Search Results (6,673)

Methanol is the simplest C1 oxygenated compound possessing the highest hydrogen-to-carbon ratio and can therefore be used as an effective hydrogen carrier. Furthermore, it can be easily transported by land and sea because it is liquid at room temperature and atmospheric pressure. Methanol can be converted into hydrogen via methanol steam reforming (MSR), aqueous-phase reforming of methanol (APRM), or aqueous methanol dehydrogenation (AMDH). In this review, various catalysts for MSR, APRM, and AMDH are summarized. Highly active and stable catalysts that can operate under low steam-to-methanol ratios are needed to increase the economics of the MSR process. Compared with the MSR process, the APRM process is rather simple because the water–gas shift reaction can occur simultaneously; however, more constraints exist in the selection of active metals and supports to ensure high activity and stability under APRM conditions. The inherently low reaction rate compared to MSR and the structural vulnerability of the catalyst under severe hydrothermal conditions are obstacles that the APRM catalysts must overcome. The low intrinsic catalytic activity and the high cost of homogeneous catalysts represent fundamental limitations inherent to AMDH catalysts. Based on a literature survey of MSR, APRM, and AMDH catalysts, some future research directions are also discussed. Full article

Thermochemical/catalytic co-processing of biomass and solid wastes is a promising route for waste valorization, low-carbon energy recovery, and the co-production of fuels, chemicals, and carbon materials. Conventional pathways, including pyrolysis, gasification, liquefaction, and carbonization, provide the basic framework for mixed-feed conversion. Emerging routes, such as flash Joule heating, microwave-assisted conversion, plasma processing, supercritical water treatment, solar-driven systems, and machine-learning-assisted optimization, further expand opportunities for process intensification and selective upgrading. Owing to feedstock complementarity, including hydrogen donation from plastics, catalytic effects of ash minerals, and interactions among reactive intermediates, co-processing can enhance deoxygenation, hydrogen generation, aromatization, and carbon utilization. Major challenges remain, however, including feedstock heterogeneity, reactor scale-up, catalyst stability, and the limited transferability of laboratory-scale synergy to realistic waste streams. Future progress should therefore focus on continuous validation, mechanistic clarification, and integrated techno-economic, life-cycle, and data-driven assessments. Full article

With changes in the global energy structure, ammonia has emerged as a favorable hydrogen storage medium due to its excellent properties. This work details the synthesis of a barium-doped cobalt–iron alloy catalyst via subsequent heat treatment. This alloy efficiently catalyzes the decomposition of ammonia into hydrogen. The results showed that using characterization methods such as TEM and XRD indicated that adding Ba to this system could regulate the microstructure of the Co-Fe alloy. After calcination, the barium promoted a reduction in the particle size of Co-Fe nanoparticles, enabling their uniform dispersion on the surface and a more uniform dispersion and improving the accessibility of the exposed surface. The optimized catalyst (0.05Ba-0.25CoFe/CeO₂) achieved an ammonia conversion of 93.2% at 550 °C under a gas hourly space velocity of 30,000 mL·g_cat⁻¹·h⁻¹. Mechanistic analysis based on XPS and CO₂-TPD results indicated that the barium optimized the electronic structure and alkaline sites of Co-Fe, promoted the desorption of nitrogen, and thereby accelerated the reaction kinetics of ammonia decomposition. This research provides a strategic method and theoretical basis for designing high-performance non-precious metal catalysts for ammonia decomposition. Full article

