Search Results (1,695)

Graphitic carbon nitride is recognized as a very promising support structure to anchor single atoms and small, sub-nanometric metal clusters, with vast applications in catalysis. In the current manuscript, we aim to study the geometry and electronic structures of the small, sub-nanometric monometallic (copper or nickel) and bimetallic (copper–nickel) clusters anchored to the graphitic carbon nitride. Our Density Functional Theory (DFT) study reveals that Cu and Ni, when in the form of isolated single atoms, lie in the plane of the support. Once the atoms agglomerate and form small clusters, they tend to bind above the carbon nitride (C₃N₄) plane. The nickel atoms form shorter bonds with the support than the copper atoms do, which is reflected by the binding energies. Atoms directly bound to the support become oxidized, forming electrophilic sites at the surface. The computed negative metal–support binding energies mean that the investigated Cu/Ni-C₃N₄ composites are stable, and the metal species will not easily leach from the support. Full article

Gallic acid (GA), a polyphenol extensively used in the food, wine, and pharmaceutical industries, is known for its inhibitory effects on soil microbial activity. Photocatalytic degradation offers an environmentally friendly solution for GA removal from water. In this work, graphitic carbon nitride (g-C₃N₄) photocatalysts were synthesized by two methods: thermal exfoliation (CN-E) and supramolecular assembly via hydrothermal processing (HCN-II). Structural analyses by XRD, FTIR, and XPS confirmed the formation of the g-C₃N₄ framework, while SEM revealed that CN-E consisted of folded and curled nanosheets, whereas HCN-II displayed a polyhedral–nanosheet hybrid architecture with internal channels. Both materials achieved approximately 80% GA degradation within 180 min under visible-light irradiation, yet HCN-II exhibited a superior apparent rate constant (k = 0.01156 min⁻¹) compared with CN-E. Radical trapping experiments demonstrated that O₂•⁻ and h⁺ were the primary reactive oxygen species involved, with OH• making a minor contribution. The enhanced performance of HCN-II is attributed to its higher surface area, improved light harvesting, and efficient charge separation derived from supramolecular assembly. These findings highlight the potential of engineered g-C₃N₄ nanostructures as efficient, metal-free photocatalysts for the degradation of recalcitrant organic pollutants in water treatment applications. Full article

The metal-free polymeric semiconductor graphitic carbon nitride (g-C₃N₄) has emerged as a promising material for photocatalytic applications due to its responsiveness to visible light, adjustable electronic structure, and stability. This review systematically summarizes recent advances in preparation strategies, including thermal polycondensation, solvothermal synthesis, and template methods. Additionally, it discusses modification approaches such as heterojunction construction, elemental doping, defect engineering, morphology control, and cocatalyst loading. Furthermore, it explores the diverse applications of g-C₃N₄-based materials in photocatalysis, including hydrogen (H₂) evolution, carbon dioxide (CO₂) reduction, pollutant degradation, and the emerging field of piezoelectric photocatalysis. Particular attention is given to g-C₃N₄ composites that are rationally designed to enhance charge separation and light utilization. Additionally, the synergistic mechanism of photo–piezocatalysis is examined, wherein a mechanically induced piezoelectric field facilitates carrier separation and surface reactions. Despite significant advancements, challenges persist, including limited visible-light absorption, scalability issues, and uncertainties in the multi-field coupling mechanisms. The aim of this review is to provide guidelines for future research that may lead to the development of high-performance and energy-efficient catalytic systems in the context of environmental and energy applications. Full article

