lithium-ion storage performancedde.

A MoS2/Ti3C2Tx hybrid with dual modification of the reaction kinetics and SEI layers in ether-based electrolyte exhibits excellent sodium storage performance.

Magnesium ion supercapacitor assembled by MoS2 with expanded layer spacing as the anode displays larger capacitance and excellent long-term cycling stability.

K+ intercalated MnO2 as the cathode material for aqueous magnesium-ion hybrid supercapacitors exhibits high energy density and ultra-long cycling life.

The amorphization design of MoO2/MoS2in situ supported by nitrogen-doped carbon leads to robust sodium storage performance at low temperatures.

KFSI salt as an additive in electrolyte can enable highly reversible and nondendritic plating–stripping of Na metal anodes.

An N-doped carbon@Cu core–shell photothermal material with rapid thermal response and superior evaporation rate was prepared and applied for solar desalination.

The state-of-art progress of alloy-type anodes for potassium-ion batteries and their K+ storage mechanism and structure-property relationship are summarized.

A novel memristor with the physical mechanism attributed to a hybridization state transition driven by reversible electric fields.

Here, we introduce a new strategy using urea for the synthesis of carbon-incorporated 2D Fe3O4 (2D-Fe3O4/C) nanoflakes under solvothermal conditions with the following pyrolysis process under an inert atmosphere. Thanks to the structural advantages of 2D-Fe3O4/C, including 2D flakes providing a larger accessible surface area and exposing more active sites, as well as carbon incorporation promoting electrical conductivity for faster charge transfer, the 2D-Fe3O4/C displays a high specific capacitance of 386 F g−1 at 1 A g−1 in a three-electrode system. More importantly, when further assembled into a hybrid supercapacitor with pre-synthesized NiCo-layered double hydroxides as positive electrodes, the assembled supercapacitor device delivers a high-energy density of 32.5 W h kg−1 at 400 W kg−1 and little capacitance loss with bending angles ranging from 0° to 180°. As another capacitive application in desalination, 2D-Fe3O4/C also shows a high desalination capacity of 28.5 mg g−1 over 7.5 min, which suggests a very high mean desalination rate of 3.8 mg g−1 min−1. Our results not only highlight the significance of 2D metal oxide nanosheets/nanoflakes, but also hold great potential for high-performance capacitive applications in supercapacitors and desalination.

Due to their outstanding flexibility and high sensitivity, stretchable ionic conductive hydrogel-based sensors are considered one of the best candidates for the real-time monitoring of human body motion as a wearable health-care detection electronic device. In the detection of body motion, the ionic conductive hydrogel is sensitive to its deformation. However, the current reported hydrogels struggle to recover their initial shape after numerous repeated stretching cycles owing to fatigue, leading to their response insensitivity and service life degradation. In this work, a super-stretchable and recoverable ionic conductive hydrogel (double network polymer hydrogel (SA–Zn): ZnSO4/sodium alginate/poly acrylic-acrylamide) was designed as a stretchable sensor for human body motion detection. The SA–Zn hydrogel exhibited outstanding stretchability (up to 4000% tensile strain) and excellent shape self-recovery ability (20 min recovery time). After self-recovery for 50 cycles, the hydrogel still retained good flexibility, stable self-recovery ability and high conductivity. More importantly, the assembled wireless wearable stretchable sensor (SA–Zn-W) could transform human body motion into a visual electrical signal when combined with a Wi-Fi transmitter, revealing its excellent sensitivity, fast response, effective identification and stable electromechanical repeatability. The superior performance of the SA–Zn-W offers a promising solution for effectively and remotely detecting human body motion.

With the rapid development of flexible wearable electronic devices and the growing energy demands of modern society, flexible energy storage equipment is attracting increasing attention. Recently, flexible Zn-ion hybrid supercapacitors (ZHSs), as a new type of flexible energy storage device, have been reported. However, the limited energy density of the currently reported flexible ZHSs should be further improved to realize their large-scale applications. Herein, we designed a novel redox bromide-ion additive hydrogel electrolyte (SA–Zn–Br) for flexible Zn-ion hybrid supercapacitors (BH-ZHSs) via the introduction of extra faradaic contributions (3Br−/Br3−) into the hydrogel electrolyte to improve their energy density. Additionally, the assembled flexible BH-ZHS displays a maximum energy density of 605 W h kg−1 at a power density of 1848 W kg−1 at an amazing voltage of 2.6 V, which is better than that of most reported flexible ZHSs. After a 5000 cycle charge/discharge cycling test, capacity retention of 87.7% is retained. Interestingly, the strong interactions between the charged groups and Zn2+ ion in the SA–Zn–Br hydrogel electrolyte can harmonize Zn2+ migration with uniform nucleation on a Zn foil surface, leading to layered zinc deposition. Additionally, the SA–Zn–Br hydrogel electrolyte can also serve as an inhibitor of water/oxygen, resulting in the mitigation of corrosion and highly reversible zinc stripping/depositing. The strategy described in this study should provide a new insight for exploring flexible ZHSs with boosted energy density and controllable zinc deposition.

