Search Results (78)

This short review provides a focused overview of recent advances in catalytic systems for water purification, with particular attention to photocatalysis, Fenton-like processes, and biocatalysis. While not intended as a comprehensive survey, this review is grounded primarily in recent work from our research group, supported by comparisons with relevant studies from the broader literature. Emphasis is placed on the role of graphene-based materials, particularly aerogels, hydrogels, and xerogels, as functional platforms for catalytic nanoparticles inclusion and enzyme immobilization. This review aims to highlight key insights, practical limitations, and emerging strategies to improve catalyst reusability, stability, and scalability for real-world water treatment applications. Full article

Dendrons, also named dendritic wedges, are a kind of molecular tree, having a branched structure linked to a functional core. The functional core can be used in particular for the functionalization of materials. Different types of dendrons are known, synthesized either by a convergent process, from the external part to the core, or by a divergent process from the core to the external part. Polyphosphorhydrazone (PPH) dendrons are always synthesized by a divergent process, which enables a fine-tuning of both the core function and the external functions. They have been used for the functionalization of diverse materials such as silica, titanium dioxide, gold, graphene oxide, or different types of nanoparticles. Nanocomposites based on materials functionalized with PPH dendrons have been used in diverse fields such as catalysts, chemical sensors, for trapping pollutants, to support cell cultures, and against cancers, as will be emphasized in this review. Full article

The fundamental chemistries and electronic structures of platinum catalysts over nitrogen-doped carbon supports were examined to determine the subtle yet important roles graphitic defect-based and pyridinic defect-based nitrogen defects have in stabilizing platinum. These roles address and extend previously gathered incomplete knowledge of how combinations of graphitic defect and pyridinic defect affect the local electronic structure, leading to a greater unified understanding of platinum stability. A theoretical study was designed where different atomically sized platinum clusters were investigated over seven different nitrogen defect combinations on graphene carbon support. Differently sized platinum clusters offered parametric insights into the differences in metal–support interactions. Full article

Carbon materials, including graphene, carbon nanotubes, and fullerenes, serve as effective supports for catalysts and play a pivotal role in heterogeneous asymmetric catalysis due to their unique properties and ability to create defined environments for catalytic reactions. Recent research has focused on developing novel carbon-based catalysts that combine the advantages of heterogeneous catalysis with enhanced stability and reusability. This review highlights the synthesis and catalytic applications of graphene, carbon nanotubes, and fullerenes as heterogeneous support materials in asymmetric organocatalytic and organometallic reactions, covering their mechanisms, efficiency, and potential for advancing sustainable chemical processes. Full article

The overconsumption of fossil energy sources has resulted in serious environmental impacts and an ensuing energy crisis. Therefore, the search for a new alternative energy technology has become a focus of attention. The long-established Fischer–Tropsch synthesis technology and the recent CO₂ hydrogenation technology with unlimited potential seem to be among the ways to solve the above problems. Among them, the development of efficient Fe-based catalysts has become a key issue. Weaker interactions on carbon supports are more favourable for the formation of active phases in Fe-based catalysts than stronger metal–support interactions on conventional oxide supports. In this work, we systematically summarise the application of various types of carbon materials (carbon nanotubes, mesoporous carbon, graphene, activated carbon, etc.) in CO_x hydrogenation reactions. The effects of different structural types of carriers on the dispersion of active sites are discussed. At the same time, the effects of different carrier preparation methods on catalytic performance are compared. In addition, the role of surface modifications to carbon materials in the promotion of active sites is discussed. Finally, we propose possible research directions based on the current problems in these catalytic systems. The aim is to provide a reference for the development of new carbon materials and their application in CO_x hydrogenation. Full article

