Search Results (693)

Developing cost-effective alternatives to platinum-based catalysts remains paramount for commercializing anion exchange membrane fuel cells (AEMFCs). We report a metal-free nitrogen-doped carbon catalyst derived from a rationally designed polyurea–polyimine copolymer that outperforms commercial 20 wt% Pt/C in superior relative durability and methanol tolerance. Strategic integration of polyurea’s pore-forming capability with polyimine’s thermal stability enabled the synthesis of a catalyst (NC-1000N) featuring ultrahigh surface area (1276.5 m² g⁻¹), optimal nitrogen speciation (20.5% pyridinic-N, 45.3% graphitic-N), and enhanced graphitization, which improves the electrical conductivity of catalysts. NC-1000N exhibited exceptional oxygen reduction performance with an onset potential of 0.96 V, almost four-electron selectivity (n = 3.87), a medium Tafel slope (105 mV dec⁻¹), and minimal charge transfer resistance (46.74 Ω). When evaluated in single-cell AEMFCs, NC-1000N delivered a peak power density of 372.1 mW cm⁻², which is 26% higher than Pt/C at equivalent loading, while demonstrating superior stability (94.8% retention after 7 h) and complete methanol tolerance. Systematic pyrolysis temperature optimization (800–1000 °C) revealed critical structure–property relationships governing catalyst evolution from disordered precursor to highly graphitic, nitrogen-enriched carbon with precisely engineered active sites. This work establishes polymer-derived carbons and provides design principles for scalable synthesis of high-performance metal-free electrocatalysts for sustainable energy conversion technologies. Full article

Hydrogen (H₂) has emerged as a promising next-generation energy carrier with significant potential to mitigate climate change and environmental pollution. The hydrogen evolution reaction (HER) is the critical half-reaction directly responsible for hydrogen production. Efficient HER electrocatalysts must exhibit low overpotential values and fast reaction kinetics to achieve high catalytic performance. While platinum (Pt) remains the benchmark catalyst due to its ideal hydrogen adsorption energy, high electrical conductivity, and superior chemical stability, further innovations are essential. This review summarizes recent advances in Pt-based HER catalysts, focusing on two primary design strategies: metal-level engineering and support-level engineering. These approaches allow for precise control over electronic structures, active site distributions, and interfacial properties, paving the way for next-generation HER electrocatalysts. Full article

This paper presents the results of an experimental investigation of woody biomass combustion under real operating conditions of a heating boiler equipped with an integrated platinum-promoted oxidation catalyst (Pt-OX) and vanadium-based catalytic reactor (V-CAT) system for pollutant emission reduction, particularly nitrogen oxides (NO_x). Various configurations of the catalytic flue gas treatment system were investigated, including single-stage, dual-stage, and multi-stage vanadium- and platinum-based catalytic reactor arrangements. The investigated system incorporated platinum-promoted oxidation catalysts and a vanadium-based monolithic catalytic reactor. No external ammonia or urea injection was applied during the experimental campaign. Therefore, the catalytic system was evaluated under realistic biomass combustion conditions involving nitrogen-containing species naturally generated during fuel conversion processes. The obtained thermal and emission parameters were compared with those recorded during boiler operation without catalytic treatment. The investigated catalytic configurations significantly reduced pollutant emissions, with the highest-performing arrangement decreasing NO emissions from 112 ppm to 11 ppm, corresponding to a reduction efficiency exceeding 90%. The results demonstrate the potential of integrated catalytic reactor systems for improving the environmental performance of small-scale biomass-fired heating units operating under real conditions. Full article