Phenol is a refractory organic pollutant that is difficult to degrade in wastewater treatment, and efficiently and stably degrading phenol presents a significant challenge. In this study, iron-doped humic acid-based nitrogen–carbon materials were prepared to activate peroxymonosulfate (PMS) for the degradation of phenol. The Fe-N-C/PMS system achieved a phenol degradation rate of 99.71%, which follows a first-order kinetic model, with the reaction rate constant of 0.1419 min⁻¹. The phenol degradation rate remained above 92% in inorganic anions (Cl⁻, SO₄²⁻, HCO₃⁻) and humic acid and the system maintained a 100% phenol removal rate over a wide pH range (3–9). The iron in the catalyst predominantly exists in the forms of Fe⁰ and Fe₃C, and Fe⁰, Fe²⁺/Fe³⁺ are the main active sites that promote PMS activation during the reaction. Additionally, Fe-N-C has a large specific surface area (1041.36 m²/g). Quenching experiments and electron spin resonance (ESR) spectroscopy detected the active free radicals in the Fe-N-C/PMS system: SO₄^•−, •OH, O₂^•−, and ¹O₂. The mechanism for phenol degradation was discussed, involving radical pathways (SO₄^•−, •OH, O₂^•−) and the non-radical pathway (¹O₂), in the Fe-N-C/PMS system activated by Fe⁰, Fe²⁺/Fe³⁺, sp² hybridized carbon, C-O/C-N, C=O, and graphitic nitrogen active sites. This study provides new insights into the synthesis of efficient carbon-based catalysts for phenol degradation and water remediation. Full article

Biomass resources are excellent candidates for carbon electrode materials due to their abundance, renewability, and biodegradability. Herein, the solanaceous crop Tobacco Straw, a rich agricultural by-product, was utilized to prepare biomass-derived carbon material (TsC) and applied as an anode in lithium-ion batteries (LIBs). Doping or composite formation is considered to enhance the electrochemical performance. Doping extra nitrogen (N) atoms into the TsC (denoted as TsNC) demonstrated exceptional reversible specific capacity (475.9 mA h g⁻¹ at the current density of 60 mA g⁻¹ after 500 cycles) and remarkable long-term cycling stability (142.9 mA h g⁻¹ even at a high current density of 1.5 A g⁻¹ after 1000 cycles, much larger than that of TsC), attributed to the increased lithium-ion (Li-ion) adsorption sites including graphitic-N, pyrrolic-N, and pyridinic-N. Furthermore, kinetic analysis revealed that a prominent predominant surface capacitive-controlled behavior was responsible for the superior rate performance of TsNC, which could facilitate rapid charging and discharging at high rates. This work offers valuable insights into the application and modification of nitrogen-doped biomass-derived carbons with outstanding electrochemical properties for LIBs. The strategy also sheds light on enabling waste recycling and generating economic benefits. Full article

The upcycling of spent lithium-ion battery graphite constitutes an essential pathway for mitigating manufacturing expenditures and alleviating ecological burdens. This study proposes an integrated strategy to upcycle spent graphite into high-performance porous expanded graphite (PEG) anodes, leveraging flash Joule heating (FJH) as a core technique for efficient decontamination, interlayer expansion, and active etching. Results show that the binders and impurities are efficiently removed by FJH treatment, and the graphite interlayer spacing is expanded. The iron oxide, which acts as an etching reagent, can then be easily intercalated and laid into the decontaminated graphite for subsequent etching. A subsequent FJH treatment simultaneously releases oxidized intercalants and triggers in-situ metal oxide etching, yielding PEG with a rich porous architecture and enhanced specific surface area. This method successfully prepared high-performance porous expanded graphite anode material with a mesoporous structure. The resulting anode delivers a remarkable capacity retention of 419 mAh·g⁻¹ after 600 cycles at 2C, outperforming the performance of commercial graphite anodes. This innovative approach offers a promising route for sustainable graphite reclamation. Full article

