HMT-Controlled Synthesis of Mesoporous NiO Hierarchical Nanostructures and Their Catalytic Role towards the Thermal Decomposition of Ammonium Perchlorate

Enhanced voltage and capacitance in flexible supercapacitors using electrospun nanofiber electrolytes and CuNi2O3@N-Doped omnichannel carbon electrodes

Developing functional solid polymer electrolytes (SPEs) is crucial for flexible, lightweight, and portable supercapacitors. This work presents an electrospinning approach to fabricate SPEs using poly(vinyl alcohol)-sodium chloride (PVA-NaCl) nanofibers (PNNF). CuNi2O3 nanoparticles deposited on nitrogen-doped omnichannel carbon nanofibers (CuNi2O3@N-OCCFs), coated onto a carbon cloth (CC), serve as the positive electrode, enhancing faradaic capacitance. Meanwhile, the rationally designed N-OCCFs, also coated onto CC, function as the negative electrode, providing a high-surface-area, and facilitating rapid electron transport. Comprehensive characterization revealed insights into the morphology and chemical composition of both electrodes and the PNNF electrolyte. An all-solid-state asymmetric flexible supercapacitor (AFSC) device, CuNi2O3@N-OCCFs-1.5//N-OCCFs-1.5, was assembled using PNNF as both the electrolyte and separator and evaluated against devices employing gel and aqueous electrolytes. The PNNF electrolyte enabled a wider potential window (2.2 V) compared to gel (2.0 V) and liquid (1.8 V) electrolytes. The AFSC achieved an impressive energy density of 63.6 Wh kg-1 at a power density of 1100 W kg-1, with 96.2% capacitance retention after 6000 charge/discharge cycles at 10 A g⁻1. When two devices were connected in series, they powered a red LED for 5.33 min and a blue LED for 1.43 min, demonstrating practical applicability. This study provides a simple and effective strategy for fabricating high-energy-density AFSCs with excellent cycling stability and broad potential for flexible electronics.

Modeling adsorption reactions of ammonium perchlorate on rutile and anatase surfaces

In this work, the effects of two TiO2 polymorphs on the decomposition of ammonium perchlorate (NH4ClO4) were studied experimentally and theoretically. The interactions between AP and various surfaces of TiO2 were modeled using density functional theory (DFT) calculations. Specifically, the adsorption of AP on three rutile surfaces (1 1 0), (1 0 0), and (0 0 1), as well as two anatase surfaces (1 0 1), and (0 0 1) were modeled using cluster models, along with the decomposition of adsorbed AP into small molecules. The optimized complexes of the AP molecule on TiO2 surfaces were very stable, indicating strong covalent and hydrogen bonding interactions, leading to highly energetic adsorption reactions. The calculated energy of adsorption (ΔEads) ranged from -120.23 to -301.98 kJ/mol, with highly exergonic calculated Gibbs free energy (ΔGads) of reaction, and highly exothermic enthalpy of reaction (ΔHads). The decomposition of adsorbed AP was also found to have very negative ΔEdec values between -199.08 and -380.73 kJ/mol. The values of ΔGdec and ΔHdec reveal exergonic and exothermic reactions. The adsorption of AP on TiO2 surfaces anticipates the heat release of decomposition, in agreement with experimental results. The most common anatase surface, (1 0 1), was predicted to be more reactive for AP decomposition than the most stable rutile surface, (1 1 0), which was confirmed by experiments. DFT calculations show the mechanism for activation of the two TiO2 polymorphs is entropy driven.