Capacitive deionization (CDI) has emerged as a promising alternative for saline water desalination, yet the relatively slow desalination rate curtails its practical application. Motivated by the goal of simultaneously enhancing the desalination capacity and rate, this paper reports a new type of flow-through rocking-chair capacitive deionization (FTE-RCDI) system for the first time utilizing a sodium-pre-intercalated MnO2 coated carbon nanofiber aerogel (CNFAs@NaxMnO2) as the flow-through electrode. The performance of the FTE-RCDI system in terms of desalination capacity, desalination rate, and energy consumption is systematically studied. Owing to the integration of the unique dual-mode of sodium storage, high redox-active surface area, and good electrical conductivity of the CNFAs@NaxMnO2 and the superior flow-through cell architecture into one, the as-designed FTE-RCDI system exhibits excellent desalination performance with a desalination capacity of 59.35 mg g−1, desalination rate up to 0.46 mg g−1 s−1 (almost the highest value among those of all the reported CDI related systems), and a specific energy consumption as low as 0.55 J mg−1. This work is interesting because it not only exemplifies the significance in both the rational design of electrode materials and the cell architecture for boosting CDI performance, but also provides inspirations for the future design of highly efficient CDI systems.

Developing a high-performance capacitive deionization (CDI) system with both high desalination capacity and fast desalination rate is an urgent requirement to solve fresh-water shortage problems. Herein, we report the design of a highly efficient flow-through pseudo-capacitive deionization (FTE-PCDI) system based on the usage of pseudo-capacitive MoC nanoparticle-embedded carbon nanofiber aerogels (MoC@CNFAs) as flow-through electrodes. The as-synthesized MoC@CNFAs, derived from processing molybdate-incorporated natural bacterial cellulose by a simple solid-state reaction, show excellent pseudo-capacitive performance as well as good mechanical strength. Such merits of MoC@CNFAs make them perfect candidates as flow-through electrodes for FTE-PCDI. By integrating the advantages of both the MoC@CNFAs and the flow-through cell architecture into one, the as-fabricated MoC@CNFAs-based FTE-PCDI system exhibits excellent desalination performance (desalination capacity: 37.03 mg g−1; specific energy consumption: 1.61 J mg−1) with an ultra-high desalination rate up to 0.20 mg g−1 s−1, which is significantly higher than that of the existing CDI-related techniques. This study may shed light on the further design of highly efficient CDI systems.

As an important part of artificial intelligence, electronic skin has received more and more attention recently. However, two serious issues, slow self-healing and lack of direction recognition, have limited the burgeoning of electronic skin largely. Herein, for the first time we report a dual network flexible hydrogel, which was synthesized via cross-linking polyvinyl alcohol (PVA) and polyethylenimine (PEI) with 4-formylbenzoboric acid (Bn) to form a polymer network and then incorporating MXene into the polymer network. Due to the synergy of multiple reversible dynamic covalent bonds and supramolecular interactions, the PVA/Bn/PEI/MXene (PBPM) hydrogel exhibits direction-aware and ultrafast self-healing abilities (self-healing time ∼0.06 s) as well as rapid response performance (signal response time ∼0.12 s). Furthermore, an electronic skin strain sensor assembled by using the PBPM hydrogel can not only efficiently detect the movements in different parts of the prosthetic person body but also specifically identify the directions of the movements including head-down/up and wrist-down/up. The flexible PBPM hydrogel in this work has shown great potential in the applications of artificial skin, soft robots, health monitoring and human-machine exchange interfaces.

The exploration of new carbon materials to overcome the rapid performance decay of common carbon materials in oxygenated saline water (i.e., natural saline water) is the biggest challenge for the industrial application of the capacitive deionization (CDI) technology. In this work, we first report the layer-by-layer motif synthesis of 3D interconnected metal–organic framework (MOF) tubes and the derived nitrogen–iron-doped carbon tubes (3D-FeNC tubes) by using continuous polymeric fibers as templates. The elaborately designed 3D-FeNC tubes exhibit multiple advantages, including fast ionic diffusion (originating from the 1D hollow structure of the tubes), efficient electronic pathways and abundant active sites (arising from the 3D interconnected carbon frameworks), which are beneficial for enhancing the oxygen reduction ability. As a consequence, the as-prepared 3D-FeNC tubes exhibit an unprecedented CDI performance in oxygenated saline water with an exceptional salt adsorption capacity of 40.70 mg g−1 and ultrahigh capacity retention of 93.82% even after 200 cycles, highlighting the significance of morphological control and the benefits of hollow structured materials.