Carbon dots (CDs) derived from renewable biomass are emerging as sustainable alternatives to traditional nanomaterials for applications in bioimaging, sensing, and photonics. In this study, we reported a one-step synthesis of photoluminescent CDs from Laurus nobilis leaves particularly spread in the Mediterranean area. The resulting nanoparticles (NPs) exhibited average diameters of 3–5 nm and high colloidal stability in water. Structural analysis by X-Rays Diffraction revealed the presence of amorphous graphitic domains, while infrared spectroscopy confirmed oxygenated functional groups on the CD surface. Spectrofluorimetric analysis showed excitation-dependent blue–green emission with a maximum at 490 nm that can be applied also as label agents for cells. The environmental sustainability of the synthetic procedure was evaluated through a Life Cycle Assessment (LCA), highlighting that the current impacts were primarily associated with electricity consumption, due to the laboratory-scale nature of the process. These impacts are expected to decrease significantly with future scale-up and process optimization. Full article

The growing demand for sustainable and multifunctional construction materials, particularly those capable of addressing durability and energy challenges, has motivated the development of conductive and photothermally active geopolymers. This study investigated the use of an Fe-rich spinel aggregate (FSA) as a high-density filler in geopolymers composed of ground granulated blast furnace slag and bauxite residue, with a fixed addition of 1 wt% graphite (binder-based) to enhance electrical conductivity. The effects of different FSA replacement percentages (0–100%) on compressive strength, electrical conductivity, photothermal efficiency, and chemical resistance were evaluated. An increase in the FSA content translated to an increase in the final compressive strength, with 100% FSA replacement achieving the highest value of 45.5 ± 2.5 MPa at 28 days. As the FSA content increased, the electrical resistivity decreased to as low as 42 Ω·m at 100% replacement. Under simulated solar flux conditions (1 kW/m²), photothermal analysis revealed that the 100% FSA mixtures exhibited the highest surface temperature increase of 9.8 °C after 300 s, indicating their superior thermal responsiveness. Furthermore, acid immersion in 10% HCl for 28 days showed mass gain in all geopolymers, with the highest gain observed at 50% FSA (+11.51%). Similarly, the strength increased after acid exposure up to a 75% FSA content. These findings highlight the multifunctional potential of FSA-enhanced geopolymers for high-mechanical-performance, electrically conductive, photothermally active, and chemically durable materials as multifunctional construction materials. Full article

The challenges of climate change require in-depth attention and targeted strategies for specific sectors, such as energy and mining. Within the mining sector, climate change imposes constraints on the sustainable extraction of minerals, thereby heightening the importance of several minerals in addressing these challenges. Chile emerges as a pivotal nation due to its substantial reserves of copper, lithium, cobalt, nickel, and graphite, which are essential for energy transition and decarbonization processes. Consequently, Chile must foster gradual processes to establish competitive advantages based on technological and innovative capabilities, thus projecting a competitive and sustainable mining industry. This endeavor should be accompanied by enhancements in policies and instruments to guide development, expanding local value creation. This study examines the global challenges faced by the mining sector in the context of the energy transition and evaluates Chile’s response through an assessment of public policies for mining development. It provides an analysis of the scope of various public policy instruments to establish the link between international agreements and development opportunities, subsequently proposing a series of indicators to assess policy progress. To this end, the Environmental Observatory of Mining Projects is developing indicators to evaluate compliance with these policies. In addressing the nation’s challenges related to green and sustainable mining, 20 indicators have been developed in collaboration with civil society and public and private stakeholders through a design thinking process. These indicators enable the evaluation of aspects such as air quality, water quality, and the surface area affected by tailings, among others. The initial section of the document outlines the global challenges in achieving the carbon neutrality goals set by the IPCC. The subsequent section elaborates on the theoretical framework of the research, addressing theories of economic development and sustainability, public policy approaches considered in recent years, as well as the governance of mining development, with an emphasis on its capacity to articulate industrial policies, promote environmental sustainability, and foster technological innovation. The third section details the research methodology and framework of the study. This study examines how Chile’s mining policies align with the global energy transition. Amid growing demand for critical minerals, climate change, and decarbonization, Chile faces both opportunities and socio-environmental risks. Addressing these challenges requires integrated sustainability strategies and an active state role to ensure inclusive, environmentally responsible, and innovation-driven mining development. Full article