Platinum group metals (PGMs: Pt, Pd, Rh, Ru, Os, Ir) are critical strategic metals. Spent automotive catalysts (SACs) represent one of the most significant secondary sources of PGMs, and their recovery is essential for alleviating the supply–demand imbalance. In the recycling chain, pyrometallurgical processing of SACs generates Fe-Si-based alloy concentrates (termed Fe−Si−PGMs), serving as an important yet challenging intermediate resource for PGM recovery. This review first summarizes the pyrometallurgical and hydrometallurgical processes used for recovering PGMs from SACs, before shifting its focus to the treatment technologies for PGMs in Fe–Si–PGMs alloy. These techniques, including direct extraction, extraction following desilication (via alkaline roasting, slagging, or hydrometallurgical routes), and in situ mechanochemical extraction, are critically evaluated in terms of their advantages and limitations. Furthermore, given that the accurate quantification of trace-level yet high-value PGMs represents another key challenge in the recovery chain due to complex sample matrices, this work systematically outlines and compares the analytical methods commonly employed, such as fire assay, spectroscopic and mass spectrometric techniques, electrochemical methods, and alkali fusion. Finally, several recommendations are provided regarding PGM recovery from SACs, with emphasis on Fe−Si−PGMs alloy processing and analytical methods for PGMs. Full article

The electrochemical performance of hydrogen compressors (EHCs) depends critically on the hierarchical microstructure of their catalyst layers (CLs), where platinum, carbon, and ionomer phases govern coupled charge and mass transport across nanometric (Nano) and mesoporous (Meso) scales, the latter characterized by agglomerate and pore phases. This work presents an experimental–computational framework to establish quantitative microstructure–transport–performance relationships in EHC CLs. CLs were fabricated by electrospray deposition on Nafion^® 117 membranes and characterized by scanning electron microscopy, from which 33 representative Meso MCs were extracted and used to assemble an EHC cell for experimental polarization curves. Statistically equivalent Nano MCs resolved phase connectivity within the agglomerate phase and determined the effective catalyst area from neighboring phase configurations. Effective transport coefficients for electronic conductivity, protonic conductivity, and H₂ diffusivity were computed via the finite volume method and multiscale-coupled into an analytical polarization model. Electronic and protonic conductivities are controlled by conductive-phase connectivity at the Nano scale, while H₂ diffusivity is governed by the pore fraction and spatial distribution at the Meso scale, with variations exceeding three orders of magnitude. Multiscale transport coupling factors obtained via inverse calibration reduced model–experiment discrepancies to 0.05 V, validating the framework for EHC electrode design. Full article

The development of sustainable technologies capable of simultaneously addressing environmental pollution and renewable energy production remains a major scientific challenge. In this work, titanium dioxide nanoparticles (GTiO₂) were synthesized through a plant-extract-assisted route using Punica granatum (pomegranate) peel extract and subsequently modified with platinum nanoparticles (Pt NPs) to obtain an efficient photocatalyst for the photoreforming of organic pollutants. The resulting Pt-GTiO₂ material exhibited an anatase crystal structure with an average crystallite size of approximately 12 nm and a specific surface area of about 140 m² g⁻¹. Comprehensive characterization using XRD, BET, TEM, FTIR, Raman, and photoluminescence spectroscopy (PL) revealed favorable structural and optoelectronic properties that promote efficient charge separation. The photocatalytic performance of Pt-GTiO₂ was evaluated through the simultaneous degradation of 2-naphthol, a priority aromatic pollutant, and hydrogen evolution under simulated solar irradiation in anaerobic conditions. Under the investigated conditions, Pt-GTiO₂ effectively promoted 2-naphthol degradation, with substantial but incomplete mineralization, as confirmed by TOC removal. The synthesized catalyst showed degradation efficiency higher than Pt-UV100 and comparable to Pt-P25, while exhibiting superior hydrogen evolution when compared with Pt-P25. Mechanistic investigations combining scavenger experiments, electron paramagnetic resonance (EPR) spectroscopy, and the identification of reaction intermediates suggest that photogenerated holes play a major role in the initial oxidation step under the mechanistic test conditions. The detected intermediates indicate that photoreforming proceeds via multiple pathways, including hydroxylation, ring-opening, reduction, and fragmentation. These findings highlight the potential of biogenic TiO₂-based photocatalysts for converting hazardous organic pollutants into clean hydrogen fuel while simultaneously achieving wastewater purification, offering a promising route toward sustainable environmental and energy technologies. Full article

