Search Results (92)

The effects of Ce incorporation into trimetallic PtSnIn-supported catalysts were investigated for a propane dehydrogenation reaction with advanced characterization techniques. It was found that some Ce species exist in the form of CeAlO₃ on the reduced PtSnIn/xCe-Al catalyst, significantly enhancing the thermal stability of the alumina support. The NH₃-TPD measurements verified that the total acidity of the PtSnIn/xCe-Al catalysts decreases with the addition of Ce. The PtSnIn/1.5Ce-Al catalyst exhibits the optimal particle distribution with the smallest Pt particle size of 8.0 nm, which was revealed by TEM. The H₂-TPR and XPS results suggest that more oxidized-state Sn species form on catalyst surfaces, and the metal–support interaction can be strengthened when Ce is introduced. Furthermore, TG analysis demonstrates that Ce incorporation substantially reduces coke formation on the spent catalysts. The PtSnIn/1.5Ce-Al catalyst exhibits exceptional catalytic performance, achieving an initial propane conversion of 62.6% and maintaining a conversion of 57.2% after a 120 min reaction. In addition, the PtSnIn/1.5Ce-Al catalyst possesses high long-term stability. Over 40.0% propane conversion can be maintained after a 53 h continuous PDH reaction. These findings highlight the pivotal role of Ce in improving the structural properties and catalytic performance of PtSnIn-based catalysts for propane dehydrogenation, offering valuable insights for the design of highly efficient and stable dehydrogenation catalysts. Full article

The electrocatalytic hydrogenation (ECH) of biomass-derived phenolic compounds is a promising approach to the production of value-added chemicals and biofuels in a sustainable way under moderate reaction conditions. This study provides a comprehensive comparison of electrochemical and thermochemical hydrogenation processes, highlighting their relative advantages in terms of energy efficiency, product selectivity, and environmental impact. Several electrocatalysts (Pt, Pd, Rh, Ru), membranes (Nafion, Fumasep, GO-based PEMs), and reactor configurations are tested for the selective conversion of model compounds such as phenol, guaiacol, furfural, and levulinic acid. The contributions made by the electrode material, electrolyte composition, membrane nature, and reaction conditions are critically evaluated in relation to Faradaic efficiency, conversion rates, and product selectivity. The enhancement in the performance achieved by a new catalyst architecture is emphasized, such as MOF-based systems and bimetallic/trimetallic catalysts. In addition, a demonstration of graphite-based membranes and membrane-separated slurry reactors (SSERs) is provided, for enhanced ion transport and reaction control. The results illustrate the potential of using ECH as a low-carbon, scalable, and tunable method for the upgrading of biomass. This study offers valuable insights and guidelines for the rational design of next-generation electrocatalytic systems toward green chemical synthesis and emphasizes promising perspectives for the strategic development of electrochemical technologies in the pathway of a sustainable energy economy. Full article

As the energy crisis and environmental pollution continue to intensify, the demand for clean energy has increased. Using two-dimensional materials to catalyze overall water splitting is an important pathway for clean energy production. This study investigated the catalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) of tri-atomic clusters supported on a two-dimensional material, graphenylene (GPN). The structural stability of GPN was thoroughly investigated, and materials were employed as substrates to support a series of 28 distinct trimer clusters composed of 3d, 4d, and 5d transition metals. Ideal combinations of these systems were screened and designed. The loading configurations of TM₃@GPN in two different systems were systematically studied. The stability of the catalyst was assessed by calculating the binding and cohesive energies and by performing molecular dynamics simulations, to confirm the catalyst stability. The optimal bifunctional catalysts for overall water splitting were identified as Au₃@GPN, Pt₃@GPN, and Pd₃@GPN, all of which demonstrated superior overall water splitting performance. As a novel two-dimensional material, biphenylene-based materials, when used to support metal clusters as bifunctional catalysts for water splitting, represent an efficient and innovative approach. Full article

The development of advanced electrocatalysts plays a pivotal role in enhancing hydrogen production through water electrolysis. In this study, we employed a two-step electrodeposition method to fabricate a 3D porous Cu-Co-Ni alloy with superior catalytic properties and long-term stability for hydrogen evolution reaction (HER). The resulting trimetallic alloy, Cu@Cu-Ni-Co, demonstrated significant improvements in structural integrity and catalytic performance. A comparative analysis of electrocatalysts, including Cu, Cu@Ni-Co, and Cu@Cu-Ni-Co, revealed that Cu@Cu-Ni-Co achieved the best results in alkaline media. Electrochemical tests conducted in 1.0 M NaOH showed that Cu@Cu-Ni-Co reached a current density of 10 mA cm⁻² at a low overpotential of 125 mV, along with a low Tafel slope of 79.1 mV dec⁻¹. The catalyst showed exceptional durability, retaining ~95% of its initial current density after 120 h of continuous operation at high current densities. Structural analysis confirmed that the enhanced catalytic performance arises from the synergistic interaction between Cu, Ni, and Co within the well-integrated trimetallic framework. This integration results in a large electrochemical active surface area (ECSA) of 380 cm² and a low charge transfer resistance (15.76 Ω), facilitating efficient electron transfer and promoting superior HER activity. These findings position Cu@Cu-Ni-Co as a highly efficient and stable electrocatalyst for alkaline HER in alkaline conditions. Full article

