Constructing Thermal Convection Film for Low Heat Loss and High Salt Resistance in Wood-Based Solar Evaporators.

Unique suspension solar evaporator is one of the effective measures to address the major bottleneck of the emerging interfacial evaporators, i.e., the accumulation of salts on the surface. Yet, it remains a considerable challenge to avoid substantial heat loss underwater. Herein, a suspension wood-based evaporator is proposed with a thermal convection structure that effectively balances the contradiction between salt-resistance ability and heat loss. Benefitting from the heat centralization due to thermal convection, such suspension evaporator exhibits an excellent steam generation rate, which increases from 1.23 to 1.63 kg m-2 h-1 compared to the conventional suspension evaporator. Simultaneously, the steam generation rate retention improves from 64.9% over 20 test cycles to nearly 100% compared to the interfacial evaporator. This work provides an effective pathway for exploring efficient and stable suspension evaporators, offering essential directions for the future development and application of solar-driven evaporation technologies.

Wood-Derived Continuously Oriented Three-Phase Interfacial Channels for High-Performance Quasi-Solid-State Alkaline Zinc Batteries.

Although recently developed hybrid zinc (Zn) batteries integrate the benefits of both alkaline Zn and Zn-air batteries, the kinetics of the electrocatalytic oxygen reaction and mass transfer of the electrolyte, which are limited by the mismatched and disordered multiphase reaction's interfacial transfer channels, considerably inhibit the performance of hybrid Zn batteries. In this work, novel, continuously oriented three-phase interfacial channels at the cathode derived from the natural structure of pine wood are developed to address these challenges. A pine wood chip is carbonized and asymmetrically loaded with a hydrophilic active material to achieve the creation of a wood-derived cathode that integrates the active material, current collector, and continuously oriented three-phase reaction interfacial channels, which allows the reaction dynamics to be accelerated. Consequently, the assembled quasi-solid-state hybrid battery performs an extra charge-discharge process beyond that performed by a typical nickel (Ni)-Zn battery, resulting in a wide operating voltage range of 0.6-2.0 V and a superior specific capacity of 656.5 mAh g-1 , in addition to an excellent energy density (644.7 Wh kg-1 ) and good durability. The ≈370% capacity improvement relative to the Ni-Zn battery alone makes the hybrid battery one of the best-performing alkaline Zn batteries.

Quench-Induced Surface Engineering Boosts Alkaline Freshwater and Seawater Oxygen Evolution Reaction of Porous NiCo2 O4 Nanowires.

The electrochemical oxygen evolution reaction (OER) by efficient catalysts is a crucial step for the conversion of renewable energy into hydrogen fuel, in which surface/near-surface engineering has been recognized as an effective strategy for enhancing the intrinsic activities of the OER electrocatalysts. Herein, a facile quenching approach is demonstrated that can simultaneously enable the required surface metal doping and vacancy generation in reconfiguring the desired surface of the NiCo2 O4 catalyst, giving rise to greatly enhanced OER activities in both alkaline freshwater and seawater electrolytes. As a result, the quenched-engineered NiCo2 O4 nanowire electrode achieves a current density of 10 mA cm-2 at a low overpotential of 258 mV in 1 m KOH electrolyte, showing the remarkable catalytic performance towards OER. More impressively, the same electrode also displays extraordinary activity in an alkaline seawater environment and only needs 293 mV to reach 10 mA cm-2 . Density functional theory (DFT) calculations reveal the strong electronic synergies among the metal cations in the quench-derived catalyst, where the metal doping regulates the electronic structure, thereby yielding near-optimal adsorption energies for OER intermediates and giving rise to superior activity. This study provides a new quenching method to obtain high-performance transition metal oxide catalysts for freshwater/seawater electrocatalysis.

Surfactant-Induced Reconfiguration of Urea-Formaldehyde Resins Enables Improved Surface Properties and Gluability of Bamboo.