Developing low-cost, non-noble-metal electrocatalysts to replace platinum-based benchmarks for the alkaline hydrogen evolution reaction (HER) remains a critical challenge. Using density functional theory (DFT) calculations combined with the computational hydrogen electrode (CHE) model, we systematically investigate the thermodynamics, kinetics, and intrinsic reaction mechanism of HER on a TiO₂-supported Ni₃ trimer (Ni₃/TiO₂) in alkaline media. We find that the Ni₃ trimer, rather than the TiO₂ support, provides multiple active sites for intermediate adsorption. The trimeric Ni₃ motif generates delocalized electronic states, leading to electron-rich active sites that significantly lower the barrier for water dissociation, facilitate intermediate desorption, and sustain catalytic turnover. The reaction proceeds predominantly via the Volmer–Heyrovsky pathway, where either water dissociation or H₂ desorption can be the rate-determining step, depending on the applied potential. Crucially, the significantly reduced reaction barrier heights demonstrate that the alkaline HER activity of Ni₃/TiO₂ is comparable to that of benchmark Pt₁/TiO₂ single-atom catalysts (SACs). This work establishes a promising design strategy for constructing high-performance non-noble metal few-atom catalysts (FACs) to replace noble metal SACs for multi-step electrocatalytic reactions. Full article

Fuel cells are regarded as highly promising energy devices due to their clean and efficient energy conversion characteristics. However, their core material, platinum-based catalysts face challenges such as high cost, resource scarcity, and the high energy consumption and pollution associated with traditional synthesis methods, which contradict the green development principles of fuel cell technology. The rise of green chemistry provides a new research direction for developing environmentally friendly and cost-effective catalyst preparation routes. This review systematically summarizes recent research progress in the green synthesis of platinum-based catalysts for fuel cells, focusing on four core strategies: green solvent systems, biological reduction systems, renewable resource templates, and green energy-saving methods. It provides a detailed analysis of the principles of each method and their regulatory mechanisms on the microstructure. More importantly, this review elucidates the effects of size, morphology, and surface state on catalytic performance and establishes a structure–activity relationship linking green synthesis methods, microstructure, and catalytic performance and further discusses the regulatory mechanisms of catalyst structure, operating temperature, and electrolyte environment on electrochemical kinetic behavior. Furthermore, this article critically evaluates the advantages, limitations, and industrialization challenges of various green technologies. This review provides an important reference for the preparation and industrial application of high-performance, low-platinum, and environmentally friendly fuel cell catalysts. Full article

The CNT-supported nanodispersed Pt–Mo catalysts for the ethanol electrooxidation reaction in the alkaline solution are synthesized and their characteristics are studied. Based on the XPS studies in a wide range of platinum content (10–40 wt %), it is found that in the composition of the catalysts, platinum is predominantly in the metallic state, and molybdenum is in the hexavalent form, probably in the form of MoO₃ oxide. According to the XRD and electrochemical studies, the Pt/CNT and PtMo/CNT catalysts with equal platinum contents (~20 wt %) are characterized by similar platinum crystallite sizes (5–10 nm) and electrochemically accessible surface areas (23–26 m²/g_Pt). This indicates that platinum is not shielded by the molybdenum compounds. When the platinum content increases above 20 wt %, the Pt:Mo atomic ratio increases (the nominal ratio is 1:1), which may be due to the decoration of molybdenum oxide with platinum nanoparticles. A study of the kinetics of the ethanol electrooxidation reaction showed that the activity of the PtMo/CNT system is higher than that of the Pt/CNT catalyst. However, the efficiency of platinum use decreases as its content in the PtMo/CNT system increases from 10 to 40 wt %. On the other hand, the systems containing 20–40 wt % Pt exhibit the highest activity per unit catalyst weight, making them very promising for use as a component of the anode active layer of a fuel cell. The tests of the alkaline ethanol fuel cell based on the synthesized catalysts show the maximum power density of 29 mW/cm², which corresponds to the level of the best literature parameters under similar experimental conditions. Full article

