The sluggish kinetics of the oxygen evolution reaction (OER) severely limit the efficiency of water electrolysis, rendering the urea oxidation reaction (UOR) an attractive alternative for sustainable hydrogen production. To address this issue, a NiFe layered double hydroxide (LDH) on nickel foam (NF) is sequentially subjected to Mo doping and in situ partial sulfurization, yielding a Mo-NiFe LDH/NiFeS/NF composite. The synergy between Mo incorporation and the resulting LDH/sulfide heterointerface modulates the electronic structure of the active sites, optimizes the adsorption energetics of reaction intermediates, and thus promotes both the UOR and hydrogen evolution reaction (HER). The Mo-NiFe LDH/NiFeS/NF catalyst requires only 1.467 V to deliver 100 mA cm -2 for UOR, substantially outperforming conventional OER catalysts. When employed as both the anode and cathode in a two-electrode urea electrolysis cell, it achieves 100 mA cm -2 at a cell voltage of 1.861 V, with stable operation exceeding 50 h. This work demonstrates a scalable strategy for constructing high-performance bifunctional electrocatalysts toward energy-efficient hydrogen production via UOR-assisted water electrolysis.
FeNi layered double hydroxides (LDHs) have attracted considerable interest as peroxidase-like nanozymes owing to their tunable bimetallic composition, abundant metal active sites, and structurally designable layered architectures. In this study, a series of FeNi LDH nanozymes with different Fe/Ni feeding ratios were constructed using MIL-88A as both a sacrificial template and an Fe source. The effects of Fe/Ni ratio on surface growth behavior, H 2 O 2 activation capability, and glutathione (GSH) colorimetric sensing performance were systematically investigated. The results show that the Fe/Ni ratio plays a critical role in regulating LDH growth on the MIL-88A-derived framework. With increasing Ni content, the surface morphology gradually evolves from particulate coverage to a nanosheet-dominated architecture. Among the prepared samples, FeNi 2 -LDH achieves an optimal balance among structural integrity, nanosheet uniformity, porous features, and accessible Fe-Ni synergistic sites, thereby exhibiting the highest peroxidase-like activity. Steady-state kinetic analysis and ESR measurements further reveal that FeNi 2 -LDH possesses favorable apparent affinity toward H2O2 and enhanced ·OH generation capability, which efficiently promotes TMB oxidation. Based on the FeNi 2 -LDH-TMB-H 2 O 2 chromogenic system, sensitive colorimetric detection of GSH was achieved with a linear range of 1-30 μM and a detection limit of 0.8 μM. This work provides a useful strategy for enhancing the catalytic performance of LDH-based nanozymes through bimetallic ratio engineering and offers a feasible platform for the colorimetric detection of reductive biomolecules.
Near-infrared (NIR) light is of great importance for radar, stealth, and imaging applications. However, the polarization state of NIR light cannot be directly perceived by the naked eye, posing challenges for practical detection. Here, we demonstrate a strategy for visualizing NIR polarization states by integrating a reflective metasurface with NaYF 4 : Yb 3+ /Tm 3+ upconversion nanoparticles (UCNPs). The metasurface is designed with a polarization-dependent phase profile that generates two split fluorescence ring patterns under 980 nm excitation. By analyzing the intensity ratio between the two rings, the ellipticity and handedness of the incident polarization can be determined intuitively. Experimental results agree well with far-field diffraction simulations, confirming the feasibility of this approach. Our work provides a new route toward compact and visual NIR polarimetry using rare-earth-doped UCNPs and metasurfaces.
Exploiting a facile and efficient, route for energetic arrays is of critical importance for boosting their energy output and broadening their application prospects. In this work, Cu(BTA) energetic arrays were successfully fabricated on copper substrates via an electrochemical confinement growth method, based on the coordination reaction between Cu(OH) 2 arrays and energetic ligands. The chemical composition, microscopic morphology, thermal behaviors and ignition characteristics of the samples were systematically characterized by scanning electron microscopy, infrared spectroscopy, differential scanning calorimetry and pulsed laser ignition tests. The results demonstrate that the Cu(BTA) energetic arrays synthesized via coordination reaction between Cu(OH) 2 arrays and H 2 bta ligands consist of nanorods with an average length of 4310 nm and an average width of 330 nm, and their morphological features on copper substrates can be finely tuned by adjusting reaction parameters, including reaction time, solution concentration, and applied voltage. Thermal analysis reveals that the arrays presents a onset thermal decomposition temperature of 226.39 °C with a heat release of 737.05 J·g -1 , demonstrating favorable thermal energetic performance. Furthermore, ignition characterization confirms that the arrays achieves a flame height of 16.51 mm and a combustion duration of 700 μs, indicating excellent ignition reactivity. In conclusion,this work offers experimental support for the fabrication of energetic arrays and their practical applications in igniters and other related fields.
Layered double hydroxides (LDHs) show considerable potential as pseudocapacitive materials for supercapacitors; however, their electrical conductivity and cycling stability remain critical challenges for enhancing overall performance. In this study, pure CoFe-LDH and its composite series with activated carbon (AC) were successfully fabricated on nickel foam substrates via a hydrothermal method. The effects of AC addition on the microstructure and electrochemical behavior of the materials were systematically investigated using characterization techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results demonstrate that the composite material CoFe-LDH/AC[Formula: see text], prepared with an AC dosage of 15[Formula: see text]mg, exhibits the most outstanding energy storage performance: a specific capacitance of 3993 Fg[Formula: see text] at a current density of 1 Ag[Formula: see text], representing a 47.2% improvement compared with pure CoFe-LDH (2713 Fg[Formula: see text]); furthermore, the capacity retention remains at 77.9% even at a high current density of 10 Ag[Formula: see text], indicating excellent rate capability. The cycling durability test shows that the electrode material retains 42% of its initial capacitance after 5000 charge/discharge cycles at a current density of 5 Ag[Formula: see text]. This study confirms that the synergistic enhancement between AC and CoFe-LDH significantly improves the electrical conductivity and structural stability of the composite materials, effectively boosting the overall electrochemical performance, which holds important significance for the development of high-performance supercapacitor electrode materials.
