Search Results (91)

Carbon dots (CDs) have recently emerged as a novel class of eco-friendly and multifunctional corrosion inhibitors owing to their nanoscale dimensions, tunable surface functionalities, and sustainable synthesis pathways. This review summarizes the latest progress in CD-based inhibitors, focusing on synthesis methods, applications, and inhibition mechanisms. Various strategies—including hydrothermal/solvothermal treatment, microwave irradiation, pyrolysis, electrochemical synthesis, and chemical oxidation—have been employed to obtain CDs with tailored size, heteroatom doping, and surface groups, thereby enhancing their inhibition efficiency. CDs have demonstrated remarkable applicability across diverse corrosive environments, including acidic, neutral chloride, CO₂-saturated, microbiologically influenced, and alkaline systems, often achieving inhibition efficiencies exceeding 90%. Mechanistically, their performance arises from strong adsorption and compact film formation, heteroatom-induced electronic modulation, suppression of anodic and cathodic reactions, and synergistic effects of particle size and structural configuration. Compared with conventional inhibitors, CDs offer higher efficiency, environmental compatibility, and multifunctionality. Despite significant progress, challenges remain regarding precise structural control, scalability of synthesis, and deeper mechanistic understanding. The effectiveness of CDs inhibitors is highly dependent on factors such as pH, temperature, inhibitor concentration, and exposure time, which should be tailored for specific applications to maximize performance. Future research should focus on integrating sustainable synthesis with rational heteroatom engineering and advanced characterization to achieve long-term, cost-effective, and environmentally benign corrosion protection solutions. Compared to earlier reviews, this review discusses the emerging trends in the field of CDs as corrosion inhibitors. Full article

In this study, a novel activated carbon (AC) (AC-Ba(OH)₂) was synthesized through a three-step process (including hydrothermal carbonization (at 250 °C), alkali activation by Ba(OH)₂, and pyrolysis (at 850 °C)), from Plane tree fruits (PTFs). By using various experimental methods for material characterization, it was established that the resulting material possesses a variety of oxygen functional groups, rich in alkaline earth oxides (BaO/CaO), SiO₂, consisting of graphitized carbon with graphene structures. A detailed kinetic and thermodynamic analysis of AC-Ba(OH)₂ thermal restoring was also carried out. Thermodynamic analysis revealed the existence of a true thermodynamic compensation effect (TCE) during restoration. Restoration was controlled by entropy, where experimental temperatures are above the iso-entropic temperature, i.e., the temperature where contributions of enthalpy and entropy to activation free energy are balanced. Kinetic modeling has shown that restoration allows carbon material to be significantly modified by removing oxygen-containing groups via diffusion, changing active sites on the surface, and preparing material for catalyst support. CaO and SiO₂ act as catalysts, while BaO alters graphene surface properties. Isothermal prediction tests have shown an extremely high long-term stability of modified AC-Ba(OH)₂, supporting an elevated activity, selectivity, and lifetime, as well. The restoring process resulted in an energy consumption of 0.762 kWh, which is equivalent to the reactivation of AC with a lower specific surface area. Manufactured AC and its thermally modified counterpart can be used as both a catalyst support and catalyst for reforming processes, such as methanol synthesis, biogas purification, and dry reforming of methane. Full article

Kaolin from the Donigazza deposit (NW Sardinia, Italy) was used to investigate the mechanisms of zeolite crystallization under alkaline hydrothermal conditions. The starting material, composed mainly of kaolinite and opal-CT with minor quartz and low iron content, was reacted with NaOH solutions (1–5 mol L⁻¹) at 100 °C for 12–168 h. XRD analyses revealed the formation of zeolitic and related phases, including NaP1, NaP2, analcime, sodalite, and cancrinite, with zeolite contents reaching up to 100%. The extent of kaolinite dissolution varied with both NaOH concentration and reaction time, with complete transformation occurring at ≥3 mol L⁻¹ and ≥48 h. SEM imaging showed idiomorphic crystals (100 nm–10 μm) and globular nanoparticles (<50 nm), likely Na-Al-Si gels. Phase distribution reflected evolving solution chemistry, particularly changes in the Si/Al ratio due to differential dissolution of opal-CT and kaolinite. Crystallization proceeded via both classical (monomer addition) and non-classical (particle attachment) pathways, influenced by supersaturation, gel composition, and reaction kinetics. The transition from NaP1 to NaP2, and the development of metastable phases, indicate kinetic control consistent with Ostwald’s step rule. These results provide insights into the complex dynamics of zeolite formation from natural aluminosilicate precursors in alkaline environments. Full article

