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[Display omitted] • Discussed MXene-based capacitive deionization (CDI) electrode optimization. • Presented forefront applications of MXene-based CDI across multiple fields. • Envisaged challenges and future directions for MXene-based CDI. MXene, hailed for its hydrophilicity, conductivity, and modifiable interlayer spacing, emerges as a frontrunner in capacitive deionization (CDI) electrode materials. Yet, pristine MXene grapples with suboptimal ion removal and stability. This review delves into inventive strategies to fortify MXene-based CDI electrodes, spotlighting their avant-garde applications in combatting ion pollution, reclaiming resources, softening water, and thwarting bacteria. Future prospects for MXene in CDI are also deliberated, aimed at igniting inspiration in the CDI arena. Some strategies proposed herein can be applied to other electrode materials in the CDI domain, thus fostering advancement across the entire spectrum of CDI electrode materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A NF/Mn 2 CoO 4 @MoO 2 electrode was prepared for Pb2+-targeted removal via CDI technology. • SCR of the electrode relies on preferential adsorption and sluggish desorption for Pb2+. • Synergistic effects of Mn 2 CoO 4 and MoO 2 are beneficial for Pb2+ capacitive removal. • Theoretical calculations confirm SCR is due to stronger bonding between Pb2+ and MoO 2. • Electrodepositing loaded MoO 2 onto NF/Mn 2 CoO 4 for 60 min achieved optimum capacitance. To achieve targeted removal of Pb2+ from industrial wastewater, a NF/Mn 2 CoO 4 @MoO 2 composite electrode, synthesised using the hydrothermal method combined with electrodeposition technology, was employed to construct an asymmetric capacitive deionization (CDI) system to selectively electro-adsorb and desorb Pb2+ ions. The electrode exhibited pseudocapacitive characteristics in solutions containing Pb2+, facilitating rapid and reversible redox reactions. The asymmetric CDI system, utilising graphite paper as the positive electrode and NF/Mn 2 CoO 4 @MoO 2 as the negative electrode, displayed exceptional adsorption performance at 1.4 V for 1 h, decreasing the Pb2+ concentration from 50 ppm to 4 ppb, achieving an adsorption capacity of 156.24 mg g−1, and displaying outstanding cyclic stability. Moreover, the electrode demonstrated preferential adsorption of Pb2+ in mixed solutions containing multiple heavy metal ions, with relative removal coefficients of 4.48 − 19.86 compared with other ions. Analysis of the adsorption mechanism indicated that during the adsorption process, Pb2+ was embedded between MoO 2 layers, disrupting the electron cloud symmetry and triggering an oxidation reaction. Octahedral MoO 2 then lost electrons and transformed into tetrahedral [MoO 4 ]2-, forming PbMoO 4 with embedded Pb2+ between the layers, and achieving effective removal of Pb2+ with high selectivity. Molecular dynamics simulations and density functional theory (DFT) calculations confirmed the high selectivity of the prepared electrode for Pb2+ ions based on stronger binding of Pb2+ to MoO 2 than other ions. The electrode has application potential for the capacitive removal of Pb2+ from industrial effluent through CDI technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemical techniques for uranium extraction from water were reviewed. • The strengths, limitations, applicability of each method were evaluated. • The fouling of membranes and electrodes is a main challenge. • Environmental and economic considerations are discussed. Electrochemical removal of uranium from water is an emerging topic that addresses the treatment of drinking water, remediation of contaminated sites, and mining from seawater. Electrochemical strategies compare favorably to conventional processes, such as adsorption and coagulation/flocculation, with advantages in speed and efficiency, materials regeneration, uranium recovery, and recycling. This review assesses all published work on electrochemical techniques for uranium extraction from water, including capacitive deionization (electrosorption), electrodeposition, electrodialysis, and electrocoagulation. This work compares these approaches with conventional techniques and discusses their applicability in different use cases. Environmental and economic considerations are discussed, as well as the current outlook and opportunities for engagement in this emerging field. [ABSTRACT FROM AUTHOR]