The high-efficiency development and utilization of bamboo resources can greatly alleviate the current shortage of wood and promote the neutralization of CO2. However, the wide application of bamboo-derived products is largely limited by their unideal surface properties with adhesive as well as poor gluability. Herein, a facile strategy using the surfactant-induced reconfiguration of urea-formaldehyde (UF) resins was proposed to enhance the interface with bamboo and significantly improve its gluability. Specifically, through the coupling of a variety of surfactants, the viscosity and surface tension of the UF resins were properly regulated. Therefore, the resultant surfactant reconfigured UF resin showed much-improved wettability and spreading performance to the surface of both bamboo green and bamboo yellow. Specifically, the contact angle (CA) values of the bamboo green and bamboo yellow decreased from 79.6° to 30.5° and from 57.5° to 28.2°, respectively, with the corresponding resin spreading area increasing from 0.2 mm2 to 7.6 mm2 and from 0.1 mm2 to 5.6 mm2. Moreover, our reconfigured UF resin can reduce the amount of glue spread applied to bond the laminated commercial bamboo veneer products to 60 g m-2, while the products prepared by the initial UF resin are unable to meet the requirements of the test standard, suggesting that this facile method is an effective way to decrease the application of petroleum-based resins and production costs. More broadly, this surfactant reconfigured strategy can also be performed to regulate the wettability between UF resin and other materials (such as polypropylene board and tinplate), expanding the application fields of UF resin.

Boosting supercapacitive performance of flexible carbon via surface engineering.

The relatively low specific capacitance of flexible carbons hinders their practical application for fabricating high-performance flexible supercapacitors. In this work, a surface engineering method is proposed to boost the supercapacitive performance of the flexible carbon. In this method, a flexible carbon was fabricated from carbon felt via co-activation with potassium argininate and potassium hydroxide (KOH) as activators, and the resulting material is abbreviated as AKCF. Unlike traditional KOH activation processes, the addition of potassium argininate can produce a micro-graphitized carbon layer to be the outer layer of AKCF fibers for achieving better electronic transfer. Due to the improved conductivity and lower charge transfer resistance endowed by a thin micro-graphitized carbon layer, the capacitance of the AKCF-0.1 (0.1 M arginine was used) electrode obtained by the co-activation process is elevated to a 1.8-fold higher value of 403 C·g-1 (2583 mC·cm-2) relative to the AKCF-0 (0 M arginine was used) electrode prepared by KOH activation alone (222 C·g-1 or 1369 mC·cm-2). Moreover, this AKCF-0.1 electrode also displays satisfactory rate capability (66% capacitance retention after a 20-fold current increase) and highly stable cycling performance (no capacitance decline after 20,000 cycles). In addition, the asymmetric supercapacitors constructed with this AKCF-0.1 electrode as the flexible negative electrode expresses high energy densities of 68.4 Wh·kg-1 and 0.139 mWh·cm-2 in aqueous and gel electrolytes, respectively.

Gentle fabrication of colorful superhydrophobic bamboo based on metal-organic framework.

The efficient use of abundant renewable bamboo as high value-added decoration and building materials is of great significance for mitigating carbon dioxide emissions and maintaining sustainable development. The key challenge is to explore efficient and gentle methods to improve the undesirable surface properties of bamboo. Herein, a colorful and superhydrophobic bamboo is gently fabricated by a facile in-situ growth and conversion method based on metal-organic framework (for constructing micro-nano composite structures) and subsequent coating of sodium laurate (for reducing surface energy) at room temperature. The resulting sodium laurate-coated cobalt-nickel double hydroxide layer (CoNi-DH-La) is demonstrated as an efficient superhydrophobic layer to exhibit excellent chemical and mechanical stability. Impressively, the as-obtained CoNi-DH-La-coated bamboo sheet (BS-CoNi-DH-La) shows positive performances in terms of mildew resistance, flame retardancy, and self-cleaning. More importantly, this gentle method can endow bamboo with multiple unfading colors by changing the type of inorganic salts during the preparation process and display good potential for large-scale production.

Rational design of cobalt-nickel double hydroxides for flexible asymmetric supercapacitor with improved electrochemical performance.