Biodiesel is a sustainable and promising alternative energy source produced from renewable raw materials using various methods. One effective approach is simultaneous esterification and transesterification, which relies on suitable catalysts that can be either homogeneous or heterogeneous. Homogeneous catalysts (acid or base) offer high activity but are corrosive and difficult to recover, necessitating energy-intensive processes such as aqueous quenching and neutralization, which can lead to soap formation and stable emulsions. By comparison, heterogeneous catalytic systems overcome many of these challenges due to their ease of recovery, reusability, and simplified product separation, which collectively enhance economic viability and environmental sustainability. This review highlights recent progress in the application of zeolite-based solid catalysts for biodiesel synthesis, with particular emphasis on their use in converting waste cooking oil and other low-cost feedstocks, including non-edible oils, non-food biomass sources, algal resources, and genetically engineered microorganisms. Key factors such as catalytic activity, selectivity, catalyst loading, and reusability are discussed, highlighting the advantages of zeolites due to their unique crystal structure, high thermal stability, and ease of product recovery. Overall, this review underscores the challenges and opportunities in zeolite-based catalysis to provide a comprehensive understanding of its potential to enhance the efficiency and scalability of biodiesel production. Full article

Ammonia is indispensable to the fertilizer and chemical industries, yet its manufacture still relies predominantly on the energy-intensive Haber–Bosch process operated at 400–500 °C and 150–250 bar, with a substantial carbon footprint. Single-atom catalysts (SACs) and sub-nanometric clusters have recently emerged as promising alternatives for thermocatalytic ammonia synthesis under milder conditions because they maximize metal utilization and enable precise control of the active site environment. This review first summarizes how the transition from conventional Fe and Ru nanoparticles to isolated or few-atom sites fundamentally alters the kinetic landscape, favoring associative N₂ activation pathways that lower apparent activation energies and alleviate H₂ poisoning. We then discuss Ru-based SACs and SAAs supported on zeolites, carbons, ceria, and MXenes, highlighting how strong metal–support and promoter interactions, tandem single-atom/nanoparticle motifs, and alloying strategies tune N₂ and H₂ binding to deliver high NH₃ productivities at 200–400 °C and ≤30 bar. In parallel, we review emerging non-noble systems based on Fe and Co, including high-loading Fe–N₄ sites prepared via MOF-derived post-metal-replacement routes and Co single atoms or Co₂ clusters on N-doped carbons, which already rival or surpass Ru benchmarks under similar conditions. Collectively, these studies show that tailoring the number of atom metal sites, coordination, and support polarity around isolated metal sites provides a useful tool to mitigate some aspects of volcano and scaling-relation limitations, indicating that SACs could contribute to low-temperature ammonia synthesis when combined with appropriate process design. Full article

Research on hydrogen production by chemical methods has focused on combining metals to carry out the hydrolysis reaction under ambient conditions. In particular, aluminum and lithium metals were considered, with lithium used at low concentrations in order to activate aluminum. Under these conditions, the metals can react with water to obtain the maximum hydrogen yield. The main objective of this work was to prepare the lithium−aluminum alloy by mechanical milling and its chemical reaction with water to produce hydrogen under laboratory conditions. A high–energy Spex mill was used for material preparation and the time scheduled for alloys preparation was relatively short. Several techniques were used for its characterization, such as X–ray diffraction, scanning electron microscopy, gas chromatography, and low-temperature physical adsorption. According to the results, two phases were produced during the milling process when using 5% lithium. The volume of hydrogen generated was measured using a graduated burette. Depending on the volume obtained, the aluminum reacted to generate hydrogen with an efficiency of 95.24%. No additives or catalysts were used in material synthesis or hydrogen production. According to these results, the hydrogen does not require any purification because it is clean hydrogen and can therefore be used directly in fuel cells. Full article