The Yanlinsi gold deposit, located in the middle section of the Jiangnan Orogenic Belt, is one of the typical gold deposits in northeastern Hunan Province. Diabase dikes are exposed by underground workings and drill holes in the mining area. The dikes strike NW and cut the NE-trending gold ore body. To investigate the petrogenetic age, characteristics of the magmatic source area, and tectonic setting of the diabase dikes in the Yanlinsi gold mining area, northeastern Hunan, and to determine the mineralization age of the deposit, in this paper, diabase dike LA-ICP-MS zircon U-Pb dating, whole-rock geochemistry, and gold-bearing quartz vein LA-ICP-MS zircon U-Pb dating were studied. The results of LA-ICP-MS zircon U-Pb dating indicate that the diabase was emplaced at an age of 219.5 Ma, belonging to the late Indosinian. The investigated diabase dikes are characterized by low SiO₂ (43.68%–46.55%), high MgO (7.78%–9.84%), and high Mg# (65.0–68.7) values, belonging to the alkaline basalt series with high potassium. The chondrite-normalized REEs patterns show highly fractionated LREEs and HREEs ((La/Yb)_N = 11.21–14.82), and the primitive mantle-normalized spider patterns show enrichment in large ion lithophile elements (e.g., Rb, Ba, K and Sr) and relative depletion in high field strength elements (e.g., Nb, Ta, and P), similar to those of ocean island-like basalt (OIB). Rock geochemical characteristics indicate that the magma of the Yanlinsi diabase was formed by partial melting of the enriched mantle (EM II), with the source region being spinel-garnet lherzolite. The degree of partial melting was approximately 10%–15%, and the assimilation and contamination with continental crustal materials were weak. Meanwhile, weak fractional crystallization of olivine, clinopyroxene, and apatite occurred during the magma evolution process. On the basis of a synthesis of previous research results, it is concluded that the Yanlinsi diabase formed in an extensional tectonic setting after intracontinental collisional orogeny. The LA-ICP-MS U-Pb age of hydrothermal zircons from quartz veins in the main mineralization stage of the Yanlinsi gold deposit is 421.9 ± 1.5 Ma. Combined with the cross-cutting relationships between mafic dikes and gold veins (ore bodies), it is determined that the main mineralization stage of the deposit formed during the Caledonian Period. Full article

Fly ash from coal-fired power plants is a promising precursor for zeolite synthesis due to its aluminosilicate-rich composition. However, its direct utilization is often limited by impurities and a low silicon-to-aluminum ratio (SAR). This study demonstrates the conversion of Class C fly ash from the Soma thermal power plant (Turkey) into FAU- and CHA-type zeolites through optimized acid leaching and hydrothermal synthesis. Acid treatment increased the SAR from 1.33 to 2.85 and effectively reduced calcium-, sulfur-, and iron-bearing impurities. The SAR enhancement by acid leaching was found to be reproducible among Class C fly ashes, whereas Class F materials exhibited a limited response due to their acid-resistant framework. Subsequent optimization of alkaline fusion-assisted synthesis enabled selective crystallization of FAU and CHA, while GIS and MER appeared under prolonged crystallization or higher alkalinity. SEM revealed distinct morphologies, with MER forming rod-shaped clusters, and CHA exhibiting disc-like aggregates. Water sorption analysis showed superior uptake for metastable FAU (~23 wt%) and CHA (~18 wt%) compared to stable GIS and MER (~12–13 wt%). Overall, this study establishes a scalable and sustainable route for producing high-performance zeolites from industrial fly ash waste, offering significant potential for adsorption-based applications in dehumidification, heat pumps, and gas separation. Full article