Platinum group metals (PGMs), platinum (Pt), palladium (Pd) and rhodium (Rh), are critical for automotive emission control, chemical manufacturing and emerging energy technologies, yet their supply is limited and geographically concentrated. Their designation as critical raw materials (CRMs) in the EU has intensified recycling efforts, especially from spent automotive catalysts. Conventional pyrometallurgical and acid-based hydrometallurgical routes achieve high recovery efficiencies but rely on aggressive reagents and energy-intensive processing. Deep eutectic solvents (DESs) have emerged as greener leaching media capable of dissolving PGMs under milder and tunable conditions. This review outlines the conventional hydrometallurgical framework, summarizes DES fundamentals relevant to metals dissolution, and critically assesses recent advances in DES-based leaching of PGMs from spent catalysts. The influence of solvent composition, oxidants and complexing ligands on PGMs speciation and recovery is discussed, together with emerging reporting guidelines and research priorities. Overall, DES-based leaching offers a promising and potentially safer route for autocatalyst recycling but the technology remains at an early stage of development, requiring further mechanistic insight and sustainability evaluation. Full article

Nanoparticle powders of a Ce_1−xRu_xO₂ mixed oxide (3.0% w/w), were synthesized to be used as catalytic supports, on which Pt and Ir nanoparticles were deposited as the active phase. The catalytic supports were prepared through a route involving microwave heating, while the Pt or Ir nanoparticles were incorporated via the wet incipient method. The {Pt, Ir/Ce_1−xRu_xO₂} catalytic systems were successfully tested as catalysts for low-temperature CO oxidation. To provide adequate support to our results, the compounds were characterized by SEM, EDS, XRD, DRS-UV-vis, and XPS techniques. In addition, BET isotherms were carried out to determine specific surface area features. The CO oxidation evolution was tested in the range of 25–350 °C. Both Pt and Ir supported Ce_1−xRu_xO₂ catalysts that remarkably improved the CO oxidation, reaching and sustaining 100% conversion from 125 °C onwards. Remarkably, the mixed oxide support, by itself, showed outstanding performance, achieving 100% conversion to CO₂, at a temperature of 225 °C. Full article

The PGM-free Fe–Ni–Co trimetallic catalysts developed in this study demonstrated outstanding performance for the oxygen evolution reaction (OER), achieving overpotentials as low as 300 mV at 10 mA cm⁻² in rotating disk electrode (RDE) measurements, a value competitive with the most efficient non-noble electrocatalysts reported in the literature. This study validates the strong catalytic performance of the baseline trimetallic configuration and provides important insights into the relationships among synthesis, structure, and morphology that govern catalyst activity. In particular, the findings highlight that although organic additives can be promising modifiers, the interaction between precursors and transition metals must be carefully controlled to avoid active-site isolation when designing efficient catalysts for sustainable hydrogen production. Actually, to further enhance catalytic activity, the nitrogen-rich precursor melamine was introduced into the supported trimetallic catalyst and then carbonized. However, no improvement in OER performance was observed. During carbonization, melamine promotes the formation of tip-growth carbon nanotubes, which mechanically disrupt the catalyst structure and degrade the supported active phase. Full article