• A novel capacitive deionization with a three-phase architecture (T-CDI) was proposed. • Cathodic oxygen reduction was enhanced in T-CDI without affecting desalination. • SAC value and H 2 O 2 generation were 14.91 mg/g and 25.55 mg/L, respectively. • Simultaneous desalination and organics control was achieved by T-CDI/UV. • Applicability of T-CDI in long-term operation was investigated. Cathodic oxygen reduction, as a Faradaic side reaction, has been proven to be thermodynamically favorable for H 2 O 2 generation in capacitive deionization (CDI), which may provide a greener manner for organics control alongside desalination. However, the low levels of dissolved oxygen (DO) in saline water and its potential Faradaic degradation of carbon-based electrodes limit the H 2 O 2 generation in the conventional CDI (C-CDI). Herein, a novel three-phase CDI architecture (T-CDI) was proposed to simultaneously achieve stable desalination and supplementary H 2 O 2 generation. Unlike C-CDI architecture, T-CDI was open-ended at the cathode side, where porous nickel foam was used as current collector and air diffusion layer. Accordingly, a stable gas–liquid-solid three-phase interface was created inside the cathode, thus enhancing the diffusion and utilization of atmospheric air and preventing the damaging effects of excessive DO on the electrode. A stable electrosorption and electrocatalysis performance for T-CDI was obtained by regulating electrode hydrophilic-hydrophobic properties, comparing with other CDI configurations, and altering operating conditions. The salt adsorption capacity and H 2 O 2 accumulative concentration were 14.91 mg/g and 25.55 mg/L, respectively. Furthermore, the simultaneous desalination and organics control in T-CDI were investigated with the assistance of UV irradiation (T-CDI/UV). When treating NaCl and sulfamethazine (SMR) mixture solution, T-CDI/UV significantly reduced the irreversible electrode organic fouling and improved the desalination stability. Additionally, the potentially hazardous SMR was effectively removed alongside desalination. Finally, the long-term operation of T-CDI demonstrated that the generated H 2 O 2 cannot induce an additional substantial deterioration in desalination stability. The techno-economic assessment showed T-CDI was economically competitive compared with C-CDI. This study provides insights into the synergy of non-Faradaic and Faradaic processes and further diversifies the application of CDI in water treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel edge-N doped hierarchical carbons were firstly reported for P electrosorption. • The edge-N strategy endowed more accessible active centers and conductive efficiency. • The LNPC900 electrode showed a superior phosphate removal capacity of 533.06 mg g−1. • The system performed well in natural water purification with low P concentration. • The coupling of electrical capacitance and chemical interactions were achieved. Achieving high-efficiency removal of phosphate has been an urgent issue to combat eutrophication and meet ever-stricter emission standards. Electro-assisted adsorption, a mild electrochemical technology, demonstrated great potential for wastewater treatment owing to the merits of considerable removal performance, facile operation, and energy efficiency. Exploring and boosting the properties of electrode materials is exceedingly vital for technological advancement. In this study, the novel edge-N decorated La-doped hierarchical carbon composites (LNPCs) were developed via in-situ nucleation and one-pot pyrolysis strategy as phosphate capture electrodes. The LNPC900 electrode exhibited an ultrahigh phosphate removal capability of 533.06 mg PO 4 3- g−1 at 1.2 V, surpassing most of the reported electrode materials. Furthermore, this electrochemical system also performed well in the purification of natural river water with low phosphate concentration, where the treated concentration was below the first-class emission standard in China (0.5 mg P L−1). Comprehensive analysis and theoretical calculations indicate that the synergistic property of edge-N and small graphitic carbon nanodomains ensured more accessible active centers and conductive efficiency. The superb phosphate removal capability mainly originated from the coupling contribution of the electrical double layer capacitance, ligand exchange, and electrostatic attraction. This study possesses insight into the theoretical basis for the practical application of phosphate electrosorption and provides a new level of the technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D PAA/GO aerogel was a CDI electrode material. • The double "O" in C = O = C = O acts as a charge transfer and activation site. • The maximum UO 2 2+ adsorption capacity of PAA/GO was 898.7 mg g−1. • DFT explores mechanisms of action. The extraction of uranium is crucial for sustaining a consistent nuclear fuel cycle, yet the task of isolating uranyl ions from aqueous solutions presents formidable challenges. Herein, a PAA/GO aerogel was