New families of materials that may potentially replace dominant carbon electrodes have emerged as a major research hotspot in the field of capacitive deionization (CDI). Here, we report a metal–organic framework (MOF)/polypyrrole (PPy) hybrid, in which conductive PPy nanotubes that are running through each MOF particle have the potential to increase the overall bulk electrical conductivity, thus promoting such a system as a good CDI electrode material. Consequently, the MOF/PPy hybrid shows a high desalination capacity of 11.34 mg g−1, which is amongst those of state-of-the-art CDI electrodes. Moreover, the MOF/PPy hybrid also shows a superior desalination performance for brackish water and good cycling stability, far exceeding typical carbon-based benchmarks. This is the first example of CDI electrodes derived from direct MOF-based materials, highlighting the potential of these hybrid systems as promising materials beyond traditional carbon electrodes.

Brackish water desalination using capacitive deionization (CDI) offers a promising solution to solve water scarcity. Activated carbons are frequently utilized as commercial electrode materials for CDI, however some limitations in their performance have prevented the practical implementation of CDI. The development of mesostructured carbons that can exceed the performance of commercial activated carbons is highly desirable. Herein, we report the first preparation of carbon nano-polyhedra with three-dimensional (3D) open highly ordered mesostructures as electrode materials for CDI. Owing to their nano-polyhedral structure with 3D open, highly ordered and well-interconnected mesochannels, the obtained mesoporous carbon materials possess large surface area for ion adsorption and shortened pathways for ion diffusion, giving rise to a high desalination capacity of 14.58 mg g−1, fast desalination rate, and stable cycling ability. More importantly, the desalination capacity of our mesoporous carbon nano-polyhedra is the highest among all mesoporous carbon-based CDI electrodes reported to date. It is believed that our mesoporous carbon nano-polyhedra would be promising for practical CDI application.

Capacitive deionization (CDI), as an emerging desalination technique offering an efficient and green route to obtaining clean water, has attracted worldwide attention. Recently, the utilization of the anode or cathode materials of secondary batteries to build hybrid CDI (HCDI) systems has thrived and become a hot topic in the CDI field. The HCDI system can effectively solve the problem of low desalination capacity of traditional CDI. In this work, metal–organic-frameworks derived NaTi2(PO4)3/carbon (NTP/C) composites were prepared and used as electrode materials for HCDI. The results show that due to the unique porous structure, high specific surface area and good electrical conductivity of NTP/C, the HCDI system with the NTP/C composite cathode and AC anode exhibited excellent desalination performance with a high desalination capacity of 167.4 mg g−1 and good desalination ability. The NTP/C should be a promising candidate as an electrode material for HCDI applications.

Pseudocapacitance, typically occurring on the surface of the electrode material, plays a crucial role in improving the charge/discharge rate of sodium ion batteries (SIBs). In this work, N, S co-doped porous carbon microtubes (SNCTs) are prepared through modified in situ polymerization and subsequent annealing with sublimed sulphur in a nitrogen atmosphere. The one-dimensional porous hollow structure enhances the electrolyte penetration and shortens the sodium-ion diffusion pathway, while the N, S doping improves the electrical conductivity of carbon and offers excess reaction sites for sodium-ion storage. The electrode reactions are dominated by a pseudocapacitive process, which can effectively shorten the sodium-ion diffusion pathway and provide extra capacity, resulting in high-rate capability. When used as anodes for SIBs, SNCTs demonstrate good cycling stability (222 mA h g−1 at 2000 mA g−1 after 800 cycles) and superior rate performance (288 and 252 mA h g−1 at 1000 and 2000 mA g−1, respectively). A room-temperature full cell SIB is further assembled using the SNCT as the anode and commercial Na3V2(PO4)3 as the cathode, which exhibits a high specific capacity of 186.1 mA h g−1 after 50 cycles at 50 mA g−1. This work should provide new insights into carbon-based anode materials as high-performance anodes for SIBs.

Capacitive deionization (CDI) is a prospective cost-efficient technology for ion removal from brackish water. The development and design of new electrode materials with reasonable structures is of special importance for high-performance CDI. Herein, a redox-active covalent organic framework (COF) was first introduced and demonstrated as a novel faradaic cathode material for hybrid CDI (HCDI) applications. Due to the high specific surface area and orderly distribution of the redox unit, COF presented high capacitance of 170.9 F g−1 and typical pseudocapacitive characteristics. Moreover, an N-doped porous carbon with a high surface area and interconnected nanopores was synthesized from the same COF and used as the anode in HCDI. The HCDI system demonstrated the highest salt removal capacity of 22.8 mg g−1 along with a maximum desalination rate of 3.2 mg g−1 s−1 in a 500 ppm NaCl solution. The strategy used in this work should provide a new insight in exploring high-performance electrode materials for desalination applications.

