Output Enhancement of Triboelectric Nanogenerators Based on Hierarchically Regular Cadmium Coordination Polymers for Photocycloaddition.

Exploiting the well-arranged and tunable frameworks of crystalline materials, we herein report coordination polymers (CPs) with modulated hierarchical structures as triboelectric materials to construct and extend the application scope of triboelectric nanogenerators (TENGs). Different lengths and shapes of bridging ligands [4,4'-bpa = 1,2-bis(4-pyridyl)ethane, 4,4'-bpe = 1,2-bis(4-pyridyl)ethene, and 4,4'-bpp = 1,3-di(2-pyridyl)propane for 1, 2, and 3, respectively] were used to construct Cd-CP-based hierarchical frameworks. These compounds were used as triboelectric materials, and their electronic structure contributions were determined by the output of the corresponding TENGs. The results indicated that 2-TENG with the 4,4'-bpe ligand had the highest output, attributed to the improvement in the electron activity due to the π-conjugation group in the bridging ligand, which was further verified by density functional theory calculations. Furthermore, 2@PVDF (PVDF = polyvinylidene fluoride) composite films with different concentrations of Cd-CP were prepared. Detailed electrical characterizations revealed that the arrangement of 12% active constituents of Cd-CP-2 effectively enhanced the output performance of 2@PVDF-TENG, which could light up an ultraviolet lamp plate to successfully execute the [2 + 2] photocycloaddition.

Metal-Ion Coupling in Metal-Organic Framework Materials Regulating the Output Performance of a Triboelectric Nanogenerator.

Metal-organic frameworks (MOFs) as friction nanopower generation materials have attracted more and more research and attention because of the inherent three-dimensional framework structure and large aperture. In this work, the ZUT-75(Mn) with a one-dimensional pore structure was synthesized by using electron-rich benzimidazole carboxylic acid ligands, and isomorphic offspring MOF materials were obtained by single crystal-single crystal solvent-assisted metal-ion exchange. The exchange process was monitored by liquid UV-vis spectroscopy, atomic absorption spectrometry, and energy-dispersive X-ray spectroscopy. The metal-oxygen coordination energy, X-ray photoelectron spectroscopy binding energy, and hard-soft acid-base principle verified the spontaneity of the central-metal-exchange reaction. The four materials were applied to a triboelectric nanogenerator (TENG), and the output performance law of ZUT-75 was Co-MT > Zn-MT > Cu-MT > Mn-MT. Among them, the charge and power densities of Co-MT were up to 127.05 µC m-2 and 3280.50 mW m-2. When the density functional theory calculation and variable-temperature magnetic susceptibility test results were combined, it was concluded that low metal-ion-coupling degree promoted the formation and transfer of contact electrifications, which greatly improved the output performance of the TENG. This work provided a new idea for improving the output performance of the TENG.

Covalent Organic Frameworks with Tailored Functionalities for Modulating Surface Potentials in Triboelectric Nanogenerators.

Designing materials with high triboelectric is an efficient way of improving output performance of triboelectric nanogenerators (TENGs). Herein, we synthesized a series of covalent organic frameworks (COFs) with similar skeletons but various functional groups ranging between electron-donating and electron-withdrawing. These COFs form an ideal platform for clarifying the contribution of each group to TENG performance because the pore wall is perturbed in a predesigned manner. Kelvin probe force microscopy and computational data suggest that surface potentials and electron affinities of COFs can be improved by introducing electron-donating or withdrawing groups, with the highest values observed for fluorinated COF. The TENG with fluorinated COF delivered an output voltage and current of 420 V and 64 µA, respectively, which are comparable to other reported materials. This strategy can be used to efficiently screen suitable frameworks as TENG materials with excellent output performance.

Programmable Triboelectric Nanogenerators Dependent on the Secondary Building Units in Cadmium Coordination Polymers.