developed using polyacrylic acid-functionalized graphene, wherein the C = O = C = O segment's dual oxygen served both as electrodes for capacitive deionization and as sites for charge transfer and uranyl capture, effectively purifying uranium mine wastewater. Furthermore, under the stringent experimental conditions set at 298 K and a pH of 5.5, the PAA/GO composite demonstrated an impressive adsorption capacity of 898.7 mg g−1. When this composite was further amalgamated into the CDI architecture, it exhibited an impressive 92 % uranium extraction from genuine mine effluent at an unwavering potential of 0.9 V. Through density functional theory (DFT) analyses, the adsorption energies of [UO 2 (H 2 O) 5 ]2+ with the PAA/GO composite involving C = O = C = O ligands displayed the highest value compared with PAA and PAA/GO composite (involving monodentate and bidentate ligands). The Bader charge analysis further indicating the greatest charge loss in the uranium ion. In conclusion, the novel PAA/GO aerogel 3D framework with its specific C = O = C = O regional chain sets a pioneering standard in uranium extraction techniques, showcasing unprecedented efficiency in UO 2 2+ removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The development history of capacitive deionization for defluorination is introduced. • Recent advances of electrode materials have been classified and reviewed. • Defluorination mechanisms have been summarized. • Challenges for engineering applications are presented. • Future perspectives on defluorination by capacitive deionization are provided. The combined need for advanced treatment of fluoridated water and low-energy technologies has inspired researchers to develop more efficient and green methods of fluoride removal. Capacitive deionization (CDI), a novel water treatment technology, has garnered significant attention in the defluorination field due to its exceptional ion selectivity. Recent decades, CDI has achieved remarkable advancements in electrode materials, F− storage mechanisms, and the potential for engineering applications in the realm of F− removal. However, there has been a lack of reviews that highlight design strategies for electrode materials in terms of fluoride ion properties in water and provide insights into key factors for designing CDI structures with excellent performance and promise for scale applications. Herein, starting from the background of fluorine pollution in surface water, and the selective removal of fluorine heavily relies on the crucial role played by electrode materials. Accordingly, all kinds of defluorinated electrode materials are reviewed. Secondly, the defluorination mechanism is summarized especially the distinctions among these processes. Additionally, the challenges existing in the promotion of CDI defluorination to large-scale applications are firstly analyzed in depth. Finally, future research opportunities and prospects by CDI for defluorination are proposed. In summary, CDI shows great potential for removing fluoride ions from water, offering a fresh approach to sustainable water resource management and environmental protection. [ABSTRACT FROM AUTHOR]

[Display omitted] • State of the art in electrosorption of organic compounds (EOC) critically reviewed. • EOC shows promise against poorly adsorbable, highly polar, and ionized pollutants. • Enhanced adsorption and active control of ad-/desorption by electric potential. • Insightful performance parameters proposed to unify rapidly growing EOC research. • EOC application for on-site regenerable adsorbers and in treatment trains discussed. The widespread contamination of water resources with emerging organic contaminants necessitates the development of sustainable and cost-effective water treatment technologies. Adsorption, as a widely used water remediation process, is hampered by severe performance limitations against ionic and hydrophilic organic contaminants. In addition, no facile on-site regeneration techniques are available. Electrosorption of organic compounds (EOC) is a promising alternative to not only improve adsorption performance, but also to facilitate adsorbent regeneration by green electricity. The number of studies on EOC has grown exponentially over the past decades. There are numerous examples showing that applied electric potentials can significantly enhance the adsorption affinity, capacity, and kinetics of conductive carbon adsorbents. However, whether these effects are specific to certain compound classes or more generally applicable remains unclear as well as the optimal criteria for designing EOC processes. Therefore, we critically evaluated the current state of the art of EOC in terms of active control of adsorption and desorption processes and the