Currently, electrospun carbon nanofibers (ECNFs) have attracted much attention due to their flexibility and easy fabrication. However, ECNFs generally show poor electrical conductivity, greatly limiting their practical application. In this work, flexible hierarchically porous carbon polyhedra embedded carbon nanofibers doped with N and S (NSCPCNF) were synthesized by electrospinning a metal–organic framework ZIF-67 and a thiourea incorporated polyacrylonitrile precursor with subsequent carbonization. Due to the enhanced specific surface area, improved charge transfer ability and pseudocapacitive contribution by N, S dual doping, the as-obtained NSCPCNF shows a much higher specific capacitance of 396 F g−1 at a current density of 1 A g−1 in 1 mol L−1 H2SO4 electrolyte (three-electrode mode) than that of ECNFs (192 F g−1). More importantly, a flexible supercapacitor (FSC) assembled using NSCPCNF electrodes achieves a high specific capacitance of 103 F g−1 at a current density of 0.5 A g−1 (two-electrode mode), and a high energy density of 14.3 W h kg−1 at a power density of 250 W kg−1, which outperforms most of the reported ECNF based FSCs, and it also exhibits a high capacitance retention (107% of the initial value after 3000 charge–discharge cycles) and superior bending stability. The strategy proposed in this work provides the feasibility to explore high-performance flexible electrode materials for FSCs.

Carbon-confined transition metal sulfides (TMS@C), featured with excellent redox reversibility, good electrical conductivity and high theoretical capacity, are considered to be promising anode materials for sodium-ion batteries (SIBs). Unfortunately, a large amount of additional S sources are involved in traditional preparation strategies, such as S powder, thiourea, L-cysteine, etc., resulting in the release of dangerous and poisonous H2S or residues of free S in final products. Therefore, developing a facile approach for eco-friendly synthesis of TMS@C remains a big challenge. Herein, a novel approach is developed to realize the facile fabrication of TMS@C from metal-dithiooxamide chelate (MDC) without additional S sources, which effectively reduces the release of H2S and avoids the residue of free S. In this strategy, dithiooxamide (DTO) with superior coordination ability coordinates with Ni2+ for the fine generation of the Ni-MDC precursor that is converted to N, S-codoped carbon-confined Ni3S2 nanoparticles (Ni3S2@NSC) after an in situ self-carbonization and self-sulfidation process. Benefiting from the rich heteroatoms in DTO, high doping contents of N and S in the carbon matrix can be obtained. When evaluated as an anode material for SIBs, Ni3S2@NSC exhibits excellent sodium storage performance with high reversible capacity (458.1 mA h g−1 after 100 cycles at 0.1 A g−1), superior rate capability (323.3 mA h g−1 at 2 A g−1) and robust long-term cycling stability (392.6 mA h g−1 after 300 cycles at 0.5 A g−1), which outperform those of nickel sulfide-based electrodes reported so far. More importantly, the strategy by employing MDC as a versatile precursor and template in this work should be promisingly applied in the fabrication of other heteroatom-doped TMS@C for efficient energy storage and conversion.

Fe3O4 with a high theoretical specific capacity is a promising anode material for lithium ion batteries (LIBs), but its severe volume variation during the electrochemical process and poor electrical conductivity limit its further applications. To solve these problems, in this work, a self-assembled flower-like Fe3O4/C architecture was successfully synthesized via a simple two-step method including a solvo-hydrothermal self-assembly process and a high temperature in situ carbonization process. Field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption isotherms, galvanostatic charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the morphology, structure and electrochemical performances of the samples, respectively. The flower-like Fe3O4/C showed a high discharge capacity of 1165.4 mA h g−1 after 300 cycles at a current density of 277.2 mA g−1 with excellent rate performances. The superior electrochemical performances were triggered primarily due to the incorporation of carbon into the Fe3O4 moiety comprising a hollow structure which can offer a high specific surface area and excellent charge transfer ability. The designed flower-like Fe3O4/C is a promising anode material for high-performance LIBs.

