Search Results (394)

In this study, wastewater generated from tilapia biofloc aquaculture was treated using the electro-oxidation (EO) process in a batch reactor. Optimal reaction conditions were determined through a robust screening design based on a Taguchi L₉ (3⁴) orthogonal array. The evaluated parameters included three anode–cathode configurations—boron-doped diamond with titanium (BDD–Ti), BDD with copper (BDD–Cu), and BDD with BDD—as well as current intensity (1–2 A), initial pH (5.5–11.5), and treatment time (2.5–3.5 h). The EO process exhibited high removal efficiencies for key water quality indicators. Under optimal conditions (BDD–Ti, i = 2 A, t = 3.5 h, pH₀ = 11.5), removal efficiencies of 96.57% for chemical oxygen demand (COD), 99.06% for total ammoniacal nitrogen (TAN), 67.68% for turbidity, and 81.09% for total organic carbon (TOC) were obtained. Phytotoxicity and bioassay tests further confirmed the detoxification potential of the treated effluent. Overall, the proposed green treatment approach demonstrates that EO is a viable and sustainable strategy for improving effluent quality and advancing water management in intensive aquaculture systems. Full article

The growing demand for sustainable and efficient synthetic methodologies has brought nanocatalysis to the forefront of modern organic chemistry, particularly in the construction of heterocyclic compounds through multicomponent reactions (MCRs). Among various nanocatalysts, calcium oxide nanoparticles (CaO NPs) have gained significant attention because of their strong basicity, thermal stability, low toxicity, and cost-effectiveness. This review provides a comprehensive account of the recent strategies using CaO NPs as heterogeneous catalysts for the green synthesis of nitrogen- and oxygen-containing heterocycles through MCRs. Key reactions such as Biginelli, Hantzsch, and pyran annulations are discussed in detail, with emphasis on atom economy, reaction conditions, product yields, and catalyst reusability. In many instances, CaO NPs have enabled solvent-free or aqueous protocols with high efficiency and reduced reaction times, often under mild conditions. Mechanistic aspects are analyzed to highlight the catalytic role of surface basic sites in facilitating condensation and cyclization steps. The performance of CaO NPs is also compared with other oxide nanocatalysts, showcasing their benefits from green metrics evaluation like E-factor and turnover frequency. Despite significant progress, challenges remain in areas such as asymmetric catalysis, industrial scalability, and catalytic stability under continuous use. To address these gaps, future directions involving doped CaO nanomaterials, hybrid composites, and mechanochemical approaches are proposed. This review aims to provide a focused and critical perspective on CaO NP-catalyzed MCRs, offering insights that may guide further innovations in sustainable heterocyclic synthesis. Full article

Phenolic compounds constitute the predominant group of recalcitrant organic contaminants in coal chemical wastewater. In this study, humic acid and urea were used as carbon and nitrogen sources to prepare nitrogen-doped carbon material (labeled as NC-800) through a two-step calcination process. Using this catalyst (NC-800) to activate PMS for phenol degradation achieved 100% phenol removal across a wide pH range (1–9). The removal rate remained at 99.62% even with high concentrations of inorganic anions or natural organic matter, breaking through the limitations of traditional Fenton-like reactions in terms of acid–base environment and anion influence. The quenching experiment and electron spin resonance (ESR) spectroscopy results indicated that the N-C/PMS system generated three active species hydroxyl radicals (•OH), superoxide radicals (O₂^•−), and singlet oxygen (¹O₂) through the active sites in electron-rich regions such as graphite nitrogen, pyrrole nitrogen, and C=O. An electrochemical test revealed that the system formed a metastable NC-800-PMS* complex during the reaction, indicating the existence of a non-radical pathway of electron transfer. The combination of free radicals (•OH, O₂^•−) and non-free radicals (¹O₂, electron transfer) facilitated the rapid degradation of phenol, providing a theoretical basis for phenol degradation. Full article

