ZnO@C Coated Cellulose-Based Separators Control Lithium Deposition Direction to Stable Lithium Metal Batteries.

Li metal anodes have attracted attention due to their high specific capacity and low electrochemical potential. Nevertheless, the uncontrolled growth of Li dendrites hinders the practical application of Li metal batteries. Although the various approaches have made performance improvements, safety hazards still exist since Li dendrites are still growing along the anode to the separator during the continuous plating/stripping process. Herein, a straightforward method is proposed to achieve stable Li metal batteries with directional growth control by using a functional ZnO@C/cellulose membrane as a separator. The abundant pore structure and functional groups of biomass cellulose enhance the Li-ion transport and interface compatibility. The ZnO transforms in situ to form a Li-Zn alloy layer which is uniformly coated to the separator to direct uniform ion concentration polarization and charge distribution polarization, control the growth direction of Li, significantly improve the cycling stability, and promote the reversibility of the Li plating/exfoliation process. As a result, the symmetric cell exhibits an extreme lifetime of more than 4500 h and low polarization at 3 mA cm-2 . The cycling performance of the Li||LiFePO4 full cell reaches a capacity retention of 98% after 270 cycles at a mass loading of 10 mg cm-2 .

Mitigating Zn Dendrite Growth and Enhancing the Utilization of Zn Electrode in Aqueous Zn-Ion Batteries.

In spite of extensive research and appreciable progress, in aqueous zinc-ion batteries, Zn metal anode is struggling with low Zn utility and poor cycling stability. In this study, a 3D "electrochemical welding" composite electrode is designed by introduction of ZnO/C nanofibers film to copper foils as an anode according to pre-electrodeposition active Zn (Zn@ZnO/C-Cu). The flow of Zn2+ through carbon fiber layer is regulated by zincophilic ZnO, promoting homogeneous diffusion of Zn2+ to Cu foil. In subsequent Zn deposition/stripping processes, the hydrophobicity of ZnO/C fiber layer reduces water at the interface of Zn@ZnO/C-Cu and results in uniform electric field significant suppressing growth of Zn dendritic and side reactions. Thus, pre-electrodeposition active Zn electrochemical welds ZnO/C nanofibers and Cu foil collectively provide stable charge/electron transfer and stripping/plating of Zn with low polarization and excellent cycling performance. The assembled symmetrical batteries exhibit stable cycling performance for over 470 h under 20% utilization of Zn at 5 mA cm-2, and an average coulombic efficiency of 99.9% at low negative/positive capacity ratio (N/P = 1) after 1000 cycles in the Zn@ZnO/C-Cu||Na2V6O16·1.5H2O full cell.

Enhanced third-order nonlinear optical properties of ZnO@C-N composite microspheres.

We report the third-order nonlinear optical (NLO) properties of ZnO@C-N composite microspheres and pure ZnO which have been investigated with the Z-scan technique under continuous wave laser. ZnO@C-N composite microspheres have been hydrothermally synthesized at two different precursor concentrations to have structures at different impurity levels. Moreover, pure ZnO is prepared under the annealing process. The nonlinear optical absorption of samples was measured by using the open-aperture Z-scan technique and was evaluated relating to the two-photon absorption (TPA) mechanism. Moreover, both ZnO@C-N and ZnO microstructures exhibited a negative nonlinear refractive index (NLR) referring to the self-defocusing effect. The order of the (NLR) value, is about 10-10(cm2/W) and, the NLA coefficients of specimens are in the order of 10-5(cm/W). The NLA coefficient has a similar behavior as the NLR versus increasing incident intensity of the laser. The results show that the nonlinearity response of ZnO@C-N composites is higher than the pure ZnO and ZnO@C-N at higher precursor concentrations exhibits the maximum amount of NLA and NLR coefficients compared to other samples. This observation which is attributed to the change in optical and structural properties of material due to impurity presence, underscores the presence of impurity for engineering materials to improve the nonlinearity properties.

Hydrophilic ZnO/C nanocomposites with superior adsorption, photocatalytic, and photo-enhanced antibacterial properties for synergistic water purification.