Nickel sulfide, a promising anode for sodium-ion batteries (SIBs), has drawn a lot of attention due to its natural abundance, low cost, rich types and high theoretical specific capacity (Ni3S2: 446, NiS: 591 and NiS2: 879 mA h g−1). However, the huge volume change induced severe electrode pulverization results in the low specific capacity and poor cycling stability of nickel sulfide electrodes. Herein, in this paper, we developed a metal–organic framework (MOF) strategy to prepare pomegranate-like clusters with small NiS2 nanoparticles anchored on nitrogen doped porous graphitic carbon networks (NiS2/NC) via successive carbonization and sulfidation. When evaluated as an anode for SIBs, the as-prepared NiS2/NC hybrid exhibited a high reversible capacity of 505.7 mA h g−1 after 100 cycles at 0.1 A g−1, excellent rate capability (294.4 mA h g−1 at 3 A g−1) and robust cycling stability with a capacity of 356.2 mA h g−1 after 300 cycles at 0.5 A g−1, which outperforms most of the nickel sulfide based electrodes reported so far. The excellent cycling performance and rate capability for SIBs can be attributed to the unique structure inherited from nickel based MOFs, in situ fabrication strategy, high capacity of NiS2, and conductive and buffering features of the nitrogen-doped graphitic carbon networks, demonstrating the great potential of the as-prepared NiS2/NC hybrid for high-performance SIBs.

TiO2 is now developed as a low-cost and high-safety anode material for sodium-ion batteries (SIBs), but its low sodium ion diffusion ability and poor electrical conductivity hinder its sodium-storage performance. In this work, TiO2 nanocrystals embedded in sulfur-doped porous carbon (TSPC) were synthesized through the solvothermal synthesis of a metal–organic framework MIL-125(Ti) precursor and subsequent pyrolysis with inorganic sulfur powder under a nitrogen atmosphere. The inner TiO2 nanocrystals enlarge the electrode/electrolyte interface and shorten the diffusion distance of sodium ions, while the sulfur-doped porous carbon enhances the electron transport ability, inhibits the aggregation of TiO2 nanocrystals, and offers more reaction sites for sodium storage. Benefiting from the synergetic effects between TiO2 nanocrystals and sulfur-doped porous carbon, when used as the anode material for SIBs, the TSPC demonstrates an ultrahigh specific capacity of 323 mA h g−1 after 100 cycles at 50 mA g−1 and extraordinary cycling stability with a capacity retention of 80.1% after 1500 cycles. The TSPC should be a promising anode material for high-performance SIBs.

The sodium storage performance of recently reported Ti3C2Tx MXenes is seriously restricted by their low specific capacity due to their insufficient interlayer spacing. Herein, for the first time, a sulfur (S) doped multilayered Ti3C2Tx MXene was prepared by a simple sulfidation treatment of Ti3C2Tx using thiourea as the S source, which shows an increased interlayer spacing and enhanced electrical conductivity. When used as an anode for sodium-ion batteries (SIBs), the S-doped Ti3C2Tx exhibits a high reversible capacity of 183.2 mA h g−1 after 100 cycles at 0.1 A g−1, excellent rate capability (121.3 mA h g−1 at 2 A g−1 and 113.9 mA h g−1 at 4 A g−1) and robust long-term cycling stability with a reversible capacity of 138.2 mA h g−1 after 2000 cycles at 0.5 A g−1. Notably, the superior sodium storage performance should be attributed to the multilayered morphology, expanded interlayer spacing and enhanced electrical conductivity as well as the high contribution of surface-induced capacitive behavior after S doping, and it outperforms those of reported Ti3C2Tx based electrodes, highlighting the feasibility of the S doping strategy. Most importantly, this work offers a novel approach for smart design and rational fabrication of heteroatom-doped MXenes for energy storage and conversion applications.

For the first time, N,B dual-doped porous carbon spheres (denoted as PCSs) were prepared through direct carbonization of covalent organic frameworks (COFs) and used as an electrode material for membrane capacitive deionization (MCDI). Due to their high accessible surface area and defect-abundant structure offered by N,B-co-doping, the nanostructured PCSs exhibit high desalination ability and are expected to be promisingly applied in MCDI.

Rational fabrication and structure design of anode materials with high specific capacity and excellent cycling stability are of significant importance for the development of high-performance lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). In this paper, a zeolitic imidazolate framework-8 (ZIF-8) with a unique polyhedral morphology and large size (about 2 μm) was successfully synthesized through a facile co-precipitation method. After successive carbonization and sulfidation, ZnS nanoparticles decorated on nitrogen-doped porous carbon polyhedra (ZnS/NPC) were obtained. When applied as the anode material for LIBs, the ZnS/NPC hybrid displays the highest reversible specific capacity for ZnS-based electrodes reported so far (1067.4 mA h g−1 at 0.1 A g−1 after 200 cycles), excellent rate capability (364.6 mA h g−1 at 4 A g−1), and robust long-term cycling performance (856.8 mA h g−1 at 1 A g−1 after 1000 cycles). As for SIBs, the resultant ZnS/NPC also exhibits a desirable capacity of 370.6 mA h g−1 after 100 cycles at 0.1 A g−1 and 289.2 mA h g−1 after 1000 cycles at 1 A g−1. Such superior lithium and sodium storage performances should be attributed to the distinctive structure advantages inherited from ZIF-8, where the Zn ions were in situ converted to ZnS with high reactivity upon electrochemical cycling and the organic linkers were pyrolyzed to nitrogen-doped porous carbon polyhedra to enhance the conductivity of the hybrid and keep the structure stability during cycling.