Precisely controlling the coordination microenvironment and electronic features of polynuclear secondary building units (SBUs) in coordination polymers (CPs) is an efficient approach to governing their fundamental performance. Here, different multinuclear SBUs (binuclear, trinuclear, and pentanuclear SBUs for 1-3, respectively) were introduced into Cd-based CPs, which were used as frictional electrode materials, to clarify the contributions of polynuclear Cd-SBUs through the output of triboelectric nanogenerators (TENGs). The results demonstrated that 1-TENG with binuclear Cd-SBUs possessed the highest output, whereas 3-TENG with the pentanuclear Cd-SBUs indicated the minimum output, suggesting that the binuclear Cd-SBUs in 1 lost electrons most readily and generated much more charge, which was further confirmed by density functional theory calculations. This work opened a new prospect to confirm the gaining/losing capability of polynuclear Cd-SBUs in CPs and provided an effective approach to tuning both the stability and functionality of polynuclear CPs as frictional pair materials to regulate the output of CPs-based TENGs.

Organosulfonate Counteranions-A Trapped Coordination Polymer as a High-Output Triboelectric Nanogenerator Material for Self-Powered Anticorrosion.

Selection of the friction electrode materials is crucial to the performance of a triboelectric nanogenerator (TENG). In the present study, a metal-organic coordination complex containing organosulfonate counteranions with electron-donating ability was synthesized through the coordination-driven self-assembly approach under mild reaction conditions and was chosen as a positive electrode material to construct a triboelectric nanogenerator, exhibiting high-output performance with a peak value of short circuit current density of 98.6 µA and an output voltage of 1180 V. As a practical application, it was shown to light up 1488 commercial green LEDs and power an anticorrosion system device to protect metals from corrosion.

Bromine-Functionalized Covalent Organic Frameworks for Efficient Triboelectric Nanogenerator.

Covalent organic frameworks (COFs) enable precise integration of various organic building blocks into porous skeletons through topology predesign. Here, we report the first example of COFs by integrating electron withdrawing bromine group onto the skeletons for triboelectric nanogenerators (TENG). The resulting framework exhibits high surface area and good crystallinity. Thus, the bromine functionalized COF has more regular aligned π columns and arrays over the skeleton than bare COFs, which in turn significantly enhances charge transport ability. As a result, bromine functionalized COFs showed higher electrical output performance at 5 Hz with a peak value of short circuit current density of 43.6 µA and output voltage of 416 V, which is 2 and 1.3 times higher than those of bare COFs (21.6 µA and 318 V), respectively. These results demonstrated that this strategy for engineering electron withdrawing groups on the skeleton could open a new aspect of COFs for developing TENG devices.

Cream roll-inspired advanced MnS/C composite for sodium-ion batteries: encapsulating MnS cream into hollow N,S-co-doped carbon rolls.

With advantages of high theoretical capacity and low cost, manganese sulfide (MnS) has become a potential electrode material for sodium-ion batteries (SIBs). However, complicated preparations and limited cycle life still hinder its application. Inspired by cream rolls in our daily life, a MnS/N,S-co-doped carbon tube (MnS/NSCT) composite with a 3D cross-linked tubular structure is prepared via an ultra-simple and low-cost method in this work. As the anode for SIBs, the cream roll-like MnS/NSCT composite has delivered the best electrochemical performance to date (the highest capacity of 550.6 mA h g-1 at 100 mA g-1, the highest capacity of 447.0 mA h g-1 after 1400 cycles at 1000 mA g-1, and the best rate performance of 319.8 mA h g-1 at 10 000 mA g-1). Besides, according to several in situ and ex situ techniques, the sodium storage mechanism of MnS/NSCTs is mainly from a conversion reaction, and the superior electrochemical performance of MnS/NSCTs is mainly attributed to the unique cream roll-like structure. More importantly, this simple method may be feasible for other anode materials, which will greatly promote the development of SIBs.

Bi-component synergic effect in lily-like CdS/Cu7S4 QDs for dye degradation.

CdS has attracted extensive attention in the photocatalytic degradation of wastewater due to its relatively narrow bandgap and various microstructures. Previous reports have focused on CdS coupled with other semiconductors to reduce the photocorrosion and improve the photocatalytic performance. Herein, a 3D hierarchical CdS/Cu7S4 nanostructure was synthesized by cation exchange using lily-like CdS as template. The heterojunction material completely inherits the special skeleton of the template material and optimizes the nano-scale morphology, and achieves the transformation from nanometer structure to quantum dots (QDs). The introduction of Cu ions not only tuned the band gap of the composites to promote the utilization of solar photons, more importantly, Fenton-like catalysis was combined into the degradation process. Compared with the experiments of organic dye degradation under different illumination conditions, the degradability of the CdS/Cu7S4 QDs is greatly superior to pure CdS. Therefore, the constructed CdS/Cu7S4 QDs further realized the optimization of degradation performance by the synergic effect of photo-catalysis and Fenton-like catalysis.