Owing to the numerous potential applications of ZnO nanomaterials, the development of ZnO-based nanocomposites has become of great scientific interest in various fields. In this paper, we are reporting the fabrication of a series of ZnO/C nanocomposites through a simple "one-pot" calcination method under three different temperatures, 500 ℃, 600 ℃, and 700 ℃, with samples labeled as ZnO/C-500, -600, and -700, respectively. All samples exhibited adsorption capabilities and photon-activated catalytic and antibacterial properties, with the ZnO/C-700 sample showing superior performance among the three. The carbonaceous material in ZnO/C is key to expanding the optical absorption range and improving the charge separation efficiency of ZnO. The remarkable adsorption property of the ZnO/C-700 sample was demonstrated using Congo red dye, and is credited to its good hydrophilicity. It was also found to exhibit the most notable photocatalysis effect due to its high charge transfer efficiency. The hydrophilic ZnO/C-700 sample was also examined for antibacterial effects both in vitro (against Escherichia coli and Staphylococcus aureus) and in vivo (against MSRA-infected rat wound model), and it was observed to exhibit synergistic killing performance under visible-light irradiation. A possible cleaning mechanism is proposed on the basis of our experimental results. Overall, this work presents a facile way of synthesizing ZnO/C nanocomposites with outstanding adsorption, photocatalysis, and antibacterial properties for the efficient treatment of organic and bacterial contaminants in wastewater.

ZnO/C nanocomposite grafted molecularly imprinted polymers as photoelectrochemical sensing interface for ultrasensitive and selective detection of chloramphenicol.

Nanomaterials-based photoelectrochemical (PEC) detection is becoming a rapidly-developing analytical technique in chemical and biological assays due to its unique advantages of easy miniaturization, high sensitivity, and rapid turnaround time. Herein, a molecularly imprinted polymer-assisted PEC sensor based on ZnO/C nanocomposite was successfully fabricated for the highly sensitive and selective determination of chloramphenicol (CAP). Benefiting from the hydrophilic functional groups (-OH, -COOH) and large surface area of bio-templated ZnO/C nanocomposite, the tight grafting of MIP with excellent recognition ability on substrate is easier and more stable than traditional PEC sensor, thus significantly increasing the performance. Under optimal conditions, the PEC sensor exhibited significant CAP detection performance in the range of 0.01-5000 ng mL-1 with a detection LOD of 5.08 pg mL-1 (S/N = 3) and successfully applied to the detection of CAP in milk sample. Our results show that ZnO/C nanocomposite and MIP can act as an efficient photo-responsible matrix to fabricate PEC sensor, providing important application potentials for pollutants control in food and environment.

C-doped ZnO nanocomposites molecularly imprinted photoelectrochemical sensor for ultrasensitive and selective detection of oxytetracycline in milk.

Antibiotic monitoring remains vital to ensure human health and safety in the environment and foods. As the most popular detection method, photoelectrochemical (PEC) sensor can achieve rapid and accurate detection of antibiotics with the advantages of high sensitivity, easy-to-preparation process, as well as high selectivity. Herein, an extremely-efficient visible-light responsible ZnO/C nanocomposite was prepared and combined with acetylene black (as an enhanced conductive matrix), and the electron migration efficiency was greatly accelerated. Meanwhile, a molecularly imprinted polymer obtained by electrical agglomeration was conjugated as a specific recognizing site for target. Furthermore, the as-prepared rMIP-PEC sensor showed a low detection limit (8.75 pmol L-1, S/N = 3) in a wide linear detection range of 0.01-1000 nmol L-1 for oxytetracycline (OTC), with excellent selectivity and long-term stability. Our work shed light on applying C-doped ZnO semiconductor and molecularly imprinted polymer as photoelectric active sensing materials for rapid and accurate analysis of antibiotics in foods and environment.

Effective Solution toward the Issues of Zn-Based Anodes for Advanced Alkaline Ni-Zn Batteries.