Advanced oxidation processes (AOPs) utilizing peroxymonosulfate (PMS) have recently gained attention for effectively removing organic dyes. Biochar, a carbon-based material, can act as a catalyst carrier for PMS activation. This study developed a nitrogen-doped biochar catalyst (NCMR800–2) from waste Chinese medicine residue (CMR) through one-step pyrolysis to efficiently remove Rhodamine B (RhB) from wastewater. Results indicate that NCMR800–2 rapidly achieved complete removal of 20 mg/L Rhodamine B (RhB), the primary focus of this study, within 30 min, while maintaining high degradation efficiencies for other pollutants and significantly outperforming the unmodified material. The material demonstrates strong resistance to ionic interference and operates effectively across a wide pH range. Quenching experiments and in situ testing identified singlet oxygen (¹O₂) as the primary active species in RhB degradation. Electrochemical analysis showed that nitrogen doping significantly enhanced the electrical conductivity and electron transfer efficiency of the catalyst, facilitating PMS decomposition and RhB degradation. Liquid chromatography–mass spectrometry (LC-MS) identified intermediate products in the RhB degradation process. Seed germination experiments and TEST toxicity software confirmed a significant reduction in the toxicity of degradation products. In conclusion, this study presents a cost-effective, efficient catalyst with promising applications for removing persistent organic dyes. Full article

Lithium-oxygen batteries (LOBs) are limited by sluggish oxygen redox kinetics and cathode instability. Herein, we report a cobalt particle catalyst encapsulated in nitrogen-doped carbon (Co@NC) with a three-dimensional hierarchical architecture, synthesized via a chitosan-derived hierarchical porous carbon framework. This innovative design integrates uniformly dispersed ultra-thin carbon shells (11.7 nm), pyridinic nitrogen doping, and Co particles (1.41 μm) stabilized through carbon-support electronic coupling. The hierarchical porosity facilitates rapid O₂/Li⁺ mass transport, while pyridinic N sites act as dual-function electrocatalytic centers for Li₂O₂ nucleation and charge transfer kinetics. Co@NC achieves 11,213 mAh g⁻¹ at 200 mA g⁻¹ (126.5% higher than nitrogen-doped carbon) and maintains 1.54 V overpotential (500 mAh g⁻¹). These metrics outperform benchmark catalysts, addressing kinetic and stability challenges in LOBs. The study advances electrocatalyst design by integrating structural optimization, heteroatom doping, and electronic coupling strategies for high-performance metal–air batteries. Full article

The widespread contamination of aquatic systems by ciprofloxacin (CIP)—a persistent fluoroquinolone antibiotic—poses severe ecological risks due to its antibacterial resistance induction. Conventional sulfate radical-based advanced oxidation processes (SR-AOPs) suffer from inefficient catalyst synthesis, exemplified by low-yield ZIF-67 precursors (typically <25%). To address this, a nitrogen-doped carbon composite Co₃O₄/N@C was synthesized via ammonia-assisted ligand exchange followed by pyrolysis, using N-doped ZIF-67 as a self-sacrificial template. The ammonia incorporation quadrupled precursor yield compared to ammonia-free methods. This catalyst activated peroxydisulfate (PDS) to degrade 95% CIP within 90 min under the optimized conditions (0.5 g/L catalyst, 2 mmol/L PDS, pH 5), representing a 30% enhancement over non-ammonia analogs. Mechanistic studies identified singlet oxygen (¹O₂) as the dominant reactive species, facilitated by N-doped carbon-mediated electron transfer. This strategy overcomes the scalability barrier of MOF-derived catalysts for practical antibiotic wastewater remediation. Full article