This study focuses on making non-precious electrocatalysts for improving the performance of Direct Alcohol Fuel Cells (DAFCs). Specifically, it examines the oxidation of ethanol and methanol. Conventional platinum-based catalysts are expensive and suffer from problems such as degradation and poisoning. To overcome these challenges, we fabricated tri-metallic catalysts composed of nickel, cobalt, and titanium dioxide (TiO₂) embedded in carbon nanofibers (CNFs). The synthesis included electrospinning and subsequent carbonization as well as optimization of parameters to achieve uniform nanofiber morphology and high surface area. Electrochemical characterization revealed that the incorporation of TiO₂ significantly improved electrocatalytic activity for ethanol and methanol oxidation, with current densities increasing from 57.8 mA/cm² to 74.2 mA/cm² for ethanol and from 38.69 mA/cm² to 60.39 mA/cm² for methanol as the TiO₂ content increased. The catalysts showed excellent stability, with the TiO₂-enriched sample (T2) showing superior performance during longer cycling tests. Chronoamperometry and electrochemical impedance spectroscopy are used to examine the stability of the catalysts and the dynamics of the charge carriers. Impedance spectroscopy indicated reduced charge transfer resistance, confirming enhanced activities. These findings suggest that the synthesized non-precious electrocatalysts can serve as effective alternatives to platinum-based materials, offering a promising pathway for the development of cost-efficient and durable fuel cells. Research highlights non-precious metal catalysts for sustainable fuel cell technologies. Full article

Hollow flower-like multi-metallic nanocrystals have attracted significant research attention due to their exceptional catalytic properties, which stem from their high surface area-to-volume ratio and abundant active sites. Nevertheless, conventional synthesis methods for noble metal nanocrystals typically involve complex procedures or require harsh reaction conditions. In this work, we developed a facile and environmentally benign strategy for fabricating hollow flower-shaped trimetallic nanocrystals at ambient temperature. Our approach employs AgCl nanocubes, derived from AgNO₃ and HAuCl₄, as self-sacrificing templates. Through ascorbic acid-mediated reduction of metal precursors, we successfully synthesized three distinct types of hollow flower-like nanocrystals: AuAgCu, AuAgPt, and AuAgPd. Comprehensive characterization confirmed the well-defined morphology and precise composition control of the as-prepared nanocrystals. The catalytic performance was systematically evaluated through in situ UV–vis spectroscopy monitoring of 4-nitrophenylthiophenol reduction, revealing the following activity trend: AuAgCu > AuAgPt > AuAgPd. This study not only provides a versatile platform for constructing sophisticated multi-metallic nanostructures but also offers valuable insights into the structure–activity relationship of complex catalysts. Full article

Chemical sensors, relying on electrical conductance changes in a gas-sensitive material due to the surrounding gas, have the (dis-)advantage of reacting with multiple target gases and humidity. In this work, we report CMOS-integrated SnO₂ thin film-based gas sensors, which are functionalized with mono-, bi-, and trimetallic nanoparticles (NPs) to optimize the sensor performance. The spray pyrolysis technology was used to deposit the metal oxide sensing layer on top of a CMOS-fabricated micro-hotplate (µhp), and magnetron sputtering inert-gas condensation was employed to functionalize the sensing layer with metallic NPs, Ag-, Pd-, and Ru-NPs, and all combinations thereof were used as catalysts to improve the sensor response to carbon monoxide and to suppress the cross-sensitivity toward humidity. The focus of this work is the detection of toxic carbon monoxide and a specific hydrocarbon mixture (HC_mix) in a concentration range of 5–50 ppm at different temperatures and humidity levels. The use of CMOS chips ensures low-power, integrated sensors, ready to apply in cell phones, watches, etc., for air quality-monitoring purposes. Full article