Alkaline nickel-zinc (Ni-Zn) batteries, as traditional rechargeable aqueous batteries, possess an obvious advantage in terms of energy density, but their development has been hindered by the anode-concerned problems, Zn dendrites, self-corrosion, passivation, deformation, and hydrogen evolution reaction (HER). Herein, to solve these problems, a dual protective strategy is proposed toward the anode using ZnO as an initial active material, including a C coating on ZnO (ZnO@C) and a thin poly(vinyl alcohol) (PVA) layer coating on the electrode (ZnO@C-PVA). In a three-electrode configuration, the reversible capacity can reach 600 mAh g-1 for the ZnO@C-PVA. Using excessive commercial Ni(OH)2 as the cathode, the alkaline Ni-Zn cells exhibit good electrochemical performance: Discharge capacity can be as high as 640-650 mAh g-1 at 4 A g-1 with a Coulomb efficiency (CE) as high as 97-99% after activity, suggesting low self-corrosion and HER. Capacity retention is 97% after 1200 cycles, indicating rather good durability. The discharge capacity is even slightly increased with the increase of charge/discharge current density (≤8 A g-1), implying good rate performance. Additionally, the discharge voltage can reach 1.8 V (midpoint value) at various current densities, reflecting the fast reaction kinetics of the anode. Most importantly, no Zn dendrites and passivation are observed after long-term cycling. The strategy proposed here can solve the anode-concerned problems effectively, exhibiting a high application prospect.

Defect- and Interface-Induced Dielectric Loss in ZnFe2O4/ZnO/C Electromagnetic Wave Absorber.

Controlling defects and interfaces in composite absorbers can effectively regulate electromagnetic (EM) parameters and enhance the electromagnetic wave (EMW) absorption ability, but the mechanism still needs to be further elucidated. In this study, ZnFe2O4/ZnO/C composite was synthesized via the hydrothermal method followed by post-annealing in different atmospheres. Defects and interfaces were characterized by Raman, PL spectroscopy, XPS and TEM, and their relationship with dielectric loss and EMW absorption performance was discussed in detail. Results show that the N2-annealed ZnFe2O4/ZnO/C composite with abundant defects and interfaces as well as an optimized composition exhibits excellent EMW dissipation ability, with a RLmin value of -17.4 dB and an fe of 3.85 GHz at a thickness of 2.28 mm. The excellent EMW absorption performance originates from suitable impedance matching, significant conduction loss and strong dielectric loss (interfacial polarization, diploe polarization and defect polarization) dominated by lattice defects and interfaces. This study provides a view into the relationship between defects, interfaces, EM parameters and EMW absorption ability, and also suggests an effective way to promote EMW dissipation ability of the absorbers by controlling defects and interfaces.

Theoretical study on photocatalytic performance of ZnO/C2N heterostructure towards high efficiency water splitting.

The construction of van der Waals heterostructures offers effective boosting of the photocatalytic performance of two-dimensional materials. In this study, which uses the first-principles method, the electronic and absorptive properties of an emerging ZnO/C2N heterostructure are systematically explored to determine the structure's photocatalytic potential. The results demonstrate that ZnO and C2N form a type-II band alignment heterostructure with a reduced band gap, and hence superior absorption in the visible region. Furthermore, the band edge positions of a ZnO/C2N heterostructure meet the requirements for spontaneous water splitting. The ZnO/C2N heterostructure is known to possess considerably improved carrier mobility, which is advantageous in the separation and migration of carriers. The Gibbs free energy calculation confirms the high catalytic activity of the ZnO/C2N heterostructure for water-splitting reactions. All the aforementioned properties, including band gap, band edge positions, and optical absorption, can be directly tuned using biaxial lateral strain. A suitable band gap, decent band edge positions, high catalytic activity, and superior carrier mobility thus identify a ZnO/C2N heterostructure as a prominent potential photocatalyst for water splitting.

Porous magnetic carbon CoFe alloys@ZnO@C composites based on Zn/Co-based bimetallic MOF with efficient electromagnetic wave absorption.