The hierarchical porosity and active sites of porous carbon materials have significant impacts on the oxygen reduction reaction (ORR) process. The heteroatom-doped porous carbon materials (Z67-900, Z8-900, Z11-900, Z12-900) were synthesized by pyrolysis of ZIFs to reveal the synergistic effect of hierarchical porosity and Co-N_x sites. The structures of prepared materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, and nitrogen adsorption. The results of electrocatalytic performance show that Z67-900 has the best performance among the four materials prepared. The onset potential (E₀) of Z67-900 is close to commercial Pt/C (20%), and the half-wave potential (E_1/2) of Z67-900 is 80 mV positive than that of Pt/C in an O₂-saturated 0.1 M KOH solution (1600 rpm) with sweep rate of 5 mV·s⁻¹. Moreover, Z67-900 has better methanol resistance. The hierarchical pore structure of Z67-900 facilitates mass transfer, while the Co-N_x sites provide active catalytic centers. This study provides a solid foundation for the rational design of highly efficient ZIF-derived heteroatom-doped catalysts. Full article

Advances in OLED display technology have increased the demand for high-performance luminescent materials, yet efficient red emitters with narrow emission spectra remain rare. Here, two new polycyclic compounds (O-QA and S-QA) are designed by incorporating oxygen/sulfur into a carbonyl/nitrogen skeleton. Photophysical and theoretical studies reveal their hybridized local and charge-transfer state characteristics. In toluene, O-QA and S-QA show photoluminescence peaks at 586/579 nm with narrow emission spectra, while doped films exhibit strong red emissions peaking at 598/600 nm with high PL quantum yields of 67%/60%. The OLEDs using these emitters achieve red electroluminescence (EL) peaks at 598/602 nm, and attain maximum external quantum efficiencies of 7.36%/14.54%. This work may provide guidance for the development of narrow-spectrum red emitters based on carbonyl/nitrogen frameworks. Full article

High-Temperature Proton-Exchange Membrane Fuel Cells (HT-PEMFCs) represent a promising clean energy technology and are valued for their fuel flexibility and simplified balance of plant. Their commercialization, however, is critically hindered by the prohibitive cost and resource scarcity of platinum-group metal (PGM) catalysts. The challenge is amplified in the phosphoric acid (PA) electrolyte of HT-PEMFCs, where the severe anion poisoning of PGM active sites necessitates impractically high catalyst loadings. This review addresses the urgent need for cost-effective alternatives by providing a comprehensive assessment of recent advancements in non-precious metal (NPM) catalysts for the oxygen reduction reaction (ORR) in HT-PEMFCs. It systematically explores synthesis strategies and structure–performance relationships for emerging catalyst classes, including transition metal compounds, metal–nitrogen–carbon (M-N-C) materials, and metal-free heteroatom-doped carbons. A significant focus is placed on M-N-C catalysts, particularly those with atomically dispersed Fe-Nx active sites, which have emerged as the most viable replacements for platinum due to their high intrinsic activity and notable tolerance to phosphate poisoning. This review critically analyzes key challenges that impede practical application, such as the trade-off between catalyst activity and stability, mass transport limitations in thick electrodes, and long-term degradation in the harsh PA environment. Finally, it outlines future research directions, emphasizing the need for a synergistic approach that integrates computational modeling with advanced operando characterization to guide the rational design of durable, high-performance catalysts and electrode architectures, thereby accelerating the path to commercial viability for HT-PEMFC technology. Full article

Amorphous indium gallium zinc oxide (a-IGZO) is widely used as an oxide semiconductor in the electronics industry due to its low leakage current and high field-effect mobility. However, a-IGZO suffers from notable limitations, including crystallization at temperatures above 600 °C and the high cost of indium. To address these issues, nitrogen-doped zinc oxynitride (ZnON), which can be processed at room temperature, has been proposed. Nitrogen in ZnON effectively reduces oxygen vacancies (V_O), resulting in enhanced field-effect mobility and improved stability under positive bias stress (PBS) compared to IGZO. In this study, selective deep ultraviolet femtosecond (DUV fs) laser annealing was applied to the channel region of ZnON thin-film transistors (TFTs), enabling rapid threshold voltage (Vth) modulation within microseconds, without the need for vacuum processing. Based on the electrical characteristics of both Vth-modulated and pristine ZnON TFTs, an NMOS inverter was fabricated, demonstrating reliable performance. These results suggest that laser annealing is a promising technique, applicable to various logic circuits and electronic devices. Full article