The Temporal Analysis of Products (TAP) pulse response technique provides valuable insights into catalytic function and reaction kinetics. However, complex fragmentation patterns in the TAP mass spectrometry signals can complicate precise quantification, particularly when analyzing transient gas flux data typical of TAP experiments. This work demonstrates a standard defragmentation method that deconvolves transient TAP signals while maintaining the temporal resolution of the experiment. First, the integrals of calibration gas fluxes are used to determine the fingerprint fragmentation pattern and construct a fragmentation matrix. This matrix is then used to defragment experimental flux data at each recorded time point via a non-negative least squares regression. The effectiveness of this method is demonstrated using virtual data and control experiments with a TAP reactor system. The defragmentation is then applied to the more complex propane dehydrogenation reaction on a chromia/alumina catalyst, which can contain up to ten significant gas species in the reactor outlet. Initial propane pulsing reveals an induction period during which propane is fully oxidized to CO_2, followed by partial reduction to CO. Afterwards, there is a transition in chemistries towards coking and propylene production. Our example illustrates a practical method for the accurate determination of the time-dependent reactant/product concentrations and rates for a thorough analysis of the propane dehydrogenation kinetics. This approach can be broadly applied to any transient mass spectrometry experiment for a better understanding of catalyst-reaction dynamics. Full article

Electrocatalytic H₂O₂ production via the two-electron oxygen reduction reaction (ORR) is a highly sustainable alternative to industrial methods. To further optimize non-noble catalysts, we report an interfacial engineering strategy to stabilize the metastable P6₃/mmc-La₂O₃ phase on SrTiO₃. This symmetry evolution from the low-symmetry $\mathrm{P}\stackrel{\mathrm{-}}{3}\mathrm{m}1$ (trigonal) to the high-symmetry P6₃/mmc (hexagonal) space group yields a composite with >95% H₂O₂ selectivity. Mechanistic studies demonstrate that the symmetry-regulated interface optimizes *OOH conversion and suppresses O–O bond cleavage. This work offers a robust design principle for high-performance, noble-metal-free H₂O₂ electrosynthesis. Full article

We report the synthesis of Fe/N/C ORR electrocatalysts by an original collinear CO₂ laser pyrolysis of liquid aerosol droplets in various configurations and compared them to a catalyst synthesized in the classical perpendicular one. While the precursors were always injected at the bottom side of the reactor, two collinear configurations of the laser entry into the reactor are considered: by the Top Side (T.S.) or by the Bottom Side (B.S.). The two corresponding catalysts sets show significant different ORR performances. An in-depth XPS analysis and fitting of the N1s spectra allowed for drawing the ORR performance as a function of FeN_x sites components. An original approach considering the energy delivered to a quantity of precursors in J.g⁻¹, linked to the flame temperature feature, evidenced very different conditions for perpendicular CO₂ laser pyrolysis and each of the two collinear configurations. This mass-weighted energy delivered in the classical perpendicular configuration is too low to allow for the formation of FeN_x sites and the resulting ORR performance is extremely poor, suggesting a marginal role of nitrogen species without interaction with iron atoms. In contrast, the delivered mass-weighted energies are sufficient in both collinear configurations to produce FeN_x sites. The ORR performance for catalysts produced in these both configurations is positively correlated with the amount of energy deposited on the precursors. The ORR performance in the T.S. laser configuration is positively correlated to the amount of FeN_x sites. The best performing catalysts obtained in the B.S. configuration show an opposite variation. These trends, and the ORR performance degradation of B.S. catalysts under prolonged chronoamperometry are discussed in light of the effect of temperature on the formation of the various kind of FeN_x sites. A tentative explanation is given, considering that N1s XPS fitting with a single FeN_x component may hinder the fact that Pyridinic sites components may contain a part of FeN_x sites, as suggested by theoretical calculation from the literature. The best catalysts obtained in this work by collinear configuration show similar performances to those obtained by double stage perpendicular pyrolysis previously reported with an ORR onset potential of ~860 mV. Full article