Ru-based catalysts manifest unparalleled hydrogen evolution reaction (HER) performance, but the hydrolysis of Ru species and the accumulation of corresponding reaction intermediates greatly limit HER activity and stability. Herein, Ru nanoparticle assemblies modified with single Mo atoms and supported on N-incorporated graphene (referred to as MoRu-NG) are compounded via hydrothermal and chemical vapor deposition (CVD) methods. The incorporation of single Mo atoms into Ru lattices modifies the local atomic milieu around Ru centers, significantly improving HER catalytic behavior and stability. More specifically, MoRu-NG achieves overpotentials of 53 mV and 28 mV at 10 mA cm⁻², with exceptional stability in acidic and alkaline seawater solutions, respectively. In MoRu-NG, Ru atoms have a special electronic structure and thus possess optimal hydrogen adsorption energy, which indicates that excellent HER activity mainly hinges upon Ru centers. To be specific, the d-electron orbitals of Ru atoms are close to half full, giving Ru atoms moderate bond energy for the assimilation and release of hydrogen, which is beneficial for the conversion of reaction intermediates. Moreover, the incorporation of single Mo atoms facilitates the formation of O and O’-bidentate ligands, significantly enhancing the structural stability of MoRu-NG in universal-pH seawater electrolysis. This work advances a feasible construction method of hexagonal octahedral configuration (Ru-O-Mo-N-C) and provides a route to synthesize an efficient and stable catalyst for electrocatalytic HER in universal-pH seawater. Full article

This study explores the selective hydrogenation of cinnamaldehyde using a series of metal catalysts supported on reduced graphene oxide (rGO) and conventional activated carbon (AC). Catalysts based on Pt, Pd, Rh, Ru, and Co were synthesized with controlled metal loading and characterized by XRD, SEM-EDS, XRF, and TEM. Among all tested materials, Pd supported on rGO synthesized via the Tour method (Pd/rTOGO) exhibited the highest catalytic activity, achieving 62% conversion of cinnamaldehyde and superior selectivity toward hydrocinnamaldehyde (HCAL). The support material had a significant influence on performance, especially for Pd catalysts, where 2D rGO outperformed 3D AC in both conversion and selectivity. In contrast, other metals (Pt, Rh, Ru, Co) showed only modest activity and limited selectivity tuning via support choice. Notably, GC-MS analysis revealed the formation of a previously underreported side product, 3-isopropoxy-propan-1-yl benzene (ether), likely formed via reductive etherification in isopropanol. The combined kinetic and selectivity data enabled the proposal of reaction pathways, including rapid transformation of cinnamylalcohol (COL) to hydrocinnamal alcohol (HCOL) and HCAL to ether. These findings emphasize the importance of support structure and surface functionality, particularly in 2D carbon materials, for designing efficient and selective hydrogenation catalysts. Full article

Producing hydrogen by water electrolysis has attracted significant attention as a potential renewable energy solution. In this work, a catalyst with reduced graphene oxide (rGO) loaded on IrO₂/TiO₂ (called rGO/IrO₂/TiO₂) was designed for the catalytic oxygen evolution reaction (OER). The catalyst was synthesized by coating graphene oxide onto a pretreated IrO₂/TiO₂ precursor, followed by thermal treatment at 450 °C to achieve reduction and the adhesion of graphene to the substrate. The graphene support retained its intact sp² carbon framework with minor oxygen-containing functional groups, which enhanced electrical conductivity and hydrophilicity. Benefiting from the synergistic effect of an rGO, IrO₂, and TiO₂ matrix, the rGO/IrO₂/TiO₂ catalyst only needed overpotentials of 240 mV and 320 mV to reach 10 mA cm⁻² and 100 mA cm⁻² in the OER, along with excellent stability over 50 h. Its morphology and crystalline structure were characterized by SEM and XRD spectroscopy, and its electrochemical performance was tested by LSV analysis, EIS impedance spectrum, and double-layer capacitance (C_dl) measurements. This work introduces an innovative and eco-friendly strategy for constructing a high-performance, functionalized Ir-based catalyst. Full article