To obtain lightweight and efficient electromagnetic wave absorbing materials, Fe2O3@ZnCo-MOF composites were prepared in this paper by in-situ growth method, and CoFe alloys@ZnO@C composites were obtained by subsequent annealing process. By varying the loading of Fe2O3 during the synthesis process, a series of composites were obtained. Among them, CoFe alloys@ZnO@C-0.1 has the best electromagnetic wave absorption performance, which can reach a reflection loss (RL) of -40.63 dB at a thickness of 2.2 mm, while the reflection loss is -44.13 dB at a thickness of 5.0 mm, and the maximum effective absorption bandwidth (EAB) is 5.84 GHz at a thickness of 2.4 mm. The excellent performance can be attributed to the synergistic effect of the dielectric and magnetic properties of the composites as well as the effective impedance matching properties. Thus, the CoFe alloys@ZnO@C composite is expected to be a lightweight and efficient material for electromagnetic wave absorption.

MOF derived ZnO/C nanocomposite with enhanced adsorption capacity and photocatalytic performance under sunlight.

In this work, ZnO/C nanocomposites were obtained by calcining the prepared metal-organic framework precursor under nitrogen. The crystallinity and structure of the prepared products were characterized by XRD, FTIR, XPS and EDS. The morphologies of samples before and after calcination were observed by FESEM. The photocatalytic performances of ZnO/C were evaluated by the degradation of methylene blue under sunlight irradiation. Combined with DRS, PL and BET, the influence of calcination temperature on photocatalytic activities of as-synthesized zinc oxide were discussed as compared with commercial zinc oxide. The results indicated that ZnO/C composite obtained at 600 °C and 700 °C exhibited the superior adsorption capacity and photocatalytic activity. The possible photocatalytic mechanism of ZnO/C nanocomposite for degradation of MB under sunlight irradiation was proposed.

Role of dissolved oxygen on the degradation mechanism of Reactive Green 19 and electricity generation in photocatalytic fuel cell.

In this study, a membraneless photocatalytic fuel cell with zinc oxide loaded carbon photoanode and platinum loaded carbon cathode was constructed to investigate the impact of dissolved oxygen on the mechanism of dye degradation and electricity generation of photocatalytic fuel cell. The photocatalytic fuel cell with high and low aeration rate, no aeration and nitrogen purged were investigated, respectively. The degradation rate of diazo dye Reactive Green 19 and the electricity generation was enhanced in photocatalytic fuel cell with higher dissolved oxygen concentration. However, the photocatalytic fuel cell was still able to perform 37% of decolorization in a slow rate (k = 0.033 h-1) under extremely low dissolved oxygen concentration (approximately 0.2 mg L-1) when nitrogen gas was introduced into the fuel cell throughout the 8 h. However, the change of the UV-Vis spectrum indicates that the intermediates of the dye could not be mineralized under insufficient dissolved oxygen level. In the aspect of electricity generation, the maximum short circuit current (0.0041 mA cm-2) and power density (0.00028 mW cm-2) of the air purged photocatalytic fuel cell was obviously higher than that with nitrogen purging (0.0015 mA cm-2 and 0.00008 mW cm-2).

Highly Cuboid-Shaped Heterobimetallic Metal-Organic Frameworks Derived from Porous Co/ZnO/C Microrods with Improved Electromagnetic Wave Absorption Capabilities.

Metal-organic framework (MOF)-derived porous metal/C composites have drawn considerable attention from the microwave absorption field owing to their large pore volumes and surface areas. Exploring single-MOF-derived materials with high intensity and broadband absorption is largely needed but remains a challenge. Here, porous Co/ZnO/C (CZC) microrods were fabricated easily from cuboid-shaped heterobimetallic MOFs. CZC provides an efficient platform for integrating different semiconductors (ZnO), magnetic metal (Co), and carbon sources into one particle, which enhances the electromagnetic (EM) wave-absorbing ability. The carbonization temperature which is critical for EM parameters was studied in detail. CZC annealed at 700 °C outperformed those obtained at 600 or 800 °C in terms of microwave wave-absorbing properties. The reflection loss (RL) was optimized to -52.6 (or -20.6) dB at 12.1 (or 14.8) GHz with an effective bandwidth (RL ≤ -10 dB) of 4.9 (or 5.8) GHz at the coating thickness of 3.0 (or 2.5) mm. Such enhancement of EM wave-absorbing capabilities is ascribed to the well-built porous structure, dielectric loss, and magnetic loss. This work offers a new way to prepare porous magnetic metal/C composites with excellent microwave-absorbing properties starting from heterobimetallic MOFs.