Transition metal phosphides, especially Ni2P, are of great interest as promising battery-type electrode materials for hybrid supercapacitors, but their poor electrical conductivity and porosity limit their application. Here, for the first time, the synthesis of carbon-incorporated Janus-type Ni2P/Ni hollow spheres (Ni2P/Ni/C) was reported via simultaneous carbonization and phosphorization of Ni-based metal–organic frameworks (Ni-MOFs). Their unique structural merits include the incorporated carbon content, Janus-type Ni2P/Ni nanocrystals, and high-porosity hollow structure, thus endowing them with a high specific surface area, good electrical conductivity and low density. As a result, the optimized Ni2P/Ni/C exhibits a remarkable specific capacitance of 1449 F g−1 at 1 A g−1 in 2 M KOH aqueous electrolyte in a three-electrode system. A hybrid supercapacitor device was fabricated by using Ni2P/Ni/C as the positive electrode and active carbon as the negative electrode, and it achieves a very high energy density of 32.02 W h kg−1 at a power density of 700 W kg−1 and a remarkable cycling stability (about 99% capacitance retention after 5000 cycles). The Ni2P/Ni/C should be one of the most promising electrode materials for hybrid supercapacitor application.

Here, ultrathin nitrogen-doped carbon/graphene nano-sandwiches were synthesized by carbonization of graphene oxide-based nanosheets, which were fully covered with ultrasmall ZIF-8 nanocrystals. The novel sandwich structure possesses large accessible surface area, excellent electrical conductivity, and high nitrogen content, thus showing superior desalination performance.

In this work, porous carbon spheres with hierarchical pores (denoted as hCSs) were fabricated via a sol–gel process using a surfactant-directing assembly strategy and investigated as capacitive deionization (CDI) electrode materials for the first time. By using transmission electron microscopy and N2 adsorption/desorption analyses, a hierarchy of micropores and mesopores was demonstrated to be present in the hCSs. Based on the results of CDI measurements, the hCSs obtained at 800 °C (hCSs-800) displayed the best electrosorption performance of all the hCS samples tested: hCSs-800 exhibited a high electrosorption capacity of 15.8 mg g−1 when the initial NaCl concentration was 500 mg L−1. Furthermore, according to a Kim–Yoon plot analysis, hCSs-800 integrated the merits of both a high electrosorption capacity and fast electrosorption rate, indicating the superiority of these hCSs for CDI applications.

Sodium-ion batteries (SIBs) have attracted great interest for use as the next generation rechargeable batteries due to the abundant sodium natural resources and similar chemistry of lithium and sodium. TiO2 is an attractive candidate as an anode for SIBs due to its high safety, low cost, appropriate voltage platform and good structural stability during repeated charge–discharge processes. However, the sodium storage mechanism of TiO2 for SIBs remains unclear, which appears to be different from the working mechanism in lithium-ion batteries. This article highlights a recent report by Passerini's group, which successfully proposed a new sodium storage mechanism of TiO2 for SIBs.

TiO2 is a promising anode for sodium-ion batteries (SIBs) due to its inherent safety, low cost, good structural stability during the sodium-ion storage process and appropriate voltage platform. However, unsatisfactory electrical conductivity hinders its applications. Here we demonstrate that doping TiO2 nanotubes with Ni2+via an initial sol–gel method, subsequent hydrothermal process and final thermal treatment can balance the high conductivity and good structural stability of TiO2 to improve the sodium-ion storage performance. The resultant sample exhibits a high charge capacity of 286 mA h g−1 after 100 cycles at a current density of 50 mA g−1 and even at a high current density of 5 A g−1, a capacity of 123 mA h g−1 is maintained after 2000 cycles. It is believed that the strategy in this work can provide a useful pathway towards enhancing the electrochemical performance of TiO2 anodes for SIBs.

Capacitive deionization (CDI) is an emerging technology offering a green and efficient route to obtain clean water. Up to now, the key of CDI technology has been focused on the exploration of electrode materials with a rationally designed structure and excellent performance, because the electrosorption performance of the carbon-based electrodes reported to date cannot meet the demands of practical applications of CDI. Herein, novel graphene/carbon nanotubes (CNTs) hybrid sponge (GNS) structures were designed and fabricated via directly freeze-drying graphene oxide/CNTs mixed solution followed by annealing in nitrogen atmosphere. The morphology, structure and electrochemical performance of GNS were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, nitrogen adsorption–desorption, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that GNS with 20 wt% CNTs has a maximum specific surface area of 498.2 m2 g−1 and a highest specific capacitance of 203.48 F g−1 among all the samples. When used as CDI electrode, it exhibits an ultrahigh electrosorption capacity of 18.7 mg g−1, and, to our knowledge, this value is superior to those of other carbon electrodes reported recently. GNS should be a promising electrode material for high-performance CDI.