The reaction mechanism of the gold-catalyzed hydrothiolation of alkenes (1) with thiols (2) has been investigated in detail. The tetranuclear gold complex, (PPh₃)₄Au₄(SPh)₂(NTf)₂ (A), is a key intermediate in the catalytic hydrothiolation of alkenes. It forms instantaneously when PPh₃AuNTf₂ and PhSH are mixed in THF. Monitoring the reaction over time using ³¹P NMR spectroscopy revealed that gold complex A remained stable in the reaction system throughout the hydrothiolation process. In addition, we successfully observed a rapid ligand-exchange reaction between the thiolate group of gold complex A and thiols in solution. The gold-catalyzed alkene hydrothiolation reaction has been applied to the catalytic hydrothiolation of allenes, which have degenerate double bonds. Hydrothiolation of allenes proceeded regioselectively at the terminal double bond. However, the yield was lower than that observed for alkenes, and catalyst deactivation occurred. The hydrothiolation products of allenes were difficult to detach from the gold catalyst, necessitating an increase in the reaction temperature. Since high periodic transition metals such as gold and platinum are effective for hydrothiolation of alkenes and allenes, it is interesting to clarify whether iridium complexes, which belong to the same period as gold and platinum, could also catalyze alkene hydrothiolation. Through a detailed investigation of iridium ligands and reaction conditions, it was found that, in iridium systems, disulfide formation via oxidative coupling of thiols occurs preferentially over hydrothiolation reactions. This is likely due to steric hindrance around the iridium center, which inhibits alkene coordination to the iridium. Additionally, the hydrothiolation proceeding at low yields is believed to be a radical reaction involving electron transfer through the iridium complex. Full article

Catalytic materials are central to the advancement of hydrogen generation technologies, playing a pivotal role in enabling sustainable, carbon-neutral energy systems. Hydrogen can be produced via electrochemical water splitting, thermochemical reforming, or photocatalysis—each imposing unique performance requirements on catalysts in terms of activity, selectivity, stability, and efficiency. While traditional noble metals (e.g., platinum, ruthenium, iridium) provide benchmark catalytic activity, their widespread use is hindered by scarcity, high cost, and limited long-term durability. Consequently, researchers have increasingly focused on earth-abundant alternatives such as transition metals (Ni, Co, Fe, Mo), alloys, metal oxides, carbides, sulfides, nitrides, and carbon-based systems. Among these, two-dimensional materials, particularly the MXene family, have attracted significant attention due to their metallic conductivity, layered structure, and tunable surface chemistry. These features enable rapid charge transfer and abundant active sites, making MXenes and related nanostructured catalysts promising for both the Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) across a wide range of electrochemical conditions. Parallel efforts have integrated novel semiconductors, plasmonic nanomaterials, and hybrid heterostructures to improve the efficiency of solar-to-hydrogen energy conversion. This paper reviews the main types of catalytic materials used in hydrogen production, explains their design strategies and structure–performance relationships, and discusses key engineering challenges such as integrating renewable energy sources, scaling up manufacturing, and ensuring long-term durability in real-world systems. Future research goals are also highlighted, including the development of affordable non-noble catalysts, enhancing catalyst stability through surface and defect engineering, and coupling hydrogen production with circular economy principles, all of which are essential to making hydrogen generation more efficient, scalable, and cost-effective as the world transitions to clean and sustainable energy. Full article

Pt-based catalysts remain the most effective materials for the oxygen reduction reaction (ORR) at the cathode of proton exchange membrane fuel cells (PEMFCs); however, platinum scarcity and high cost severely limit the large-scale deployment of the technology. Improving catalytic activity and durability through precise control of nanoparticle morphology is therefore crucial for reducing costs and enhancing sustainability, enabling PEMFC widespread adoption. In this context, carbon-supported Pt-based nanoparticles with a 30 wt.% Pt loading were synthesized by an organometallic chemistry approach using hexadecylamine (HDA) as a stabilizer, allowing fine control over nanoparticle morphology. Two distinct synthesis pathways (one-pot and two-step procedures) were used to prepare platinum catalysts supported on KetjenBlack EC-300J (KB), and their influence on the electrocatalytic activity of the obtained nanomaterials was studied. Furthermore, the effect of HDA stabilization on catalyst performance was investigated. Directly synthesized Pt/KB catalysts exhibited similar ORR mass activity, regardless of whether or not HDA was present. Pt/KB prepared by the two-step procedure showed a significantly lower performance. Additionally, despite a larger loss of electrochemical surface area during an accelerated stress test compared to a commercial Pt/C reference, Pt^HDA/KB and Pt/KB catalysts maintained stable mass activity and limited specific activity degradation, highlighting the beneficial effect of nanoparticle stabilization in the presence of HDA on prolonged electrocatalyst cycling. Full article