A huge variety of chemical commodities are built from propylene molecules, and its conventional production technologies (naphtha steam cracking and fluid catalytic cracking) are unable to satisfy C₃H₆’s increasing requirements. In this scenario, Direct Propane Dehydrogenation (PDH) provides a practical and reliable route for supplying this short demand due to the economic availability of the raw material (C₃H₈) and the high propylene selectivities. The main challenges of propane dehydrogenation technology are related to the design of very active catalysts with negligible byproduct formation. In particular, the issue of catalyst deactivation by coke deposition still requires further development. In addition, PDH is a considerable endothermic reaction, and the efficiency of this technology is strictly related to heat transfer management. Thus, this current review specifically discusses the recent advances in highly dispersed bimetallic and trimetallic catalysts proposed for the PDH reaction in both conventional-heated and microwave-heated reactors. From the point of view of catalyst development, the recent research is mainly addressed to obtain nanometric and single-atom catalysts and core–shell alloys: atomically dispersed metal atoms promote the desorption of surface-bonded propylene and inhibit its further dehydrogenation. The discussion is focused on the alternative formulations proposed in the last few years, employing active species and supports different from the classical Pt-Sn/Al₂O₃ catalyst. Concerning the conventional route of energy-supply to the catalytic bed, the advantage of using a membrane as well as fluidized bed reactors is highlighted. Recent developments in alternative microwave-assisted dehydrogenation (PDH) employing innovative catalytic systems based on silicon carbide (SiC) facilitate selective heating of the catalyst. This advancement leads to improved catalytic activity and propylene selectivity while effectively reducing coke formation. Additionally, it promotes environmental sustainability in the ongoing electrification of chemical processes. Full article

The catalytic dehydrogenation of NaBH₄ for the generation of H₂ has a lot of potential as a reliable and achievable approach to make H₂, which could be used as a safe and cost-effective energy source in the near future. This work describes the production of unique trimetallic NiCrPd-decorated carbon nanofiber (NiCrPd-decorated CNF) catalysts using electrospinning. The catalysts demonstrated exceptional catalytic activity in generating H₂ through NaBH₄ dehydrogenation. The catalysts were characterized using SEM, XRD, TEM, and TEM-EDX analyses. NiCrPd-decorated CNF formulations have shown higher catalytic activity in the dehydrogenation of NaBH4 compared with NiCr-decorated CNFs. It is likely that the better catalytic performance is because the three metals in the NiCrPd-decorated CNF structure interact with each other. Furthermore, the NiCrPd-decorated CNFs catalyzed the dehydrogenation of NaBH₄ with an activation energy (E_a) of 26.55 KJ/mol. The kinetics studies showed that the reaction is first-order dependent on the dose of NiCrPd-decorated CNFs and zero-order dependent on the concentration of NaBH₄. Full article

A mixed-metal ternary chalcogenide, cobalt molybdenum telluride (CMT), has been identified as an efficient tri-functional electrocatalyst for seawater splitting, leading to enhanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR). The CMT was synthesized by a single step hydrothermal technique. Detailed electrochemical studies of the CMT-modified electrodes showed that CMT has a promising performance for OER in the simulated seawater solutions, exhibiting a small overpotential of 385 mV at 20 mA cm⁻², and superior catalyst durability for prolonged period of continuous oxygen evolution. Interestingly, while gas chromatography analysis confirmed the evolution of oxygen in an anodic chamber, it showed that there was no chlorine evolution from these electrodes in alkaline seawater, highlighting the novelty of this catalyst. CMT also displayed remarkable ORR activity in simulated seawater as indicated by its four-electron reduction pathway forming water as the dominant product. One of the primary challenges of seawater splitting is chlorine evolution from the oxidation of dissolved chloride salts. The CMT catalyst successfully and significantly lowers the water oxidation potential, thereby separating the chloride and water oxidation potentials by a larger margin. These results suggest that CMT can function as a highly active tri-functional electrocatalyst with significant stability, making it suitable for clean energy generation and environmental applications using seawater. Full article

Despite considerable progress, high-performing durable catalysts operating under large current densities (i.e., >1000 mA/cm²) are still lacking. To discover platinum group metal-free (PGM-free) electrocatalysts for sustainable energy, our research involves investigating layered topological magnetic materials (semiconducting ferromagnets) as highly efficient electrocatalysts for the hydrogen evolution reaction under high current densities and establishes the novel relations between structure and electrochemical property mechanisms. The materials of interest include transition metal trihalides, i.e., CrCl₃, VCl₃, and VI₃, wherein a structural unit, the layered structure, is formed by Cr (or V) atoms sandwiched between two halides (Cl or I), forming a tri-layer. A few layers of quantum crystals were exfoliated (~50−60 nm), encapsulated with graphene, and electrocatalytic HER tests were conducted in acid (0.5M H₂SO₄) and alkaline (1M KOH) electrolytes. We find a reasonable HER activity evolved requiring overpotentials in a range of 30–50 mV under 10 mA cm⁻² and 400−510 mV (0.5M H₂SO₄) and 280−500 mV (1M KOH) under −1000 mA cm⁻². Likewise, the Tafel slopes range from 27 to 36 mV dec⁻¹ (Volmer–Tafel) and 110 to 190 mV dec⁻¹ (Volmer–Herovsky), implying that these mechanisms work at low and high current densities, respectively. Weak interlayer coupling, spontaneous surface oxidation, the presence of a semi-oxide subsurface (e.g., O–CrCl₃), intrinsic Cl (or I) vacancy defects giving rise to in-gap states, electron redistribution (orbital hybridization) affecting the covalency, and sufficiently conductive support interaction lowering the charge transfer resistance endow the optimized adsorption/desorption strength of H^* on active sites and favorable electrocatalytic properties. Such behavior is expedited for bi-/tri-layers while exemplifying the critical role of quantum nature electrocatalysts with defect sites for industrial-relevant conditions. Full article