Graphitic carbon nitride (g-C₃N₄)-based materials hold significant promise for environmental remediation, particularly water purification, owing to their unique electronic structure, metal-free composition, and robust chemical stability. However, powdered g-C₃N₄ faces challenges such as particle aggregation, poor recyclability, and limited exposure of active sites. Structuring g-C₃N₄ into hydrogels or aerogels—three-dimensional porous networks offering high surface area, rapid mass transport, and tunable porosity—represents a transformative solution. This review comprehensively examines recent advances in g-C₃N₄-based gels, covering synthesis strategies such as crosslinking (physical/chemical), in situ polymerization, and the sol–gel and template method. Modification approaches including chemical composition and structural engineering are systematically categorized to elucidate their roles in optimizing catalytic activity, stability, and multifunctionality. Special emphasis is placed on environmental applications, including the removal of emerging contaminants and heavy metal ions, as well as solar-driven interfacial evaporation for desalination. Throughout, the critical interplay between gel structure/composition and performance is evaluated to establish design principles for next-generation materials. Finally, this review identifies current challenges regarding scalable synthesis, long-term stability, in-depth mechanistic understanding, and performance in complex real wastewater matrices. This work aims to provide valuable insights and guidance for advancing g-C₃N₄-based hydrogel and aerogel technologies in environmental applications. Full article

In view of the growing demand for flexible, conductive and functional materials for textile gas sensor applications, the effects of ozonation on the properties of expanded graphite (EG) in textile structures were analyzed. Four types of fabrics (cotton, polyamide, viscose, para-aramid) coated with pastes containing EG, which had previously been subjected to a 15-min and 30-min ozonation process, were examined. The paste was prepared using Ebecryl 2002 and the photoinitiator Esacure DP250 and then applied by screen printing. Surface resistance, scanning microscopy and wetting angle analyses were performed. The results showed that short-term ozonation (15 min) notably improved the electrical conductivity and adhesion of EG to the textile substrate, while longer exposure (30 min) led to deterioration of the conductive properties due to excessive functionalization and fragmentation of the conductive layer. The lowest surface resistance was observed in the sample subjected to 15 min of ozonation. The conclusions indicate that a properly controlled ozonation process can increase the usability of EG in sensor applications, especially in the context of smart clothing; however, the optimization of the modification time is crucial for maintaining the integrity and durability of the conductive layer. Full article

In-flight icing presents a critical safety hazard for unmanned aerial vehicles (UAVs), resulting in ice accumulation on propeller surfaces that compromise UAV aerodynamic performance and operational integrity. While hybrid anti-/de-icing systems (i.e., combining active heating with passive superhydrophobic coatings) have been developed recently to efficiently address this challenge, conventional active heating sub-systems utilized in the hybrid anti-/de-icing systems face significant limitations when applied to curved geometries of UAV propeller blades. This necessitates the development of innovative self-heating superhydrophobic coatings that can conform perfectly to complex surface topographies. Carbon-based electrothermal coatings, particularly those incorporating graphite and carbon nanotubes, represent a promising approach for ice mitigation applications. This study presents a comprehensive experimental investigation into the development and optimization of a novel self-heating carbon nanotube (CNT)-based superhydrophobic coating specifically designed for UAV icing mitigation. The coating’s anti-/de-icing efficacy was evaluated through a comprehensive experimental campaign conducted on a rotating UAV propeller under typical glaze icing conditions within an advanced icing research tunnel facility. The durability of the coating was also examined in a rain erosion test rig under the continuous high-speed impingement of water droplets. Experimental results demonstrate the successful application of the proposed sprayable self-heating superhydrophobic coating in UAV icing mitigation, providing valuable insights into the viability of CNT-based electrothermal coatings for practical UAV icing protection. This work contributes to the advancement of icing protection technologies for un-manned aerial systems operating in adverse weather conditions. Full article