Rational design of micro-nano morphology and suitable crystalline structure are highly desired for metal hydroxides to achieve overall high-performance in the advanced electrodes for flexible supercapacitors. Herein, a novel wisteria flower-like microstructure of cobalt-nickel double hydroxide (CoNi-DH) is successfully constructed on carbon cloth (CC) using an in-situ hydrolysis-induced exchange process between hydroxide ions and organic ligands of the Co-MOF in four different kinds of solutions containing Ni2+. The as-prepared wisteria flower-like microstructure grown on CC shows vertically aligned arrays with high specific area and abundant active sites, which not only guarantee the CoNi-DH active materials to be thoroughly exposed in the electrolyte, resulting in highly effective pseudocapacitive energy storage, but also are beneficial to rapid and reversible redox kinetics and thus give rise to high-rate capability. In addition, compared to Ni(NO3)2, NiCl2, and Ni(CH3COO)2 solutions, the Ni2SO4 solution is found to facilitate the formation of the most regular morphology and the largest interlayer spacing on (003) plane of the layered nickel hydroxide phase in the resultant CoNi-DH. As a result, the optimal CoNi-DH-S@CC (CoNi-DH prepared in Ni2SO4) serves as an advanced electrode to show high-rate capability (only 13% Cs decay after a 15-fold current elevation) and a superior specific capacity (Cs) of 929.4 C g-1, which remarkably exceeds those of CoNi-DH-N (823.1 C g-1, in Ni(NO3)2), CoNi-DH-Cl (798.4 C g-1, in NiCl2), CoNi-DH-C (803.8 C g-1, in Ni(CH3COO)2), and other similar metal hydroxides. Moreover, with this CoNi-DH-S electrode as the positive electrode, the as-prepared asymmetric supercapacitor (ASC) delivers an impressive capacity of 204.8 C g-1, a superior energy density of 42.5 Wh kg-1, and satisfactory cycle life (81.5% reservation after 7500 cycles). As a proof-of-concept application, a quasi-solid-state ASC is further successfully fabricated based on the CoNi-DH-S electrode to exhibit encouraging application potential.

Aluminum-doping-based method for the improvement of the cycle life of cobalt-nickel hydroxides for nickel-zinc batteries.

The unsatisfactory cycle life of nickel-based cathodes hinders the widespread commercial usage of nickel-zinc (Ni-Zn) batteries. The most frequently used methods to improve the cycle life of Ni-based cathodes are usually complicated and/or involve using organic solvents and high energy consumption. A facile process based on the hydrolysis-induced exchange of the cobalt-based metal-organic framework (Co-MOF) was developed to prepare aluminum (Al)-doped cobalt-nickel double hydroxides (Al-CoNiDH) on a carbon cloth (CC). The entire synthesis process is highly efficient, energy-saving, and has a low negative impact on the environment. Compared to undoped cobalt-nickel double hydroxide (Al-CoNiDH-0%), the as-prepared Al-CoNiDH as the electrode material displays a remarkably improved cycling stability because the Al-doping successfully depresses the transition in the crystal phase and microstructure during the long cycling. Benefiting from the improved performance of the optimal Al-CoNiDH electrode (Al-CoNiDH-5% electrode), the as-constructed aqueous Ni-Zn battery with Al-CoNiDH-5% as the cathode (Al-CoNiDH-5%//Zn) displays more than 14% improvement in the cycle life relative to the Al-CoNiDH-0%//Zn battery. Moreover, this Al-CoNiDH-5%//Zn battery achieves a high specific capacity (264 mAh g-1), good rate capability (72.4% retention at a 30-fold higher current), high electrochemical energy conversion efficiency, superior fast-charging ability, and strong capability of reversible switching between fast charging and slow charging. Furthermore, the as-assembled quasi-solid-state Al-CoNiDH-5%//Zn battery exhibits a decent electrochemical performance and satisfactory flexibility.

Rational Regulation of Surface Free Radicals on TiO2 Nanotube Arrays via Ag2O-AgBiO3 towards Enhanced Selective Photoelectrochemical Detection.

Due to integrated advances in photoelectrochemical (PEC) functionalities for environment detection applications, one-dimensional (1D) TiO2 nanostructures provide a new strategy (PEC sensors) towards organics detection in wastewater. However, the unidealized selectivity to the oxidation of water and organics limits the PEC detection performance. Herein, we designed a ternary photoanode consisting of Ag2O-AgBiO3/TiO2 nanotube arrays (NTAs) to solve this issue by using a facile one-step precipitation reaction. High oxidation capacity for organics is achieved by regulating the surface free radicals properly through the heterostructure formed between the interface of TiO2 and AgBiO3. More importantly, as a trap for electron capture, Ag2O in this ternary system could not only further improve the separation efficiency of charge carriers, but also capture electrons transferred to the TiO2 conduction band, thus reducing the electrons transferred to the external circuit and the corresponding background photocurrent when detecting organics. As a result, the reconstructed TiO2 NTAs decrease their photocurrent response to water and enhance their response to organics, thus presenting lower oxidation activity to water and higher activity to organics, that is, highly selective oxidation characteristics. This work provides more insights into the impact of charge transfer and surface free radicals on developing promising and efficient PEC sensors for organics.

Facile Construction of Superhydrophobic Surfaces by Coating Fluoroalkylsilane/Silica Composite on a Modified Hierarchical Structure of Wood.

