Enhanced Active Sites and Stability in Nano-MOFs for Electrochemical Energy Storage through Dual Regulation by Tannic Acid

Ultrathin layer TAFC on BiVO4 with ligand-to-metal charge transfer enhances built-in electric field for boosting photoelectrochemical water oxidation

To reveal the mechanism of charge transfer between interfaces of BiVO4-based heterogeneous materials in photoelectrochemical water splitting system, the cocatalyst was grown in situ using tannic acid (TA) as a ligand and Fe and Co ions as metal centers (TAFC), and then uniformly and ultra-thinly coated on BiVO4 to form photoanodes. The results show that the BiVO4/TAFC achieves a superior photocurrent density (4.97 mA cm-2 at 1.23 VRHE). The charge separation and charge injection efficiencies were also significantly higher, 82.0 % and 78.9 %, respectively. From XPS, UPS, KPFM, and density functional theory calculations, Ligand-to-metal charge transfer (LMCT) acts as an electron transport highway in TAFC ultrathin layer to promote the concentration of electrons towards metal center, leading to an increase in the work function, which enhances the built-in electric field and further improves the charge transport. This study demonstrated that the LMCT pathway on TA-metal complexes enhances the built-in electric field in BiVO4/TAFC to promote charge transport and thus enhance water oxidation, providing a new understanding of the performance improvement mechanism for the surface-modified composite photoanodes.

Cellulose-based biomass composite films for plastic replacement: Synergistic UV shielding, antibacterial and antioxidant properties

With the gradual increase in environmental awareness and the growing demand for food safety, sustainable and environmentally friendly cellulose-based materials have become a promising alternative to petroleum-based plastics. However, in practice, packaging materials prepared from cellulose-based materials still have some unsatisfactory properties, such as monofunctionality, low transparency, and lack of UV shielding, antibacterial or antioxidant properties. Herein, a novel synthetic strategy is proposed in this paper, specifically, tannic acid (TA), a green natural extract with antibacterial and antioxidant properties, is used as a plasticizer and cross-linker, and oxidized cellulose nanocellulose (TOCN) modified with folic acid (FA) grafting is blended with TA, and cellulose-based biomass thin films with ultraviolet (UV) shielding, antibacterial, and antioxidant properties have been successfully prepared by using a simple vacuum-assisted filtration. The experimental results showed that the films could completely block ultraviolet light at wavelengths of 200-400 nm while providing 81.47 % transparency in the visible spectrum, while the introduction of TA conferred excellent antibacterial and antioxidant capabilities with antioxidant activity of up to 95 %, and also resulted in films with excellent mechanical properties. Therefore, this work provides ideas for the design and manufacture of competitive biomass green packaging materials, laying the foundation for future applications in food packaging.

Tailoring the Electrochemical Responses of MOF-74 Via Dual-Defect Engineering for Superior Energy Storage

Rationally designed defects in a crystal can confer unique properties. This study showcases a novel dual-defects engineering strategy to tailor the electrochemical response of metal-organic framework (MOF) materials used for electrochemical energy storage. Salicylic acid (SA) is identified as an effective modulator to control MOF-74 growth and induce structural defects, and cobalt cation doping is adopted for introducing a second type of defect. The resulting dual-defects engineered bimetallic MOF exhibits a discharging capacity of 218.6 mAh g-1, 4.4 times that of the pristine MOF-74, and significantly improved cycling stability. Moreover, the engineered MOF-74(Ni0.675Co0.325)-8//Zn aqueous battery shows top energy/power density performances for Ni-Zn batteries (266.5 Wh kg-1, 17.22 kW kg-1). Comprehensive investigations reveal that engineered defects modify the local coordination environment and promote the in situ electrochemical reconfiguration during operation to significantly boost the electrochemical activity. This work suggests that rational tailoring of the defects within the MOF crystal is an effective strategy to manipulate the coordination environment of the metal centers and the corresponding electrochemical reconfiguration for electrochemical applications.