Porous CuO/Cu2O composite hollow octahedrons were synthesized simply by annealing Cu-based metal-organic framework templates. When evaluated as anode materials for sodium ion batteries, they exhibit a high maximum reversible capacity of 415 mA h g(-1) after 50 cycles at 50 mA g(-1) with excellent cycling stability and good rate capability.

Ultra-thin carbon nanofiber networks (bc-CNFs) were prepared from natural-based bacterial cellulose pellicle through freeze drying and subsequent carbonization at different temperatures. The morphology, structure and electrochemical performance of the bc-CNFs were characterized by field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, nitrogen adsorption–desorption, Fourier transform infrared spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Their electrosorption performance in NaCl solution was studied and compared with those of carbon nanotubes (CNTs) and electrospun carbon nanofibers (e-CNFs). The results show that the bc-CNFs treated at 800 °C exhibited excellent desalination performance with an electrosorption capacity of 12.81 mg g−1 in 1000 mg l−1 NaCl solution, much higher than those of the CNTs (3.78 mg g−1) and the e-CNFs (6.56 mg g−1). The excellent performance of the bc-CNFs is ascribed to their high specific surface area, low charge transfer resistance and superior hydrophility.

Mesoporous nanostructured Co3O4 was prepared by the direct pyrolysis of a Co-based metal organic framework (MOF) template at a relatively low temperature rather than a high temperature. When tested as an anode material for lithium-ion batteries (LIBs), this porous Co3O4 exhibited a greatly enhanced performance of lithium storage. The capacity of the porous Co3O4 retained 913 mA h g−1 after 60 cycles at a current rate of 200 mA g−1. Excellent rate capability was also achieved. We also found out that the Co3O4 prepared from the MOF template at a relatively low temperature has better electrochemical performance than that prepared at high temperature.

A nitrogen-doped electrospun reduced graphene oxide–carbon nanofiber composite (NG–CNF) was fabricated via electrospinning by adding graphite oxide into a precursor solution and subsequent thermal treatment under an ammonia atmosphere. The morphology, structure and electrochemical performance of the composite were characterized by scanning electron microscopy, nitrogen adsorption–desorption, cyclic voltammetry and electrochemical impedance spectroscopy, and their capacitive and electrosorption performances in NaCl solution were studied. The NG–CNF composite electrode shows excellent specific capacitance (337.85 F g−1) and electrosorption capacity (3.91 mg g−1), much higher than those of pure carbon nanofibers (171.28 F g−1 and 3.13 mg g−1) and the reduced graphene oxide–carbon nanofiber composite (264.32 F g−1 and 3.60 mg g−1). The enhanced performance of the NG–CNF is ascribed to the nitrogen doping and the formation of an effective “plane-to-line” conducting network in the composite, which facilitates the electron transfer and ion transport as well as increases the specific surface area.

Semiconductor photocatalysis has attracted tremendous attention due to its potential in environmental remediation, clean energy production and chemical reaction technology. Pursuing high efficiencies is a core task in the field. One of the major factors in photocatalysis is the limited light absorption of photocatalysts in the incident solar spectrum. In this treatise, we will survey recent advancements in light-conversion phosphor-based composites including up-conversion, down-conversion, and long afterglow phosphor-based composites for photocatalysis.

Nitrogen-doped carbon nanorods (NCNRs) were prepared from naturally based nanocrystalline cellulose through simple freeze drying and subsequent thermal treatment under an ammonia atmosphere at different temperatures. The morphology, structure and electrochemical performance of the NCNRs were characterized using scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption, X-ray photoelectron spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy, and their electrosorption performance in NaCl solution was studied. The results show that NCNRs treated at 1000 °C exhibit an extremely high electrosorption capacity of 17.62 mg g−1 when the initial NaCl concentration is 500 mg l−1, which shows great improvement compared with their undoped counterparts. The nitrogen doping proved to be a very effective method for improving the electrosorption performance, and the NCNRs should be very promising candidates as electrode materials for CDI applications.