Fibrate pharmaceuticals (fibrates), as a widespread class of emerging contaminants, pose potential risks to both ecological systems and human health. The photocatalytic system based on nitrogen (N) and fluorine (F) co-doped TiO₂ nanotube arrays (NF-TNAs) provides a renewable solution for fibrate pharmaceutical removal from water, powered by inexhaustible sunlight. In this study, the degradation of two typical fibrates, i.e., bezafibrate (BZF) and ciprofibrate (CPF), under simulated sunlight irradiation through NF-TNAs were investigated. The photocatalytic degradation of BZF/CPF was achieved through combined radical and non-radical oxidation processes, while the generation and reaction mechanisms of associated reactive oxygen species (ROS) were examined. Electron paramagnetic resonance detection and quenching tests confirmed the existence of h⁺, •OH, O₂^•−, and ¹O₂, with O₂^•− playing the predominant role. The transformation products (TPs) of BZF/CPF were identified through high-resolution mass spectrometry analysis combined with quantum chemical calculations to elucidate the degradation pathways. The influence of co-existing ions and typical natural organic matters (NOM) on BZF/CPF degradation were also tested. Eventually, the ecological risk of BZF/CPF transformation products was assessed through quantitative structure–activity relationship (QSAR) modeling, and the results showed that the proposed photocatalytic system can largely alleviate fibrate toxicity. Full article

100 nm thick TiO₂/TiN bilayers with varying thickness ratios were deposited via reactive sputtering of a Ti target in controlled oxygen and nitrogen atmospheres. Post-deposition annealing in air at 600 °C was performed to induce nitrogen diffusion through the oxygen-deficient TiO₂ layer. The resulting changes in morphology and chemical environment were investigated in detail using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and UV-Vis spectroscopy. Detailed TEM and XPS analyses have confirmed nitrogen diffusion across the TiO₂ layer, with surface nitrogen concentration and the ratio of interstitial to substitutional nitrogen dependent on the TiO₂/TiN mass ratio. Optical studies demonstrated modifications in optical constants and a reduction of the effective bandgap from 3.2 eV to 2.6 eV due to new energy states introduced by nitrogen doping. Changes in surface free energy induced by nitrogen incorporation showed a correlation to nitrogen doping sites on the surface, which had positive effects on overall photocatalytic activity. Photocatalytic activity, assessed through methylene blue degradation, showed enhancement attributed to nitrogen doping. Additionally, deposition of a 5 nm gold layer on the annealed sample enabled investigation of synergistic effects between nitrogen doping and gold incorporation, resulting in further improved photocatalytic performance. These findings establish the TiO₂/TiN bilayer as a versatile platform for supporting thin gold films with enhanced photocatalytic properties. Full article

The efficient depolymerization of lignin has become a key challenge in the preparation of high-value-added chemicals. Graphitic carbon nitride (g-C₃N₄)-based photocatalytic system shows potential due to its mild and green characteristics over other depolymerization methods. However, its inherent defects, such as a wide band gap and rapid carrier recombination, severely limit its catalytic performance. In this paper, a g-C₃N₄ modification strategy of K⁺ doping and surface alkalinization is proposed, which is firstly applied to the photocatalytic depolymerization of the lignin β-O-4 model compound (2-phenoxy-1-phenylethanol). K⁺ doping is achieved by introducing KCl in the precursor thermal polymerization stage to weaken the edge structure strength of g-C₃N₄, and post-treatment with KOH solution is combined to optimize the surface basic groups. The structural/compositional evolution of the materials was analyzed by XRD, FTIR, and XPS. The morphology/element distribution was visualized by SEM-EDS, and the optoelectronic properties were evaluated by UV–vis DRS, PL, EIS, and transient photocurrent (TPC). K⁺ doping and surface alkalinization synergistically regulate the layered structure of the material, significantly increase the specific surface area, introduce nitrogen vacancies and hydroxyl functional groups, effectively narrow the band gap (optimized to 2.35 eV), and inhibit the recombination of photogenerated carriers by forming electron capture centers. Photocatalytic experiments show that the alkalinized g-C₃N₄ can completely depolymerize 2-phenoxy-1-phenylethanol with tunable product selectivity. By adjusting reaction time and catalyst dosage, the dominant product can be shifted from benzaldehyde (up to 77.28% selectivity) to benzoic acid, demonstrating precise control over oxidation degree. Mechanistic analysis shows that the surface alkaline sites synergistically optimize the C_β-O bond breakage path by enhancing substrate adsorption and promoting the generation of active oxygen species (·OH, ·O₂⁻). This study provides a new idea for the efficient photocatalytic depolymerization of lignin and lays an experimental foundation for the interface engineering and band regulation strategies of g-C₃N₄-based catalysts. Full article