Advanced High-Energy All-Solid-State Hybrid Supercapacitor with Nickel-Cobalt-Layered Double Hydroxide Nanoflowers Supported on Jute Stick-Derived Activated Carbon Nanosheets

Developing efficient, lightweight, and durable all-solid-state supercapacitors is crucial for future energy storage systems. The study focuses on optimizing electrode materials to achieve high capacitance and stability. This study introduces a novel two-step pyrolysis process to synthesize activated carbon nanosheets from jute sticks (JAC), resulting in an optimized JAC-2 material with a high yield (≈24%) and specific surface area (≈2600 m2 g-1). Furthermore, an innovative in situ synthesis approach is employed to synthesize hybrid nanocomposites (NiCoLDH-1@JAC-2) by integrating JAC nanosheets with nickel-cobalt-layered double hydroxide nanoflowers (NiCoLDH). These nanocomposites serve as positive electrode materials and JAC-2 as the negative electrode material in all-solid-state asymmetric hybrid supercapacitors (HSCs), exhibiting remarkable performance metrics. The HSCs achieve a specific capacitance of 750 F g-1, a specific capacity of 209 mAh g-1 (at 0.5 A g-1), and an energy density of 100 Wh kg-1 (at 250 W kg-1) using PVA/KOH solid electrolyte, while maintaining outstanding cyclic stability. Importantly, a density functional theory framework is utilized to validate the experimental findings, underscoring the potential of this novel approach for enhancing HSC performance and enabling the large-scale production of transition metal-based layered double hydroxides.

Gallic acid-loaded HFZIF-8 for tumor-targeted delivery and thermal-catalytic therapy

"Transition" metal-coordinated plant polyphenols are a type of promising antitumor nanodrugs owing to their high biosafety and catalytic therapy potency; however, the major obstacle restricting their clinical application is their poor tumor accumulation. Herein, Fe-doped ZIF-8 was tailored using tannic acid (TA) into a hollow mesoporous nanocarrier for gallic acid (GA) loading. After hyaluronic acid (HA) modification, the developed nanosystem of HFZIF-8/GA@HA was used for the targeted delivery of Fe ions and GA, thereby intratumorally achieving the synthesis of an Fe-GA coordinated complex. The TA-etching strategy facilitated the development of a cavitary structure and abundant coordination sites of ZIF-8, thus ensuring an ideal loading efficacy of GA (23.4 wt%). When HFZIF-8/GA@HA accumulates in the tumor microenvironment (TME), the framework is broken due to the competitive protonation ability of overexpressed protons in the TME. Interestingly, the intratumoral degradation of HFZIF-8/GA@HA provides the opportunity for the in situ "meeting" of GA and Fe ions, and through the coordination of polyhydroxyls assisted by conjugated electrons on the benzene ring, highly stable Fe-GA nanochelates are formed. Significantly, owing to the electron delocalization effect of GA, intratumorally coordinated Fe-GA could efficiently absorb second near-infrared (NIR-II, 1064 nm) laser irradiation and transfer it into thermal energy with a conversion efficiency of 36.7%. The photothermal performance could speed up the Fenton reaction rate of Fe-GA with endogenous H2O2 for generating more hydroxyl radicals, thus realizing thermally enhanced chemodynamic therapy. Overall, our research findings demonstrate that HFZIF-8/GA@HA has potential as a safe and efficient anticancer nanodrug.

Unlatching the Additional Zinc Storage Ability of Vanadium Nitride Nanocrystallites