Constructing superhydrophobic surfaces by simple and low-cost methods remains a challenge in achieving the large-scale commercial application of superhydrophobic materials. Herein, a facile two-step process is presented to produce a self-healing superhydrophobic surface on wood to improve water and mildew resistance. In this process, the natural hierarchical structure of wood is firstly modified by sanding with sandpaper to obtain an appropriate micro/nano composite structure on the surface, then a fluoroalkylsilane/silica composite suspension is cast and dried on the wood surface to produce the superhydrophobic surface. Due to the full use of the natural hierarchical structure of wood, the whole process does not need complicated equipment or complex procedures to construct the micro/nano composite structure. Moreover, only a very low content of inorganic matter is needed to achieve superhydrophobicity. Encouragingly, the as-obtained superhydrophobic surface exhibits good resistance to abrasion. The superhydrophobicity can still be maintained after 45 abrasion cycles under the pressure of 3.5 KPa and this surface can spontaneously recover its superhydrophobicity at room temperature by self-healing upon damage. Moreover, its self-healing ability can be restored by spraying or casting the fluoroalkylsilane/silica composite suspension onto this surface to replenish the depleted healing agents. When used for wood protection, this superhydrophobic surface greatly improves the water and mildew resistance of wood, thereby prolonging the service life of wood-based materials.

Hierarchical Micro-Nano Sheet Arrays of Nickel-Cobalt Double Hydroxides for High-Rate Ni-Zn Batteries.

The rational design of nickel-based cathodes with highly ordered micro-nano hierarchical architectures by a facile process is fantastic but challenging to achieve for high-capacity and high-rate Ni-Zn batteries. Herein, a one-step etching-deposition-growth process is demonstrated to prepare hierarchical micro-nano sheet arrays for Ni-Zn batteries with outstanding performance and high rate. The fabrication process is conducted at room temperature without any need of heating and stirring, and the as-grown nickel-cobalt double hydroxide (NiCo-DH) supported on conductive nickel substrate is endowed with a unique 3D hierarchical architecture of micro-nano sheet arrays, which empower the effective exposure of active materials, easy electrolyte access, fast ion diffusion, and rapid electron transfer. Benefiting from these merits in combination, the NiCo-DH electrode delivers a high specific capacity of 303.6 mAh g-1 and outstanding rate performance (80% retention after 20-fold current increase), which outperforms the electrodes made of single Ni(OH)2 and Co(OH)2, and other similar materials. The NiCo-DH electrode, when employed as the cathode for a Ni-Zn battery, demonstrates a high specific capacity of 329 mAh g-1. Moreover, the NiCo-DH//Zn battery also exhibits high electrochemical energy conversion efficiency, excellent rate capability (62% retention after 30-fold current increase), ultrafast charge characteristics, and strong tolerance to the high-speed conversion reaction.

Electrochemically Stable Cobalt⁻Zinc Mixed Oxide/Hydroxide Hierarchical Porous Film Electrode for High-Performance Asymmetric Supercapacitor.

Construction of electrochemically stable positive materials is still a key challenge to accomplish high rate performance and long cycling life of asymmetric supercapacitors (ASCs). Herein, a novel cobalt⁻zinc mixed oxide/hydroxide (CoZn-MOH) hierarchical porous film electrode was facilely fabricated based on a cobalt⁻zinc-based metal⁻organic framework for excellent utilization in ASC. The as-constructed hierarchical porous film supported on conductive Ni foam possesses a rough surface and abundant macropores and mesopores, which allow fast electron transport, better exposure of electrochemically active sites, and facile electrolyte access and ion diffusion. Owing to these structural merits in collaboration, the CoZn-MOH electrode prepared with a zinc feeding ratio up to 45% at 110 min of heating time (CoZn-MOH-45-110) exhibited a high specific capacitance of 380.4 F·g-1, remarkable rate capability (83.6% retention after 20-fold current increase), and outstanding cycling performances (96.5% retention after 10,000 cycles), which exceed the performances of similar active electrodes. Moreover, an ASC based on this CoZn-MOH-45-110 electrode exhibited a high specific capacitance of 158.8 F·g-1, an impressive energy density of 45.8 Wh·kg-1, superior rate capability (83.1% retention after 50-fold current increase), and satisfactory cycling stability (87.9% capacitance retention after 12,000 cycles).

Facile Activation of Commercial Carbon Felt as a Low-Cost Free-Standing Electrode for Flexible Supercapacitors.