Anti-corrosion of amphoteric metal enhanced by MAO/corrosion inhibitor composite in acid, alkaline and salt solutions.

An anticorrosive composite coating with enhanced corrosion resistance in acid, alkaline and salt solutions was fabricated by compounding micro- and nanoporous inorganic structure and organic corrosion inhibitor, which was used to improve the corrosion resistance of amphoteric metal and its oxides in various corrosive medium. Micro- and nanoporous structure was prepared by microarc oxidation (MAO) coatings on 2024 aluminium alloy, which was used both as the inorganic anticorrosion coating and the container for organic corrosion inhibitor (M16). Electrochemical impedance spectroscopy, Tafel plots and salt spray resistance were measured to research the anticorrosion performance of the MAO/M16 composite coating. Enhanced corrosion resistance was observed for the MAO/M16 coating compared to the MAO by itself. When the concentration of corrosion inhibitor M16 is at 2 w%, the best anticorrosive properties of the composite coating were obtained. Moreover, the MAO/M16 composite coating showed better corrosion-resistant performance than pure MAO coating and Al alloy substrate in the corrosion environment of 1 M HCl, 0.1 M NaOH and 3.5 w% NaCl solutions, respectively. The enhancement of corrosion resistance for MAO/M16 composite coating was achieved by a unique synergy between the microarc oxidation layer and the corrosion inhibitor. The composite coating indicates its promising applications in acid, alkaline and salt solutions environments and other harsh environments.

Hollow hematite single crystals deposited with ultra-thin Al2O3 by atom layer deposition for improved photoelectrochemical performance.

Hematite (α-Fe2O3) is a red material with a band gap of about 2.0 eV, which indicates that it can absorb more solar light. It is a promising photocatalyst applied in many fields. In this paper, α-Fe2O3 single crystal hollow hexagonal bipyramids were synthesized by a simple one-pot hydrothermal method. The morphology and structure of the prepared α-Fe2O3 hollow hexagonal bipyramids were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The hollow single crystals show a good light absorption and performance in photodegradation of methylene blue (MB). Due to the strategy of depositing ultra-thin layers of Al2O3 by atomic layer deposition (ALD), the photoelectrochemical (PEC) performance of α-Fe2O3 under the simulated solar light irradiation is also improved.

Conducting polymer PPy nanowire-based triboelectric nanogenerator and its application for self-powered electrochemical cathodic protection.

As a new type of energy harvesting device, the triboelectric nanogenerator (TENG) can convert almost all kinds of mechanical energy into electricity based on the coupling of triboelectrification and electrostatic induction. Here, a novel TENG is constructed with a conducting polymer polypyrrole nanowire (PPy NW) electrode, which is prepared by an electrochemical polymerization method with anodic aluminum oxide (AAO) as the template. The PPy NW-based TENG shows high output performance with a maximum short circuit current density of 23.4 mA m-2 and output voltage of 351 V, which can light 372 commercial red LEDs. Moreover, a self-powered anticorrosion system powered by the PPy NW-based TENG is designed, which can provide extra electrons to inject into the surface of the protected metals, forming effective impressed current cathodic protection by harvesting mechanical energy or wind energy. This smart device has potential applications for protecting metals from corrosion in daily life, industrial production and ocean exploration by harvesting the energies in the ambient environment.

Surface engineering for an enhanced photoelectrochemical response of TiO2 nanotube arrays by simple surface air plasma treatment.

A simple method to improve the photoelectrochemical performance of TiO2 nanotube arrays (NTs) by simple air plasma post-treatment is reported. The air plasma treated sample shows higher photocurrent density and incident photo current efficiency with high stability, about 3-4 times that of the pristine TiO2 NTs even after six months.