Carbon sphere (CS)@Bi2MoO6 core–shell structure (CS@BMO) composites were successfully synthesized via a solvothermal reaction of CSs and Bi2MoO6 precursors in the mixed solution of ethylene glycol and ethanol. The morphology, structure and photocatalytic performance of the composites in the degradation of Rhodamine B (RhB) were characterized by scanning electron microscopy, X-ray diffraction, UV-vis absorption spectroscopy, electrochemical impedance spectra and nitrogen adsorption–desorption, respectively. The results show that the CS@BMO composites exhibit enhanced photocatalytic performance for degradation of RhB with a maximum degradation rate of 95% under visible light irradiation compared with the pure Bi2MoO6. The improved photocatalytic performance is ascribed to the enhanced specific surface area and light absorption as well as the reduced electron–hole pair recombination with the presence of CSs in the composites.

Water-dispersed CdSe/CdS/ZnS core/shell/shell quantum dots (QDs) with the highest quantum yield of 25.4% were first synthesized for each component by microwave irradiation. As-prepared QDs do not only possess a large Stokes shift but also exhibit excellent repeatability. They can convert near UV and blue light with lower sensitivity to the Si solar cell to red light at which the solar cell has higher sensitivity. The fabricated CdSe/CdS/ZnS QDs/SiO2 composite films were applied to Si solar cells as luminescent down-shifting layers and the effect of QDs on the photoelectric conversion efficiency of photovoltaic modules was investigated. Under one sun illumination, the composite film containing an appropriate amount of CdSe/CdS/ZnS QDs effectively enhances the photoelectric conversion efficiency of the Si solar cell by spectral down-shifting as compared to the bare glass substrate, and the maximum achieves 16.14%.

Carbon nanorods (CNRs) were fabricated from natural based nanocrystalline cellulose through a simple thermal treatment at 800, 1000 and 1200 °C. The morphology, structure and electrochemical performance of CNRs were characterized by atomic force microscopy, Raman spectroscopy, nitrogen adsorption–desorption, cyclic voltammetry and electrochemical impedance spectroscopy. Their electrosorption performance in NaCl solution was studied. The results show that CNRs treated at 1200 °C exhibit the highest specific capacitance of 264.19 F g−1 and electrosorption capacity of 15.12 mg g−1 with the initial NaCl concentration of 500 mg l−1, due to their high specific surface area and low charge transfer resistance.

Long afterglow Sr4Al14O25:Eu,Dy phosphors were introduced into the TiO2 photoanode of CdS quantum dot-sensitized solar cells (QDSSCs) as both a scattering and down converting layer, and the photovoltaic performances of the cells were investigated. The results show that the cell with Sr4Al14O25:Eu,Dy achieves a power conversion efficiency of 1.40%, which is an increase of 38% compared to the cell without Sr4Al14O25:Eu,Dy (1.02%). The performance improvement is attributed to enhanced light harvesting via improved light absorption and scattering processes. After a single sun illumination for 1 min and subsequent removal of the light source, the cell with Sr4Al14O25:Eu,Dy could be driven even in the dark by the long persistent light from Sr4Al14O25:Eu,Dy.

A fast microwave-assisted approach was developed to fabricate carbon microspheres (CSs) using sucrose as the precursor in a microwave system. After thermal treatment at 300, 500, 700 and 1000 °C, the CSs were used as anode materials for sodium ion batteries (SIBs). The results show that CSs treated at 500 °C exhibit a maximum capacity of 183 mA h g−1 at a current density of 30 mA g−1 after 50 cycles, and even at a high current density of 1000 mA g−1 a capacity of 83 mA h g−1 is maintained. The high capacity, good cycling stability and excellent rate performance of CSs, due to their unique spherical structure, make them a promising candidate for anode materials for SIBs.

Y(3)Al(5)O(12):Ce phosphors have been prepared and used as an effective scattering layer on top of a transparent layer of nanocrystalline TiO(2) for dye sensitized solar cells (DSSCs). The Y(3)Al(5)O(12):Ce scattering layer increases the photocurrent of DSSCs due to the enhanced light harvesting mainly via the improved light absorption and scattering. Under one sun illumination (AM 1.5G, 100 mW cm(-2)), a high efficiency of 7.91% was achieved for the cell with a Y(3)Al(5)O(12):Ce scattering layer, which is an increase of 13.5% compared to the cell without a scattering layer (6.97%).

Bi2O3/F–TiO2 composites were successfully synthesized via an aqueous precipitation method. Their morphologies, structures and photocatalytic performance in the degradation of methyl orange (MO) were characterized by scanning electron microscopy, X-ray diffraction, UV-vis absorption spectroscopy and photoluminescence spectroscopy. The results show that the Bi2O3/F–TiO2 composites exhibit enhanced photocatalytic performance in the degradation of MO with a maximum degradation rate of 95% under visible light irradiation for 180 min, which is mainly ascribed to the increase in light adsorption and the reduction in electron–hole pair recombination in Bi2O3 with the introduction of F–TiO2.