The design of efficient and cost-effective electrocatalysts to replace Pt in an oxygen reduction reaction (ORR) is crucial for advancing proton exchange membrane fuel cell (PEMFC) technologies. This study synthesized Pd-Co bimetallic alloy nanoparticles supported on reduced graphene oxide (rGO) through a simple chemical-reduction method, making it suitable for low-cost, large-scale fabrication and significantly reducing the need for Pt. The nanostructures were systematically characterized using various analytical techniques, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). Electrochemical investigations revealed that the Pd-Co/rGO catalyst exhibits remarkable ORR performance in an alkaline environment, with an electrode-area-normalized activity rivaling that of the commercial Pt/C catalyst. Remarkably, Pd-Co/rGO demonstrated an onset potential (E_onset) of 0.944 V (vs. RHE) and a half-wave potential (E_1/2) of 0.782 V (vs. RHE), highlighting its excellent ORR activity. Furthermore, the Pd-Co/rGO catalyst displayed superior methanol-tolerant ORR activity, outperforming Pt/C and monometallic Pd/rGO and Co/rGO systems. The enhanced electrocatalytic performance is attributed to the smallest size, consistent shape, and good dispersion of the alloy structure on the RGO surface. These findings establish Pd-Co/rGO as a promising alternative to Pt-based catalysts, addressing key challenges such as methanol crossover while advancing PEMFC technology in alkaline media. Full article

Pt on carbon black (Pt/C) has been widely used as a catalyst for both ORR and hydrogen oxidation reaction (HOR), but its stability is compromised due to carbon corrosion and catalyst poisoning, leading to low Pt utilization. To address this issue, this study suggests replacing carbon black with graphene in the catalyst layer. The importance of this work lies in the detailed examination of novel electrocatalysts with high electrocatalytic activity for large-scale power generation. In this paper, we discuss the use of regulatory techniques like structure tuning and composition optimization to construct nanocatalysts impregnated with noble and non-noble metals on graphene supports. Finally, it highlights the limitations and advantages of these nanocatalysts along with some future perspectives. Our objective is that this summary will help in the research and rational design of graphene-based nanostructures for efficient ORR electrocatalysis. The results of this study showed that the performances of graphene-based catalysts show high electrochemical active surface areas for Pt-Fe/GNPs and Pt-Ni/GNPs catalysts (132 and 136 m² g⁻¹, respectively) at 100 operating cycles. Also, high current densities and power densities were observed for Pt₃-Ni/G and Pt-Co/G catalysts used at the cathode. The values for current density were 1.590 and 1.779 A cm⁻², respectively, while the corresponding values for power density were 0.57 and 0.785 W cm⁻². Full article

Ni nanoparticles supported on graphene-based materials were tested as catalysts for the oxygen reduction reaction (ORR) to be used in anion exchange membrane fuel cells (AEMFCs). The introduction of N into the graphene structure produced an enhancement of electrocatalytic activity by improving electron transfer and creating additional active sites for the ORR. Materials containing both N and S demonstrated the highest stability, showing only a 3% performance loss after a 10 h stability test and therefore achieving the best overall performance. This long-term durability is attributed to the synergetic effect of Ni nanoparticles and bi-doped (S/N)-reduced graphene oxide. The findings suggest that the strategic incorporation of both nitrogen and sulphur into the graphene structure plays a crucial role in optimising the electrocatalytic properties of Ni-based catalysts. Full article

Carbon materials supported Fe-based catalysts possess great potential for the thermal-catalytic hydrogenation of CO₂ into valuable chemicals, such as alkenes and oxygenates, due to the excellent active sites’ accessibility, appropriate interaction between the active site and carbon support, as well as the excellent capacities in C-O bond activation and C-C bond coupling. Even though tremendous progress has been made to boost the CO₂ hydrogenation performance of carbon-supported Fe-based catalysts, e.g., additives modification, the choice of different carbon materials (graphene or carbon nanotubes), electronic property tailoring, etc., the effect of carbon support porosity on the evolution of Fe-based active sites and the corresponding catalytic performance has been rarely investigated. Herein, a series of porous carbon samples with different porosities are obtained by the K₂CO₃ activation of petroleum pitch under different temperatures. Fe-based active sites and the alkali promoter Na are anchored on the porous carbon to study the effect of carbon support porosity on the physicochemical properties of Fe-based active sites and CO₂ hydrogenation performance. Multiple characterizations clarify that the bigger meso/macro-pores in the carbon support are beneficial for the formation of the Fe₅C₂ crystal phase for C-C bond coupling, therefore boosting the synthesis of C₂₊ chemicals, especially C₂₊ alcohols (C₂₊OH), while the limited micro-pores are unfavorable for C₂₊ chemicals synthesis owing to the sluggish crystal phase evolution and reactants’ inaccessibility. We wish our work could enrich the horizon for the rational design of highly efficient carbon-supported Fe-based catalysts. Full article