achievable effects for ionic and neutral organic compounds. Through a detailed consideration of compound speciation and surface chemistry of electrode materials, we derive mechanistic insights into the EOC process and discuss differences between electrosorption of inorganic and organic compounds. We provide definitions and propose insightful performance parameters to unify the rapidly growing EOC research. Potential application scenarios and future research directions are discussed. Overall, EOC is less likely to be a one-fits-all solution for removing contaminants, but adds a valuable tool especially for the hydrophilic and ionic organic contaminants that challenge conventional adsorption processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Scaling up preparation of modified catalysts by direct calcination in air. • Both defects and oxygen-containing groups contribute to performance enhancement. • Electro-Fenton for high pollutant removal kinetics in a wide pH range. • Industrializable case of 30 g catalyst synthesis theoretically for 5.4 m2 electrode. • Lab-scale demonstration for wastewater treatment with capacity of 7.2 L/h. Electro-Fenton (EF) regarded as a green substitution to traditional homogeneous Fenton, produces highly oxidizing OH through in-situ H 2 O 2 electrosynthesis and electrochemical Fe2+ regeneration. One of obstacles that hinders translation of bench-scale EF performance to water treatment practices is the difficulty of scaling up catalyst/electrode preparation in low cost while producing high performance. Here we report scalable preparation of modified carbon catalysts for high-efficiency EF by directly calcinating commercial carbonaceous materials in air. The EF with modified carbon cathode shows high kinetics of 0.296–0.569 min−1 for levofloxacin removal in much wider pH range of 3.0–6.6 using less Fe dosage compared with homogeneous Fenton. This EF system can reduce chemical oxygen demand (COD) of coking wastewater from 312.0 to 99.5 mg L−1 to satisfy wastewater discharge standard in China while consuming low electricity of 1.8–4.9 kWh kg−1 COD−1. We demonstrated the scalability of this EF process by scaling up preparative throughput of catalyst (30 g that can be processed into electrodes with total working areas of 54000 cm2), enlarging electrode size (230 cm−2) and reactor volume with wastewater treatment capacity of 7.2 L/h. This scalability demonstration of EF technology shows the promising potential of achieving low-cost advanced wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Environmental applications of wood-derived monolithic carbon materials were reviewed. • Various synthesis approaches and modification methods were presented. • Remaining challenges and future prospect were also discussed. • Inspirations could be provided to fabricate advanced wood-based carbon materials. Wood-derived monolithic carbon materials have gained great interest and attention owing to their unique porous structure, abundant longitudinally aligned microchannels, excellent electrical conductivity, good chemical and mechanical stability, and tunable multifunctionality. In recent years, there has been a fast proliferation of research regarding wood-derived monolithic carbon materials for environmental applications with tremendous progress achieved. The versatile environmental applications include catalysis, solar evaporation, adsorption, capacitive deionization, microbial fuel cell and electric field disinfection. This review is intended to summarize such progress and highlight the key achievements. The various synthesis approaches and modification methods of wood-derived monolithic carbon materials are also presented. Lastly, the challenges and future prospect of wood-derived monolithic carbon materials in environmental applications are discussed. This review will provide a deeper understanding of wood-derived monolithic carbon materials for environmental applications and provide inspirations to fabricate advanced wood-based carbon materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The preparation process of the CDI electrode is simplified. • Laser-induced graphene (LIG) can be directly used as a CDI electrode. • LIG electrode is modified by one-step electrodeposition of Co 4 S 3. • The LIG6/Co 4 S 3 -15 presents a high adsorption capacity of 2702.79 mg g−1. • UO 2 2+ adsorption is attributed to the synergistic action of EDLs and pseudocapacitance. It has been proved that capacitive deionization (CDI) technology possesses a significant potential for uranium capture. However, the CDI performance has been limited by the complex preparation process of the electrodes and the poor adhesion between electrode materials and collectors. Here we combine the laser-induced graphene (LIG) and the electrodeposition to develop the LIG/cobalt sulfide (LIG/Co 4 S 3) electrodes with good adsorption performance. The obtained LIG6/Co 4 S 3 -15 electrode has both electrical double layers (EDLs) and pseudocapacitance properties, with a specific capacitance of 24.27 F g−1, which is 1.82 times higher than that of LIG6 (13.36 F g−1). The LIG6/Co 4 S 3 -15 electrode exhibited a high adsorption capacity of 2702.79 mg g−1. The advantages of this electrode preparation method are mainly attributed to the synergistic effect of the following aspects: (i) simplified graphene preparation by avoiding wet chemistry and post-treatment steps; (ii) simplified tedious electrode preparation such as electrode slurry distribution and sheet coating; (iii) the three-dimensional structure of LIG provides not only the conductive network but also the site for Co 4 S 3 nanosheet growth, thus avoiding nanosheet aggregation. The abundant pore structure of the conductive graphene substrate and the layered structure of the Co 4 S 3 nanosheets enable the LIG6/Co 4 S 3 -15 electrode with fast charge/ion transport, high hydrophilicity and superior pseudocapacitance, allowing uranyl (UO 2 2+) to be firstly electrosorbed, then physicochemically adsorbed, and finally electrocatalytically reduced/deposited onto the electrode. This study will offer a simple and environmentally friendly method for the synthesis of electrodes and provide a reference for the design of efficient electroadsorption materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Geosmin and MIB removal by O 2 NBs was investigated under freshwater conditions. • Volatilization and oxidation were the two main removal mechanisms by O 2 NBs. • Nanobubbles/microbubbles mixing enhanced the formation of •OH radicals. • Organic matter, alkalinity and chloride inhibited the oxidative removal pathway. Nanobubbles (NBs) have emerged for water/wastewater treatment, removal of pollutants from sediments and soils, and other environmental and biomedical applications. In this study, the application of NB technology was investigated to control extracellular geosmin and 2-methylisoborneol (MIB) which are naturally occurring terpenoid alcohols produced by cyanobacteria (blue-green algae) and actinomycetes (bacteria) found in surface waters. In addition, their removal mechanisms by oxygen NBs were systematically examined. Volatilization was the dominant mechanism for the removal of geosmin (∼40%) and MIB (∼20%) from distilled and deionized water, while oxidation by reactive oxygen species (ROS) brought additional removals up to ∼ 15%. The formation of hydroxyl (•OH) radicals was promoted when NBs were mixed with microbubbles (MBs), while there was no evidence of geosmin/MIB oxidation by either oxygen NBs or MBs alone. Alkalinity decreased the removal rates of both geosmin and MIB by scavenging •OH radicals, while elevated temperature increased the removal of geosmin and MIB due to enhanced volatilization and oxidation. Natural organic matter (NOM) and chloride ion slightly decreased the removal of geosmin and MIB. The effect of pH in the range of 3–10 was found insignificant. When oxygen NBs were applied to selected natural waters with a wide range of water characteristics, the oxidative pathway was significantly suppressed by ambient alkalinity, NOM, and chloride by which •OH radicals can be quenched. These findings will guide the applications of the oxygen NBs technology in the water treatment, and the further investigations for the improvement of its oxidation potential. [ABSTRACT FROM AUTHOR]

[Display omitted] • Charging activated carbon (AC) tunes adsorption of ionic but not nonionic compounds. • Defunctionalized AC allows better electro-assisted trap&release performance. • Combine surface modification and electric polarization for promoted removal. • Long-term (20 d) stable electro-assisted trap&release with high enrichment effects. • Electro-assisted trap&release promising for on-site AC regeneration. Highly water-soluble, persistent, and mobile organic compounds (PMOCs) are more and more often detected in surface and groundwater, evoking potential threats to the environment and human health. Traditional water treatment strategies, including adsorption by activated carbon materials, fail to efficiently remove PMOCs due to their hydrophilic nature. Electro-assisted sorption processes offer a clean, facile, and promising solution to remove PMOCs on activated carbon-based electrodes and potentially allow an easy on-site sorbent regeneration (trap&release). In this work, the electrosorption of five selected PMOCs, that is, tetrapropylammonium (TPA+), benzyltrimethylammonium (BTMA+), p -tosylate (p -TsO-), p -toluenesulfonamide (p -TSA), and methyl- tert -butyl