Three-Dimensional Hierarchical Structure ZnO@C@NiO on Carbon Cloth for Asymmetric Supercapacitor with Enhanced Cycle Stability.

In this work, we synthesized the hierarchical ZnO@C@NiO core-shell nanorods arrays (CSNAs) grown on a carbon cloth (CC) conductive substrate by a three-step method involving hydrothermal and chemical bath methods. The morphology and chemical structure of the hybrid nanoarrays were characterized in detail. The combination and formation mechanism was proposed. The conducting carbon layer between ZnO and NiO layers can efficiently enhance the electric conductivity of the integrated electrodes, and also protect the corrosion of ZnO in an alkaline solution. Compared with ZnO@NiO nanorods arrays (NAs), the NiO in CC/ZnO@C@NiO electrodes, which possess a unique multilevel core-shell nanostructure exhibits a higher specific capacity (677 C/g at 1.43 A/g) and an enhanced cycling stability (capacity remain 71% after 5000 cycles), on account of the protection of carbon layer derived from glucose. Additionally, a flexible all-solid-state supercapacitor is readily constructed by coating the PVA/KOH gel electrolyte between the ZnO@C@NiO CSNAs and commercial graphene. The energy density of this all-solid-state device decreases from 35.7 to 16.0 Wh/kg as the power density increases from 380.9 to 2704.2 W/kg with an excellent cycling stability (87.5% of the initial capacitance after 10000 cycles). Thereby, the CC/ ZnO@C@NiO CSNAs of three-dimensional hierarchical structure is promising electrode materials for flexible all-solid-state supercapacitors.

ZnO-Assisted Growth of CH3NH3PbI3- xCl x Film and Efficient Planar Perovskite Solar Cells with a TiO2/ZnO/C60 Electron Transport Trilayer.

Appropriate electron transport layers (ETL) are essential in perovskite solar cells (PSCs) with high power conversion efficiency (PCE). Herein, a TiO2/ZnO/C60 trilayer fabricated on a transparent fluorine-doped tin oxide (FTO) glass substrate is used as a compound ETL in planar PSCs. The trilayer shows positive effects on both perovskite synthesis and device performance. The ZnO layer assists growth of CH3NH3PbI3- xCl x ( x ≈ 0) annealed at a lower temperature and with a shorter time, which is due to a more rapid and easier decomposition of the intermediate CH3NH3PbCl3 phase in the growth of CH3NH3PbI3- xCl x. All three materials in the trilayer are important for obtaining PSCs with a high PCE. ZnO is critical for enhancing the open circuit voltage by ensuring proper energy alignment with the TiO2 and C60 layers. C60 enhances carrier extraction from the CH3NH3PbI3- xCl x layer. TiO2 eliminates charge recombination at the FTO surface and ensures efficient electron collection. The best-performing PSC based on the TiO2/ZnO/C60 electron transport trilayer features a PCE of 18.63% with a fill factor of 79.12%. These findings help develop an understanding of the effects of ZnO-containing ETLs on perovskite film synthesis and show promise for the future development of high-performance PSCs with compound ETLs.

High-performance and ultra-stable lithium-ion batteries based on MOF-derived ZnO@ZnO quantum dots/C core-shell nanorod arrays on a carbon cloth anode.

MOF-derived ZnO@ZnO Quantum Dots/C core-shell nanorod arrays grown on flexible carbon cloth are successfully fabricated as a binder-free anode for Li-ion storage. In combination with the advantages from the ZnO/C core-shell architecture and the 3D nanorod arrays, this material satisfies both efficient ion and fast electron transport, and thus shows superior rate capability and excellent cycling stability.