High cost, low capacitance, and complicated synthesis process are still the key limitations for carbon-negative materials to meet their industrial production and application in high-energy-density asymmetric supercapacitors (ASCs). In this work, we demonstrate the facile preparation of ultrahigh-surface-area free-standing carbon material from low-cost industrial carbon felt (CF) and its application for flexible supercapacitor electrode with outstanding performance. Through a simple freeze-drying-assisted activation method, the as-prepared activated CF (ACF) was endowed with satisfactory flexibility, ultrahigh specific surface area of 2109 m2 g-1, good electric conductivity (311 S m-1), and excellent wettability to aqueous electrolyte. Owing to these merits, the ACF expressed an ultrahigh areal capacitance of 1441 mF cm-2, a high specific capacitance ( Cs) of 280 F g-1 based on the mass of the whole electrode, and an impressive cycling stability (87% retention after 5000 cycles). When applied as a flexible freestanding electrode for MnO2//ACF ASCs, the ACF-based device provided satisfactory areal energy densities of 0.283 and 0.104 mWh cm-2 in aqueous and quasi-solid electrolytes, respectively. The values outperform many previously reported carbon-based electrochemical devices. The low cost of raw material and the facile fabrication process, together with the high electrochemical performance, make our ACF electrode highly applicable for the mass production of flexible energy-storage devices.

Energy-Saving Synthesis of MOF-Derived Hierarchical and Hollow Co(VO3)2-Co(OH)2 Composite Leaf Arrays for Supercapacitor Electrode Materials.

A one-step and energy-saving method was proposed to synthesize hierarchical and hollow Co(VO3)2-Co(OH)2 composite leaf arrays on carbon cloth, which expressed high capacitance (522 mF cm-2 or 803 F g-1 at the current density of 0.5 mA cm-2), good rate capability (79.5% capacitance retention after a 30-fold increase of the current density) and excellent cycling stability (90% capacitance retention after 15 000 charge-discharge cycles) when tested as a supercapacitor electrode.

Synthesis of NiMn-LDH Nanosheet@Ni3S2 Nanorod Hybrid Structures for Supercapacitor Electrode Materials with Ultrahigh Specific Capacitance.

One of the key challenges for pseudocapacitive electrode materials with highly effective capacitance output and future practical applications is how to rationally construct hierarchical and ordered hybrid nanoarchitecture through the simple process. Herein, we design and synthesize a novel NiMn-layered double hydroxide nanosheet@Ni3S2 nanorod hybrid array supported on porous nickel foam via a one-pot hydrothermal method. Benefited from the ultrathin and rough nature, the well-defined porous structure of the hybrid array, as well as the synergetic effect between NiMn-layered double hydroxide nanosheets and Ni3S2 nanorods, the as-fabricated hybrid array-based electrode exhibits an ultrahigh specific capacitance of 2703 F g-1 at 3 A g-1. Moreover, the asymmetric supercapacitor with this hybrid array as a positive electrode and wood-derived activated carbon as a negative electrode demonstrates high energy density (57 Wh Kg-1 at 738 W Kg-1) and very good electrochemical cycling stability.

Self-assembly of colloidal spheres and application as solvent responding polymer film.

It is the first time to fabricate and apply responsive colloidal crystal (CC) films on biocomposite material - bamboo strand board (BSB). The responsive film can be easily prepared directly through the self-assembly of soft colloidal polymer spheres containing hydrophilic monomers at ambient pressure and temperature without complicate equipment. In this approach, soft colloidal polymer spheres are synthesized by emulsion polymerization using polymerizable emulsifier. Then, the polymer latex is loaded onto the surface of BSB. The colloidal polymer spheres can directly self-assemble into a robust and transparent colloidal crystal (CC) film on BSB. Neither soft matrix nor posttreatment is needed. Compared with the traditional responsive CC, the polymer film on BSB not only had sensitive response behaviors but also had good reversibility and mechanical strength, which would provide a new method for fabrication and application of responsive CC.

Fabrication of robust crystal balls from the electrospray of soft polymer spheres/silica dispersion.

This paper presents a novel and facile approach to fabricate robust crystal balls directly through the self-assembly of soft colloidal polymer spheres by the aid of nano silica using an electrospraying technique. In this approach, soft colloidal polymer spheres are synthesized by emulsion polymerization and then blended with colloidal silica to obtain nanocomposite dispersion. When this dispersion is loaded into an injector and forced to flow through the nozzle under direct electric field, the detached droplets are collected by an oil solvent. As water and solvent evaporate, the colloidal polymer spheres and silica beads can directly self-assemble into robust crystal balls. Neither soft matrix nor post-treatment is needed. The obtained crystal balls have not only excellent mechanical properties to withstand external forces such as cutting, puckering, and bending, but also reversible deformation.