Microwave absorption property of GO-Fe/FeO-NiO HNFs: GO decorated Fe/FeO-NiO hexagonal flakes with a 2D/0D/2D structure

In this study, Fe/FeO-NiO HNFs in which 2D NiO hexagonal nanoflakes (NiO HNFs) were decorated by 0D Fe/FeO NPs were prepared by a facile hydrothermal method. Then, 0D/2D Fe/FeO-NiO HNFs were loaded on 2D GO sheets in three different weight ratios of GO (1 : 3), (1 : 4), and (1 : 5) to Fe/FeO-NiO HNFs and a novel GO-Fe/FeO-NiO HNF composite with a 2D/0D/2D structure was successfully produced. TEM images revealed the interesting morphology of the GO-Fe/FeO-NiO HNF composite in which individual FeO NPs with a narrow size distribution (∼15 nm) were arranged in hexagonal NiO nanoflakes, decorated on the GO substrate. Since the morphology of nanomaterials has an important effect on their microwave absorption properties, designing a composite with an asymmetric morphology, which is the combination of zero, one, and two-dimensional nanostructures can be very efficient for adjusting the microwave absorption property. The microwave absorption ability of GO-Fe/FeO-NiO HNF composites was surveyed. All samples of Fe/FeO-NiO HNF composites exhibited superior microwave attenuation performance in terms of reflection loss with a suitable bandwidth. The minimum reflection losses for GO-Fe/FeO-NiO HNFs (1 : 3), (1 : 4), and (1 : 5) reached -75.22, -53, and -18 dB, respectively, and the effective absorption bandwidths (RL ≤ -10 dB) for GO-Fe/FeO-NiO HNFs (1 : 3), (1 : 4), and (1 : 5) were 2, 3 and 3.2 GHz, respectively.

Self-templating hydrothermal synthesis of carbon-confined double-shelled Ni/NiO hollow microspheres for diphenylamine detection in fruit samples

Toxic substances, such as heavy metals, toxins, pesticides, pathogens, and veterinary drug residues in food are hazardous to consumer health. The variety and quantity of food consumption have increased owing to developments in the agricultural and food industries. Food safety has a substantial socioeconomic impact, and an increasing number of consumers have become aware of its importance. Therefore, simple and cost-effective analytical methods are required to quantify the safety of preservatives. Herein, we report an electrochemical method using double-shelled carbon-confined Ni/NiO (C@Ni/NiO) hollow microspheres to detect diphenylamine (DPA). The microspheres were synthesized by a self-templating hydrothermal method followed by calcination. The hydrothermal temperature and precursor ratio were optimized systematically to prepare double-shelled C@Ni/NiO hollow microspheres. The excellent electrocatalytic activity and electron transport properties of a C@Ni/NiO-modified glassy carbon electrode (GCE) were exploited in the electrochemical oxidation of DPA. Interestingly, the engineered C@Ni/NiO/GCE has a wide dynamic linear range (0.02-473 μM) and a DPA detection limit of 0.007 μM. In addition, the DPA sensor exhibited good selectivity, reproducibility, repeatability, and stability. The practical feasibility of the DPA sensor was evaluated in fruit samples (sweet tomatoes, apples, and red grapes), with considerable recovery.

Polypyrrole and a polypyrrole/nickel oxide composite – single-walled carbon nanotube enhanced photocatalytic activity under visible light

A novel NiO/PPy/SWCNT composite for removal of organic dyes with an emphasis on the effect of photocatalytic charge carrier transport and photoluminescence properties.

Design and tuning functionality of rod-like titanium dioxide-nickel oxide composites via a combinational methodology

TiO₂-NiO composite nanorods were synthesized by combining hydrothermal growth of TiO₂ nanorods and sputtering deposition of NiO film. Crystalline NiO coverage films with various thicknesses were sputter coated onto TiO₂ nanorods by controlling NiO sputtering duration. The crystallographic analyses demonstrate that crystalline rutile TiO₂-cubic NiO composite nanorods were formed herein. In comparison with pristine TiO₂ and NiO, the coverage of NiO crystals on the TiO₂ nanorods led to an enhanced photodegradation activity of the TiO₂-NiO composites towards Rhodamine B dyes under irradiation. Moreover, the TiO₂-NiO composite nanorods with the adequate content of NiO coverage layer show superior gas-sensing responses to 25-200 ppm ammonia gas in comparison with those of the constituent counterparts. The experimental results herein demonstrate that decoration of NiO film on the surfaces of TiO₂ nanorods with tunable coverage sizes via sputtering deposition is a promising approach to design TiO₂-NiO composite nanorods with desirable functionalities.