Vanadium-based materials, due to their diverse valence states and open-framework lattice, are promising cathodes for aqueous zinc ion batteries (AZIBs), but encounters the major challenges of in situ electrochemical activation process, potent polarity of the aqueous electrolyte and periodic expansion/contraction for efficient Zn2+ storage. Herein, architecting vanadium nitride (VN) nanosheets over titanium-based hollow nanoarrays skeletal host (denoted VNTONC) can simultaneously modulate address those challenges by creating multiple interfaces and maintaining the (1 1 1) phase of VN, which optimizes the Zn2+ storage and the stability of VN. Benefiting from the modulated crystalline thermodynamics during the electrochemical activation of VN, two outcomes are achieved; I) the cathode transforms into a nanocrystalline structure with increased active sites and higher conductivity and; II) a significant portion of the (1 1 1) crystal facets is retained in the process leading to the additional Zn2+ storage capacity. As a result, the as-prepared VNTONC electrode demonstrates remarkable discharge capacities of 802.5 and 331.8 mAh g-1 @ 0.5 and 6.0 A g-1 , respectively, due to the enhanced kinetics as validated by theoretical calculations. The assembled VNTONC||Zn flexible ZIB demonstrates excellent Zn storage properties up to 405.6 mAh g-1 , and remarkable robustness against extreme operating conditions.

Insights into Nano- and Micro-Structured Scaffolds for Advanced Electrochemical Energy Storage

Adopting a nano- and micro-structuring approach to fully unleashing the genuine potential of electrode active material benefits in-depth understandings and research progress toward higher energy density electrochemical energy storage devices at all technology readiness levels. Due to various challenging issues, especially limited stability, nano- and micro-structured (NMS) electrodes undergo fast electrochemical performance degradation. The emerging NMS scaffold design is a pivotal aspect of many electrodes as it endows them with both robustness and electrochemical performance enhancement, even though it only occupies complementary and facilitating components for the main mechanism. However, extensive efforts are urgently needed toward optimizing the stereoscopic geometrical design of NMS scaffolds to minimize the volume ratio and maximize their functionality to fulfill the ever-increasing dependency and desire for energy power source supplies. This review will aim at highlighting these NMS scaffold design strategies, summarizing their corresponding strengths and challenges, and thereby outlining the potential solutions to resolve these challenges, design principles, and key perspectives for future research in this field. Therefore, this review will be one of the earliest reviews from this viewpoint.

Synergistic Effect of Oxygen Vacancy and High Porosity of Nano MIL-125(Ti) for Enhanced Photocatalytic Nitrogen Fixation

This work reports that a low-temperature thermal calcination strategy was adopted to modulate the electronic structure and attain an abundance of surface-active sites while maintaining the crystal morphology. All the experiments demonstrate that the new photocatalyst nano MIL-125(Ti)-250 obtained by thermal calcination strategy has abundant Ti3+ induced by oxygen vacancies and high specific surface area. This facilitates the adsorption and activation of N2 molecules on the active sites in the photocatalytic nitrogen fixation. The photocatalytic NH3 yield over MIL-125(Ti)-250 is enhanced to 156.9 μmol g-1  h-1 , over twice higher than that of the parent MIL-125(Ti) (76.2 μmol g-1  h-1 ). Combined with density function theory (DFT), it shows that the N2 adsorption pattern on the active sites tends to be from "end-on" to "side-on" mode, which is thermodynamically favourable. Moreover, the electrochemical tests demonstrate that the high atomic ratio of Ti3+ /Ti4+ can enhance carrier separation, which also promotes the efficiency of photocatalytic N2 fixation. This work may offer new insights into the design of innovative photocatalysts for various chemical reduction reactions.

Expediting Ethylbenzene Oxidation via a Bimetallic Cobalt-Manganese Spinel Structure with a Modulated Electronic Environment

The catalytic oxidation of ethylbenzene (EB) into acetophenone (AP) is a vibrant area, with a growing number of researchers paying attention to this thematic investigation. Herein, we demonstrate that spinel-type (Co,Mn)(Co,Mn)2O4 can function as an efficient catalyst for the solvent-free oxidation of EB with molecular oxygen. The incorporation of Mn into the Co3O4 network can break the local structural symmetry of Co-O-Co linkages due to the bond competition, inducing the formation of an asymmetrical Co-O-Mn configuration with an electron local exchange interaction. The Co-O-Mn sites can facilitate the perturbation of nonpolar O2 and thus contribute to the generation of abundant •O2- species for initiating the oxidation of EB. We envision that this study not only provides a promising catalyst for EB oxidation but also affords a new insight into the design of advanced spinel oxides for selective oxidation reactions.