The valorization of volcanic ash as a raw material for advanced functional materials offers dual benefits for both the environment and technology. Firstly, it diverts waste from landfills, thereby reducing the environmental footprint of volcanic deposits. Secondly, it contributes to the circular economy by transforming an abundant natural residue into a high-value product. In this study, zeolites were synthesized from the ash of the Ubinas volcano via the hydrothermal method in an alkaline medium. A systematic investigation was conducted to ascertain the influence of NaOH concentration and reaction temperature on synthesis efficiency and final material properties. The crystalline phases and morphology of the products were characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), while textural and thermal properties were evaluated through the Brunauer–Emmett–Teller (BET) method and Thermogravimetric Analysis (TGA). The results revealed that both temperature and NaOH concentration significantly affected the physicochemical properties of the zeolites. Four zeolite types were obtained; among them, Zeolite Z4 (synthesized with 3 M NaOH at 150 °C) exhibited the highest adsorption capacity, with a specific surface area of 35.60 m²/g, while Zeolite Z1 (synthesized at 120 °C with 1.5 M NaOH and 27.85 m²/g) displayed superior thermal stability and crystallinity. These variations in thermal and textural properties were reflected in the catalytic pyrolysis performance of polypropylene (PP). Zeolite Z3 (synthesized at 150 °C with 1.5 M NaOH) achieved the highest gaseous product yield (80.2%), despite lacking the expected zeolitic crystalline phases. In contrast, Zeolite Z2 (synthesized at 120 °C with 3 M NaOH) yielded 57.7% gaseous products and stood out for its predominant analcime phase, characteristic of zeolitic materials. In summary, this study demonstrates that volcanic ash-derived zeolites not only enhance synthesis efficiency and functional performance but also represent a sustainable strategy for waste valorization, closing material loops and enabling the recovery of high-calorific gaseous products from plastic waste. Full article

The gas-phase synthesis of anisole from methanol and phenol is currently recognized as the process with the most theoretical research value and industrial application prospect. LaPO₄ has attracted widespread attention due to its excellent catalytic activity, robust water resistance, and high-temperature performance. In this work, rod-like monoclinic, mixed phase, and hexagonal LaPO₄ were synthesized using the hydrothermal method, and their catalytic activity was evaluated. The results showed that the catalytic activity of the hexagonal phase is higher than that of the monoclinic phase. By combining relevant characterization methods and DFT theoretical calculations, it is clarified that the higher acidity and stronger alkalinity of the exposed surface of hexagonal LaPO₄ are the main reasons for its higher activity. Further research has revealed that the main cause of LaPO₄ deactivation is carbon deposition on the catalyst surface. Full article

The sustainable development of our society faces significant challenges, including the need for environmentally friendly energy storage devices. Our work is concerned with the conversion of Mo-based recycled industrial waste into active nanocatalysts for energy storage applications. To reach this goal, we employed hydrothermal synthesis, a low-cost and temperature-scalable method. The proposed synthesis produces MoO₃ nanobelts (50–200 nm in width and 2–5 µm in length) with a high yield, about 74%. The synthesized nanostructures were characterized in 1 M KOH and 1 M NH₄OH, as alkaline environments are a promising choice for the development of eco-friendly devices. To investigate the material’s behaviour cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements were carried out. From CV curves, it was possible to evaluate the specific capacitance values of 290 and 100 Fg⁻¹ at 5 mVs⁻¹ in 1 M KOH and 1 M NH₄OH, respectively. Also, GCD was employed to evaluate the specific capacitance of the material, resulting in 75 and 60 Fg⁻¹ in 1 M KOH and 1 M NH₄OH, respectively. CV and GCD analyses revealed that MoO₃ nanobelts act as two different types of energy storage devices: supercapacitors and pseudocapacitors. Additionally, EIS allowed us to distinguish between the resistive and capacitive behaviour contributions depending on the electrolyte. Furthermore, it provided a comprehensive electrochemical characterization in different alkaline electrolytes, with the intention of conjugating waste management and sustainable energy storage device production. Full article

Magnetically separable TiO₂-based composite photocatalysts have gained significant interest in the past two decades; however, the optimization of their synthesis and the stabilization of the magnetic iron oxide within the composite is still an open challenge. The present study investigates the photocatalytic behavior and recyclability of TiO₂-Fe₃O₄ composites, with emphasis on a possible correlation between pollutant degradation efficiency, recyclability, iron oxide stability, and the phase composition of the chosen TiO₂ base. Magnetite nanoparticles were synthesized under varied temperature and alkaline conditions to identify optimal parameters for achieving the desirable magnetic properties. The magnetic nanoparticles were integrated into composite systems with either commercial TiO₂ (Evonik Aeroxide P25 with anatase–rutile mixed phase) or a hydrothermally synthesized anatase TiO₂. The P25-based composite removed 99% paracetamol from aqueous solutions under UV-A irradiation and demonstrated successful recyclability, maintaining 96% paracetamol degradation efficiency after four uses. In contrast, the anatase TiO₂-based magnetic composite exhibited a lower performance (70%) and a significantly hindered recyclability (45% after four cycles). The difference in performance was attributed to variations in the phase composition of the employed TiO₂ in the composites and, consequently, in their charge separation mechanisms. Full article