ether (MTBE), were investigated on two comprehensively characterized activated carbon felt (ACF) types carrying different surface functionalities. Significant enrichment factors in ranges of 102 to 103 for charged PMOCs were expected by our first estimation for electro-assisted trap&release on ACFs in flow systems applying potentials in the range of −0.1 V/+0.6 V vs. SHE for ad-/desorption, respectively. Defunctionalized ACF carrying larger density in surface π-systems and lower O-content promises a higher capability in electrosorption processes than the pristine material in terms of better material stability (tested for 5 cycles over 500 h) and better removal efficiency of ionic PMOCs. To improve ACFs adsorption performance for cationic and anionic PMOCs, permanent chemical surface modification and reversible electric polarization as alternative strategies are compared. Our findings explore future electrode and process design of electrosorption for applications to treat water contaminated by emerging PMOCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel electrochemical reactor is developed for direct synthesis of H 2 O 2 on-site. • Porous solid electrolyte and gas diffusion electrode improve H 2 O 2 production. • H 2 O 2 production efficiency and reactor stability was investigated. • The exhibited a good performance in odor compounds removing combining with UV. The on-site generation of hydrogen peroxide (H 2 O 2) attracts much attention for advanced oxidation processes (AOPs) in water treatment. In this work, we reported a novel on-site H 2 O 2 generation reactor combined with ultraviolet (UV) for taste and odor (T&O) compounds removal in drinking water purification systems. The reactor is equipped with a gas diffusion electrode (GDE) accompanied by a proton-conducting solid electrolyte. In this reactor, GDE is used to improve the oxygen transfer efficiency. The porous solid electrolyte is selected for the proton and electron conduction instead of an electrolyte solution, which is crucial for producing pure H 2 O 2 solution. The production rate and concentration of H 2 O 2 can be controlled through adjusting the applied current efficiency and the flow rate of deionized water in a solid chamber. Meanwhile, this system exhibits long-term stability during a continuous operation for 96 h. For the application of the system, the single-cell was assembled into cell stacks, which improved the H 2 O 2 concentration from 780.9 to 2301.3 mg·L−1, along with the energy consumption reduced from 23.81 to 6.67 kWh·kg−1 under the applied current density of 30 mA·cm−2. To evaluate the water purification performance of this system, the oxidation degradation of 2,4,6-trichloroanisoles (TCA) was conducted using the on-site H 2 O 2 generation process under both static and dynamic flow conditions combined with UV light. The degradation rate of TCA was >95% with its initial concentration of 1 μg·L−1 under the hydraulic retention time from 10 to 40 min−1 and H 2 O 2 dosage from 10 to 100 mg·L−1. Meanwhile, almost no residual H 2 O 2 was detected after the degradation process. This study proposed a promising device for drinking water purification. [ABSTRACT FROM AUTHOR]

In this study, hierarchical porous cellulose/alginate/carbon black hydrogel (CACH) was successfully manufactured by 3D printing method. The 3D-printed CACH can be an effective evaporator in solar steam generation and has great application prospects in seawater desalination and wastewater purification. [Display omitted] • Design of cellulose based solar steam generation through 3D printing. • 3D-printed hierarchically porous structure for customizable solar evaporator. • Macroscopic pore and inherent pore synergistically promoted evaporation efficiency. • Evaporation rate of 1.33 kg m-2h−1 and efficiency of 90.6% was gained. • Seawater desalination and dye wastewater purification using hybrid hydrogel evaporators. Solar steam generation (SSG) has great application prospects in seawater desalination and dye wastewater treatment. However, it is still a challenge to realize a low-cost, rapid evaporation, high water quality and sustainable solar-driven water purification system. Three-dimensional (3D) structural design of evaporator is conducive to promoting evaporation efficiency, which has great potential in SSG field. In this study, 3D hierarchical porous hybrid hydrogel evaporators with embedded carbon black (CB) for SSG are built through 3D printing method. The 3D hierarchically porous cellulose/alginate/carbon black hydrogel (CACH) shows a super-hydrophilic wettability, and excellent light absorption (97%) within the wavelength range from 300 to 2500 nm, which can dramatically improve water transportation capacity and photothermal performance in the evaporator. The evaporation rate of the evaporator is as high as 1.33 kg m-2h−1 and the conversion efficiency of solar energy at 1 kW m−2 (one-sun) solar illumination is up to 90.6%. Moreover, the evaporation also exhibits superior salt resistant performance, and collected water meets World Health Organization (WHO) drinking water standards after purification from seawater. In addition, a small amount of photothermal material (1 wt% CB) is required in this system, which is beneficial to reduce the cost of the system. The 3D-printed hierarchically porous hydrogel evaporator has great application prospects in seawater desalination and wastewater purification. [ABSTRACT FROM AUTHOR]