The efficiency of hydrogen production via water electrolysis is severely constrained by the sluggish reaction kinetics of the oxygen evolution reaction (OER). Herein, we constructed a nitrogen-doped CoFe Prussian blue analog (CoFePBA-N) electrocatalyst with a nanosheet-assembled cubic architecture by plasma. Plasma treatment induces morphological reconstruction and introduces nitrogen dopants and abundant vacancies, which not only increase the number of exposed active sites but also modulate the electronic structure of Co/Fe centers. Consequently, the optimized CoFePBA-N catalyst achieves a current density of 500 mA cm⁻² at low overpotentials of 322, 344, and 374 mV in alkaline freshwater, alkaline simulated seawater, and alkaline natural seawater, respectively. Furthermore, the catalyst maintains stable operation for over 300 h in alkaline freshwater and nearly 270 h in alkaline natural seawater, exhibiting exceptional durability. The enhanced catalytic performance is attributed to the synergistic effects of nitrogen doping, vacancies, and improved charge-transfer capability. This study provides an effective approach for modulating the electronic structure of Prussian blue analogs, thereby enabling efficient alkaline water and seawater electrolysis. Full article

Hydrogen peroxide (H₂O₂) plays a vital role as an eco-friendly oxidizer, extensively used in environmental cleanup, energy transformation, and organic production. Nonetheless, the conventional method of creating anthraquinones is intricate, resulting in significant energy and ecological costs, which calls for the development of more eco-friendly and efficient substitute technologies. The article methodically examines the reaction processes and methods for improving efficiency in photocatalytic H₂O₂ generation in the past few years. This review summarizes the design principles and key structural features of various novel catalytic materials, focusing on light absorption, charge separation and migration, surface redox reactions, and enhanced mass transfer. Approaches such as expanding the range of bandgap absorption, building conjugated structures, and incorporating metal nanoclusters can significantly enhance the efficiency of light absorption. In the charge separation process, constructing built-in electric fields at the interfaces of heterojunctions, homojunctions, and Schottky junctions is crucial for improving reaction efficiency. Additionally, defect engineering may encourage targeted carrier movement and minimize recombination. The review highlights the latest advancements in enhancing selectivity and reducing H₂O₂ breakdown in surface redox reactions, achieved by regulating active sites, introducing new functional groups, and developing dual-channel reaction pathways. Furthermore, constructing three-phase interfaces, regulating asymmetric wettability, and designing cyclic/flow reactors provide innovative engineering solutions to address the challenges of insufficient oxygen supply and large-scale continuous production. Ultimately, the potential for producing H₂O₂ in photocatalytic systems is detailed. Full article

This paper systematically reviews the recent advances in catalytic systems and reaction mechanisms for the synthesis of crotonaldehyde via aldol condensation using acetaldehyde as the feedstock. Firstly, the structural characteristics, reactivity, and important applications of crotonaldehyde in fine chemicals are outlined, with particular emphasis on the limitations of traditional homogeneous base-catalyzed processes, such as difficulty in separation and environmental pollution caused by waste streams. On this basis, heterogeneous catalytic systems are discussed in detail, focusing on the progress of metal oxides, aluminosilicate zeolites, and heteroatom zeolites in regulating acid–base properties, active site structures, and reaction pathways. Furthermore, the typical carbanion mechanism and direct condensation mechanism in aldol condensation are summarized, and the catalyst deactivation and by-product formation mechanisms are analyzed. Finally, perspectives on the construction of efficient and green catalytic systems and future research directions are proposed, aiming to provide theoretical guidance for process optimization and catalyst design in crotonaldehyde synthesis from acetaldehyde. Full article

Additive manufacturing (AM) is a process that creates a three-dimensional (3D) physical object from a digital design by building layers of material directly from a computer-aided design (CAD) file, allowing for precise and rapid production of parts or prototypes. AM is increasingly recognised as a sustainable production method due to its potential to reduce waste, energy consumption, and environmental impact. The versatility and efficiency of AM have made it an essential tool for rapid prototyping and developing custom parts and components with intricate designs that were previously difficult or impossible to produce. This review highlights the significant progress in utilising AM for the synthesis of organic compounds and the fabrication of organic devices. AM technologies are used in the synthesis of organic compounds, particularly through the use of 3D-printed catalysts, reactors and flow systems. Advances in AM have enabled this technology to be used to synthesise organic compounds and produce low-cost, customised organic equipment. This makes it possible to obtain sophisticated reactors, laboratory equipment or their individual parts, tailored to a specific chemical process in more sustainable way. AM has great potential for advancing green and sustainable chemical processes, with the ability to integrate multiple enabling technologies and facilitate safer and more efficient processes in a cost-effective manner. Overall, the integration of AM in organic synthesis has opened up new possibilities for innovative solutions in the field. Full article