5-Hydroxymethylfurfural (HMF) is a versatile platform molecule with the potential to replace many fossil fuel derivatives. It can be obtained through the dehydration of carbohydrates. In this study, we present a simple and cost-effective microwave-assisted method for producing HMF. This method involves the use of readily available sucrose as a substrate and glucose-derived bifunctional hydrochars as carbocatalysts. These catalysts were produced via hydrothermal carbonisation using thiourea and urea as nitrogen and sulphur sources, respectively, to introduce Brønsted acidic and basic sites into the materials. Using a microwave reactor, we found that the S, N-doped hydrochars were active in sucrose dehydration in water. Catalytic results showed that HMF yield depended on the balance between acidic and basic sites as well as the types of S and N species present on the surfaces of these hydrochars. The best-performing catalyst achieved an encouraging HMF yield of 37%. The potential of N, S-co-doped biochar as a green solid catalyst for various biorefinery processes was demonstrated. A simple kinetic model was developed to elucidate the kinetics of the main reaction pathways of this cascade process, showing a very good fit with the experimental results. The calculated rate constants revealed that reactions with a 5% sucrose loading exhibited significantly higher fructose dehydration rates and produced fewer side products than reactions using a more diluted substrate. No isomerisation of glucose into fructose was observed in an air atmosphere. On the contrary, a limited rate of isomerisation of glucose into fructose was recorded in an oxygen atmosphere. Therefore, efforts should focus on achieving a high glucose-to-fructose isomerisation rate (an intermediate reaction step) to improve HMF selectivity by reducing humin formation. Full article

To address mass transport limitations in carbon nanofiber membrane electrodes for overall water splitting, a self-supporting nitrogen-doped hollow carbon nanofiber membrane embedded with Co/Co₂P heterojunctions (Co/Co₂P-NCNFs-H) was fabricated via continuous coaxial electrospinning. The architecture features uniform hollow channels (200–250 nm diameter, 30–50 nm wall thickness) and a high specific surface area (254 m² g⁻¹), as confirmed by SEM, TEM, and BET analysis. The Co/Co₂P heterojunction was uniformly dispersed on nitrogen-doped hollow carbon nanofibers through electrospinning, leverages interfacial electronic synergy to accelerate charge transfer and optimize the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Electrochemical tests demonstrated exceptional catalytic activity, achieving current densities of 100 mA cm⁻² at ultralow overpotentials of 405.6 mV (OER) and 247.9 mV (HER) in 1.0 M KOH—surpassing most reported transition metal catalysts for both half-reactions. Moreover, the electrode exhibited robust long-term stability, maintaining performance for nearly 20 h at 0.6 V (vs. Ag/AgCl) (OER) and over 250 h at −1.5 V (vs. Ag/AgCl) (HER), attributed to the mechanical integrity of the hollow architecture and strong metal–carbon interactions. This work demonstrates that integrating hollow nanostructures (enhanced mass transport) and heterojunction engineering (optimized electronic configurations) creates a scalable strategy for designing efficient bifunctional catalysts, offering significant promise for sustainable hydrogen production via water electrolysis. Full article