Bioethanol from sugarcane bagasse is a promising second-generation biofuel due to its abundance as a sugar industry by-product. Herein, enzymatic hydrolysate obtained from sugarcane bagasse pretreated with optimized hydrothermal alkaline sulfite (HAS) was evaluated for its fermentability using Saccharomyces cerevisiae PE-2 and Scheffersomyces stipitis CBS 5773. The HAS pretreatment achieved a high delignification rate (63%), resulting in a cellulose- and hemicellulose-enriched substrate (55% and 27%, respectively). While the cellulose content remained relatively constant, hemicellulose content was reduced by 25%, with significant removal of acetyl groups (80%) and arabinan groups (39%). The pretreated bagasse exhibited high digestibility, applying 10 FPU (filter paper unit) cellulase together with 10 CBU (cellobiose unit) β-glucosidase per gram of dry bagasse in the hydrolysis step, yielding 72% glucan and 66% xylan conversion within 72 h. The resulting hydrolysate was efficiently fermented by S. cerevisiae and S. stipitis, achieving ethanol yields of 0.51 and 0.43 g/g of sugars, respectively. The fermentation kinetics were comparable to those observed in a synthetic medium containing pure sugars, demonstrating the effectiveness of HAS pretreatment in generating readily fermentable, carbohydrate-rich substrates. HAS pretreatment enabled improved conversion of sugarcane bagasse into fermentation-ready sugars, constituting a potential resource for bioethanol synthesis applying both S. cerevisiae and S. stipitis in the future. Full article

In this study, a green hydrothermal synthesis method was employed to produce Mn₃O₄ and Mn₃O₄/β-MnO₂ nanostructures using EET-50, an organic extract obtained from a by-product of Carménère wine production. The biomolecules in EET-50 acted as reducing agents due to their electron-donating functional groups, enabling nanostructure formation without the need for additional chemical reductants. Morphological characterization by SEM revealed that a KMnO₄/EET-50 mass ratio of 3:1 led to the synthesis of nano-octahedra alongside rod-like structures, with shorter reaction times favoring the development of isolated nano-octahedra ranging from 100 nm to 170 nm. Structural analyses by XRD and Raman spectroscopy confirmed the formation of mixed-phase Mn₃O₄/β-MnO₂ and Mn₃O₄ (hausmannite). Electrochemical performance tests demonstrated that Mn₃O₄ nano-octahedra exhibited a superior specific capacitance of 236.27 F/g at 1 mA/g, surpassing the mixed-phase sample by 28.3%, and showed excellent capacitance retention (99.98%) after 100 cycles at 8 mA/g. Additionally, the Mn₃O₄ nano-octahedra exhibited enhanced oxygen evolution reaction performance in alkaline media, with an overpotential of 0.430 V vs. RHE and a Tafel slope of 205 mV/dec. These results underscore the potential of Mn₃O₄ nano-octahedra, synthesized via a green route using grape pomace extract as a reducing agent, offering an environmentally friendly alternative for applications in energy storage and electrocatalysis. Full article

Electro-oxidation of urea (UOR) in alkaline medium is one of the most effective alternative ways of producing green hydrogen, as the oxidation potential in UOR is less and thermodynamically more favorable than conventional water oxidation. The development of cost-effective materials in catalyzing UOR is recently seeking more attention in the research hotspot. Suitably modifying the Ni-based catalysts towards active site creation and preventing surface passivation is much important in this context, following which we reported the synthesis of Ni₃S₂ (NS) supported with CuCo (CC) bimetallic (NSCC). A simple hydrothermal route for NS synthesis and the electrodeposition method for CuCo (CC) deposition is adapted in a self-supported manner. The NS and CC catalysts exhibited sheet-like morphology, as confirmed by SEM and TEM analysis. The bimetallic CC deposition prevented the surface passivation of nickel sulfide (NS) over oxygen evolution reaction (OER) and improved the charge-transfer kinetics. The NSCC catalyst catalyzed UOR in an alkaline medium, which required a lower potential of 1.335 V vs. RHE to attain the current density of 10 mAcm⁻², with a lower Tafel slope value of 131 mVdec⁻¹. In addition, a two-electrode cell setup is constructed with an operating cell voltage of 1.512 V for delivering 10 mAcm⁻² current density. This study illustrates the new strategy of designing heterostructure catalysts for electrocatalytic UOR. Full article