ALD is a precise thin-film deposition technique based on self-limiting surface reactions. A crucial stage in each ALD cycle is the purge step, which removes excess precursor molecules and reaction by-products from the reactor chamber, preventing uncontrolled gas-phase reactions that could degrade film quality. Despite its fundamental importance, the impact of purge dynamics on film growth and structure remains insufficiently explored. ZnO and ZrO₂ films were deposited in reactors with different effective chamber volumes (47 and 470 cm³), enabling a systematic study of gas residence time effects. Our results demonstrate that the purge mode—dynamic versus static vacuum—strongly affects the growth behavior, crystallinity, and surface morphology of ALD oxides. Dynamic purging leads to smoother, more uniform, and better-crystallized films, whereas static exposure results in lower structural and morphological quality, particularly for ZrO₂. Importantly, these results demonstrate that purge-mode engineering provides a powerful and cost-effective route for tailoring oxide film structure without altering the precursor chemistry or deposition temperature. To validate the practical integration of these optimized films, functional phosphor and LED structures were fabricated, confirming that the controlled microstructure is well-suited for optoelectronic applications. This approach also offers new possibilities for controlling film properties in sensors and catalysts. Full article

As solid waste generated from shield tunnel construction, shield muck is characterized by its massive volume, high water content, and poor engineering properties. Large-scale stockpiling not only occupies precious land resources but also poses potential environmental risks. This has become one of the key bottlenecks hindering the green, low-carbon, and sustainable development of rail transit construction. Efficient dewatering is a key prerequisite for its subsequent disposal or reutilization. Lime, cement, phosphogypsum, nano-SiO₂, and ground granulated blast furnace slag were employed in this research as composite conditioning agents to dewater shield tunnel muck. A range of water content, pH, and total organic carbon analyses tests were conducted to explore the roles of lime, cement, phosphogypsum, nano-SiO₂, and ground granulated blast furnace slag on the dewatering effect of shield tunnel muck. Furthermore, microstructures and elemental distribution of typical mixes were analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy tests. Results indicate that a composite agent consisting of 3.5% lime, 4% cement, 1% phosphogypsum, 0.2% nano-SiO₂, and 4% ground granulated blast furnace slag exhibits optimal performance, reducing water content from 50% to 29.8% within 24 h. Phosphogypsum significantly decreased pH and reduced TOC to below 1 g/kg after 15 days, effectively mitigating the environmental hazards associated with muck disposal. The formation of cementitious products, including calcium aluminate hydrate, calcium aluminosilicate hydrate gels, and calcium silicate hydrate, effectively bonds soil particles. Additionally, ettringite crystals produced by the reaction between phosphogypsum and calcium aluminate phases filled interparticle voids. These processes were identified as the primary mechanisms for water reduction. Although nano-SiO₂ exerted a limited direct influence on water content, it acted as a pozzolanic catalyst that accelerated hydration reactions of lime and cement, rapidly reducing muck fluidity. The synergistic effect of the composite dewatering agent components establishes a multi-mechanism dewatering system characterized by “hydration gel + AFt filling + nano-catalysis.” The dewatering system developed in this study achieves both high efficiency and environmental friendliness for shield tunnel muck. This provides technical support for subsequent resource utilization, such as subgrade filling, while promoting the recycling of industrial solid wastes like phosphogypsum and blast furnace slag, ultimately contributing to green, low-carbon, and sustainable development. Full article