The urgency of water remediation and the conversion of toxic pollutants into non-toxic compounds is increasingly crucial in our industrialized world. Heterogeneous catalysts based on metal nanoparticles, which are cost-effective, non-toxic, and readily available, have garnered significant attention in the market due to their unique catalytic properties. This study presents sol–gel-based hybrid silica matrices that encapsulate nickel, designed for the efficient reductive de-halogenation of tri-bromoacetic acid (TBAA), di-bromoacetic acid (DBAA), mono-bromoacetic acid (MBAA), tri-chloroacetic acid (TCAA), mono-chloroacetic acid (MCAA), and Chloroacetanilide (CAA). A detailed study of the product distribution from each halo-acetic acid (HAA) is presented. The study points out that other products are formed from Ni-catalyzed reduction reactions of HAAs, breaking the conventional rules of stepwise reduction mechanisms. The plausible mechanisms of the catalytic processes are discussed. Full article

New flower-shaped metallophthalocyanine polymers (THB-4-M, M = Co, Cu) have been synthesized by using 1,3,5-Tri(4-hydroxyphenhyl) benzene (THB) as rigid and contorted units to control the morphology under the solvothermal method. The polymers were characterized using FT-IR, UV-vis, SEM, TGA, and XPS. These polymers were applied as heterogeneous catalysts for the chemical fixation of carbon dioxide (CO₂) to cyclic carbonates without solvent. The influence of reaction parameters and different metal centers on the catalytic performance were studied in detail. Under optimal conditions, the catalysts showed high conversion (49.9–99.0%), selectivity (over 85%), and reusability at ambient conditions (at 1 bar CO₂). Full article

In the context of water electrolysis being highlighted as a promising technology for the large-scale sustainable production of hydrogen, the water-splitting electrocatalytic properties of an asymmetrically functionalized A₃B zinc metalated porphyrin, namely, Zn(II) 5-(4-pyridyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin, were evaluated in a wide pH range. Two different electrode manufacturing procedures were employed to outline the porphyrin’s applicative potential for the O₂ and H₂ evolution reactions (OER and HER). The electrode, manufactured by coating the catalyst on a graphite support from a dimethylsulfoxide solution, displayed electrocatalytic activity for the OER in an acidic electrolyte. An overpotential value of 0.44 V (at i = 10 mA/cm²) and a Tafel slope of 0.135 V/dec were obtained. The modified electrode that resulted from applying a Zn(II)-porphyrin-containing catalyst ink onto the same substrate type was identified as a bifunctional water-splitting catalyst in a neutral medium. OER and HER overpotentials of 0.78 and 1.02 V and Tafel slopes of 0.39 and 0.249 V/dec were determined. This is the first Zn(II)-porphyrin to be reported as a heterogenous bifunctional water-splitting electrocatalyst in neutral aqueous electrolyte solution and is one of very few porphyrins behaving as such. The TEM analysis of the porphyrin’s self-assembly behavior revealed a wide variety of architectures. Full article

Effluent-containing dye molecules is a significant environmental hazard. An economical and energy-saving solution is needed to combat this issue for the purpose of environmental sustainability. In this study, Fe-Ni-Co-based trimetallic nanocomposite was synthesized using the coprecipitation method. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infra-Red spectroscopy were conducted to explore the physical morphology, phase structure and functional groups of the synthesized catalyst. Among dyes, methyl orange is considered as a major contaminant in textile effluent. The current study focused on the degradation of methyl orange using a trimetallic Fe-Ni-Co-based nanocomposite. A central composite design in response surface methodology was employed to analyze the independent variables including dye concentration, catalyst dose, temperature, hydrogen peroxide, irradiation time, and pH. Dye degradation has been achieved up to 81% in 20 min at the lowest initial concentration (5 mg/L) in optimized conditions. Based on ANOVA, the predicted values were in great agreement with the actual values, signifying the applicability of response surface methodology in the photocatalytic decolorization of dyeing effluents. The results gained from this research demonstrated that the synthesis method of trimetallic nanocomposite (Iron Triad) is a cost-effective and energy efficient method that can be scaled up to a higher level for industrial application. Full article