Recently, the development of nanoparticle pigments has attracted interest in chemical preparation due to their potential functional properties, such as phosphate-based pigments. The present research focuses on the feasibility of synthesising the BaCr₂(P₂O₇)₂ pigment under hydrothermal conditions. The effect of the microstructural features of ceramic pigments (the crystalline structure, morphology, and particle size) on their optical properties (colour and reflectance) was also studied. The BaCr₂(P₂O₇)₂ compound was prepared in different fluid media, including water and NaOH solutions (0.5–1.0 M), at several reaction temperatures (170–240 °C) and intervals (6–48 h). The single-phase BaCr₂(P₂O₇)₂ did not crystallise without by-products (BaCr₂O₁₀, BaCr₂(PO₇)₂) in water and the alkaline solutions, even at 240 °C for 48 h; in these fluids, the ionic Cr³⁺ species oxidised to Cr⁶⁺. In contrast, the BaCr₂(P₂O₇)₂ single-phase crystallisation was favoured by adding urea as a reductant agent (25.0–300.0 mmol). Monodispersed BaCr₂(P₂O₇)₂ fine particles with a mean size of 44.0 nm were synthesised at a low temperature of 170 °C for 6 h with 0.5 M NaOH solution in the presence of 50.0 mmol urea. The phosphate pigment particle grew to approximately 62.0 nm by increasing the treatment temperature to 240 °C. A secondary dissolution–recrystallisation achieved after 24 h triggered a change in the particle morphology coupled with the incrementation of the concentration of NaOH in the solution. The pyrophosphate BaCr₂(P₂O₇)₂ pigments prepared in this study belong to the green colour spectral space according to the CIELab coordinates measurement, and exhibit 67.5% high near-infrared (NIR) solar reflectance. Full article

Electrocatalytic nitrate reduction to ammonia (ENRA) presents a promising strategy for simultaneous environmental remediation and sustainable ammonia synthesis. In this work, a Cu–Co bimetallic catalyst supported on functionalized reduced graphene oxide (RGO) was systematically designed to achieve efficient and selective ammonia production. Surface oxygen functional groups on graphene oxide (GO) were optimized through alkaline hydrothermal treatments, enhancing the anchoring capacity for metal active sites. Characterization indicated the successful formation of uniform Cu–Co bimetallic heterointerfaces comprising metallic and oxide phases, which significantly improved catalyst stability and performance. Among the studied compositions, Cu₆Co₄/RGO exhibited superior catalytic activity, achieving a remarkable ammonia selectivity of 99.86% and a Faradaic efficiency of 96.54% at −0.6 V (vs. RHE). Long-term electrocatalysis demonstrated excellent durability, with over 90% Faradaic efficiency maintained for ammonia production after 20 h of operation. In situ FTIR analysis revealed that introducing Co effectively promoted water dissociation, facilitating hydrogen generation (*H) and accelerating the transformation of nitrate intermediates. This work offers valuable mechanistic insights and paves the way for the design of highly efficient bimetallic electrocatalysts for nitrate reduction and ammonia electrosynthesis. Full article

Pursuing cost-effective non-precious metal electrocatalysts is a key challenge in the field of sustainable energy conversion. Transition metal dichalcogenides, known for their unique electronic structure, demonstrate superior electrocatalytic capabilities for the hydrogen evolution reaction (HER), yet their effectiveness is still lacking. In the present study, a CuS/Co₃S₄@MWCNT composite was fabricated via single-step hydrothermal synthesis for HER applications. This catalyst exploited the synergistic effects between CuS and Co₃S₄ to increase edge site functionalities and metallic conductivity, thereby resulting in high catalytical activity within the material. Furthermore, the incorporation of multi-walled carbon nanotubes (MWCNTs) into the composite effectively enhanced electron transfer kinetics throughout the HER process. Notably, thiourea serves a dual function in this synthesis, acting both as a reducing agent and as a sulfur source for the formation of metal sulfides. When evaluated in a 1 M KOH alkaline electrolyte, the synthesized nanocomposite exhibited a minimal overpotential of 300 mV to reach a current density of 10 mA/cm², and a Tafel slope of merely 76.2 mV/dec, indicative of its good HER catalytic activity. These findings underscore the composite’s potential for application in hydrogen production technologies. Full article