A self-supported MoS 2 /CoS 2 @TiO 2 nanotube (TNT) hybrid electrode was fabricated by an in-situ hydrothermal process-assisted growth strategy, which achieved a significantly high gravimetric Na+ adsorption capacity and excellent regeneration performance. It also demonstrated amazing removal efficiencies close to 90% for various heavy metal ions (i.e., Fe3+, Cr3+, Cd2+, Pb2+, Cu2+ and Ni2+), revealing its great potential for wastewater purification. [Display omitted] • A self-supported MoS 2 /CoS 2 @TNT hybrid electrode was constructed. • The electrode achieved a gravimetric Na+ adsorption capacity of 44.22 mg g−1. • The electrode exhibited excellent regeneration performance and removal rates. • The electrode also realized removal efficiencies up to 90% for heavy metal ions. Recently, the rational design and construction of graphene-like layered transition-metal disulfides (TMDs) with chemical and physical superiorities to act as capacitive desalination (CDI) electrodes for water purification have attracted increasing interest worldwide. Herein, an advanced self-supported MoS 2 /CoS 2 @TiO 2 nanotube (TNT) hybrid electrode was grown on a TNT scaffold by a hydrothermal process-assisted in-situ growth strategy, and an asymmetric CDI cell was constructed with the as-fabricated MoS 2 /CoS 2 @TNT and commercial AC electrodes as cathode and anode, respectively. Benefiting from the effective structural feature (i.e., fully open nanosheet-assembled flowers and hierarchical pore alignment) and synergy effect of metal-like CoS 2 , state-of-the-art MoS 2 and TNTs with an efficient charge "superhighway", the MoS 2 /CoS 2 @TNT electrode achieved a significantly high gravimetric Na+ adsorption capacity of 44.22 mg g−1 in a 600 mg L−1 NaCl solution at 1.2 V. Moreover, the hybrid electrode possessed excellent regeneration performance with a capacity retention of nearly 100% even after 20 cycles. Most notably, such electrode also demonstrated amazing removal efficiencies close to 90% for various heavy metal ions (i.e., Fe3+, Cr3+, Cd2+, Pb2+, Cu2+ and Ni2+), revealing its great potential for wastewater purification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous hydrogel sponge has been realized via in-situ growth of hydrogel on sponge. • Hydrogel layer can be readily controlled to reserve the porosity of the sponge. • The "porous hydrogel sponge" can be arbitrarily compacted, folded, and twisted. • Water evaporation rate is up to 2.8 kg m-2h−1 under one sun with 332 g h−1 $−1. • Long-term cycling stability (>6 months), as large as 7500 cm2. Hydrogel evaporator is becoming an excellent platform for solar-driven water purification. However, the cost effectiveness and scalability of hydrogel-based evaporate materials is still a great challenge due to the high energy-consuming and time-consuming freeze drying process, as well as limited black hydrogel materials. Herein, inspired by porifera, "porous hydrogel sponge" has been proposed and realized via in-situ growth of novel adhesive/black hydrogel on polyurethane (PU) sponge without freeze drying process for durable and highly efficient solar-driven water evaporation. The in-situ generated hydrogel can firmly adhere on the sponge skeleton just like a skin, and the thickness of the hydrogel layer can be readily controlled to reserve the high porosity of the sponge, while the sponge skeleton can endow the evaporator with desirable mechanical stability (can be arbitrarily compacted, folded, and twisted). The water evaporation rate of the resultant hydrogel evaporator can reach up to 2.8 kg m-2h−1 under one sun with excellent cost-effectiveness at 332 g h−1 $−1. Moreover, the resultant hydrogel evaporator possesses outstanding long-term cycling stability (at least 6 months), and can be as large as 7500 cm2 (can be readily enlarged further). This study represents a new avenue for fabrication and design of high performance hydrogel evaporator toward practical application, and will contribute to the global effort in addressing world water and energy issues. [ABSTRACT FROM AUTHOR]