In this study, a diamond/diamond-like carbon (DLC) composite coating was designed and fabricated utilizing a combination of chemical vapor deposition (CVD) and magnetron-sputtering-assisted ion beam deposition. This was designed to cope with severe problems such as high wear due to insufficient lubrication under dry sliding conditions with a single diamond. The tribological properties of the fabricated coatings under dry conditions were comparatively evaluated. The results demonstrate that the diamond/DLC composite coatings significantly enhance the tribological performance relative to their single-layer diamond counterparts. Specifically, a 33.73% reduction in the average friction coefficient and a 39.55% decrease in the average wear rate were observed with the MCD (microcrystalline diamond/DLC coating. Similarly, a 16.85% reduction in the average friction coefficient and a 9.69% decrease in the average wear rate were observed with the UNCD (ultrananocrystalline diamond)/DLC coating. Analysis of the worn track morphology and structure elucidated the underlying friction mechanism. It is proposed that the DLC top layer reduces the surface roughness of the underlying diamond coating and mitigates abrasive wear in the dry environment. Furthermore, the presence of the DLC film promotes graphitization via phase transition during sliding, which enhances lubricity and facilitates the establishment of a smooth friction interface. Full article

The existence of dissolved organic matter (DOM) in aquatic environments presents significant challenges to both the environment and public health. This study examines the adsorption efficacy of six organic adsorbents, such as three commercial (coconut shells [CS], palm kernel shells [PKS], and graphite [GR]) and three waste-based materials (plantain peels [PP], water hyacinth leaves [WHL], and corn cobs [CC]) for DOM removal. The waste-derived adsorbents were prepared using thermal and chemical activation techniques, while the commercial adsorbents were used in their standard forms. Adsorption experiments were conducted and analyzed using both kinetic and isotherm models to evaluate removal efficiency and underlying mechanisms. Kinetic modeling revealed that CS, PP, CC, and GR followed pseudo-second-order kinetics, PKS conformed to pseudo-first-order kinetics, and WHL exhibited intra-particle diffusion dominance. The Freundlich isotherm model effectively characterizes the adsorption equilibrium for every material, indicating the multilayer adsorption and heterogeneity of the adsorbent surfaces. Among all tested materials, GR showed the highest DOM removal efficiency (up to 96%) and excellent thermal stability, making it the most effective adsorbent overall. WHL also showed competitive performance, while CS emerged as the most economically viable option despite having slightly lower removal efficiency. Surface area alone does not guarantee adsorption efficiency. Pore accessibility (governed by size/distribution) and surface chemistry (functional group diversity) are equally critical. The findings suggest that both commercial and waste-derived adsorbents hold promise for sustainable and cost-effective water treatment applications. Integrating such materials could enhance the circular economy and offer scalable solutions for addressing water quality issues in developing regions. Full article

A friction composite material which contains cellulose fiber, carbon fiber, wollastonite, graphite, and resin for use in oil-cooled friction units, hydromechanical boxes, and couplings was developed. The fabrication technique includes the formation of a paper layer based on the mixture of stated fibers via a wet-laid process, impregnation of the layer with phenolic resin, and hot pressing onto a steel carrier. The infrared spectra of the polymeric base (phenolic resin) were studied by solvent extraction. The structural-phase analysis of the obtained material was carried out by the SEM method, and the particle size distribution parameters of the composite components were estimated based on the images of the sample surface. The surface roughness parameters of the samples are as follows: Ra = 5.7 μm Rz = 31.4 μm. The tribotechnical characteristics of the material were tested in an oil medium at a load of 5.0 MPa and a rotation mode of 2000 rpm for 180 min in a pair with a steel 45 counterbody. The coefficient of friction of the developed material was 0.11–0.12; the degree of wear was 6.17 × 10⁻⁶ μm/mm. The degree of compression deformation of the composite is 0.36%, and the compressive strength is 7.8 MPa. The calculated kinetic energy absorbed and power level are 205 J/cm² and 110 W/cm², respectively. The main tribotechnical characteristics of the developed friction material correspond to industrial analogues. Full article