In the present investigation, Cu₂O-based composites were successfully prepared through a multistep method where cubic Cu₂O nanoparticles (CU Cu₂O) have been grown on Reduced Graphene Oxide (RGO) nanosheets. The structural and morphological properties of the materials have been studied through a comprehensive characterization, confirming the coexistence of crystalline Cu₂O and RGO. Microscopical imaging revealed the intimate contact between the two materials, affecting the size and the distribution of Cu₂O nanoparticles on the support. The features of the improved morphology strongly affected the electrochemical behavior of the composites, increasing the activity and the faradaic efficiencies towards the electrochemical CO₂ reduction reaction process. CU Cu₂O/RGO 2:1 composite displayed selective CO formation over H₂, with higher currents compared to pristine Cu₂O (−0.34 mA/cm² for Cu₂O and −0.64 mA/cm² for CU Cu₂O/RGO 2:1 at the voltage of −0.8 vs. RHE and in a CO₂ atmosphere) and a faradaic efficiency of 50% at −0.9 V vs. RHE. This composition exhibited significantly higher CO production compared to the pristine materials, indicating a favorable *CO intermediate pathway even at lower voltages. The systematic investigation on the effects of nanostructuration on composition, morphology and catalytic behavior is a valuable solution for the formation of effective interphases for the promotion of catalytic properties providing crucial insights for future catalysts design and applications. Full article

TiO₂-based mixed oxide–carbon composite support for Pt electrocatalysts provides higher stability and CO tolerance under the working conditions of polymer electrolyte membrane fuel cells compared to traditional carbon supports. Non-traditional carbon materials like graphene nanoplatelets and graphite oxide used as the carbonaceous component of the composite can contribute to its affordability and/or functionality. Ti_(1−x)Mo_xO₂-C composites involving these carbon materials were prepared through a sol–gel route; the effect of the extension of the procedure through a solvothermal treatment step was assessed. Both supports and supported Pt catalysts were characterized by physicochemical methods. Electrochemical behavior of the catalysts in terms of stability, activity, and CO tolerance was studied. Solvothermal treatment decreased the fracture of graphite oxide plates and enhanced the formation of a reduced graphene oxide-like structure, resulting in an electrically more conductive and more stable catalyst. In parallel, solvothermal treatment enhanced the growth of mixed oxide crystallites, decreasing the chance of formation of Pt–oxide–carbon triple junctions, resulting in somewhat less CO tolerance. The electrocatalyst containing graphene nanoplatelets, along with good stability, has the highest activity in oxygen reduction reaction compared to the other composite-supported catalysts. Full article

Some composite materials have been prepared, constituted by a cyclodextrin-bis-urethane-based nanosponge matrix in which a reduced graphene oxide/silver nanoparticles photocatalyst has been dispersed. Different chain extenders were employed for designing the nanosponge supports, in such a way as to decorate their hyper-cross-linked structure with diverse functionalities. Moreover, two different strategies were explored to accomplish the silver loading. The obtained systems were successfully tested as catalysts for the photodegradation of emerging pollutants such as model dyes and drugs. Enhancement of the photoactive species performance (up to nine times), due to the synergistic local concentration effect exerted by the nanosponge, could be assessed. Overall, the best performances were shown by polyamine-decorated materials, which were able to promote the degradation of some particularly resistant drugs. Some methodological issues pertaining to data collection are also addressed. Full article