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.

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.

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.