15th Anniversary of Catalysts: Catalytic Materials and Processes for H2 and E-Fuel Production from Wastes

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Catalytic Materials".

Deadline for manuscript submissions: 30 October 2026 | Viewed by 6186

Special Issue Editors


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Institute of Nanostructured Materials, Palermo Research Division, CNR-ISMN, Via Ugo La Malfa 153, 90146 Palermo, Italy
Interests: supported noble metals; nanostructured and mesoporous oxides; inorganic perovskites; catalytic applications in soot oxidation and NOx SCR of exhaust gases emitted from stationary and mobile sources; VOC oxidation; dry/steam hydrocarbon reforming; CO2 hydrogenation to CH4 and light olefines
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School of Chemical Engineering, Zhengzhou University, Zhengzhou 450001, China
Interests: design of nano metal catalysts; heterogeneous catalytic selective oxidation; green synthesis of biomass-based fine chemicals from glycerol
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Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macau 999078, China
Interests: electrocatalysis; hybrid sodium–air batteries; supercapacitors; zinc–air batteries; water-splitting; graphene; transition metal oxide; phosphorus synthesis
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Faculty of Physics, Institute for Research-Development-Innovation in Applied Natural Sciences, Institute of Interdisciplinary Research in Bio-Nano-Sciences, Babes-Bolyai University, Cluj-Napoca, Romania
Interests: biomaterials; photocatalysts and graphene-based materials
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Special Issue Information

Dear Colleagues,

The year 2026 marks the 15th anniversary of MDPI’s Catalysts, a monthly, peer‑reviewed open access journal on catalysts and catalyzed reactions that was established in 2011.

We welcome experts in catalysis, materials science, energy conversion, and environmental engineering to contribute to this Special Issue, which aims to highlight innovations in sustainable hydrogen and e-fuel production from waste-derived resources. Suggested thematic areas and directions for contribution are listed below.

  1. Catalytic Material Design and Innovation
  • The design of nanostructured, bimetallic, or support-enhanced catalysts for H₂ generation.
  • Electrocatalysts or photocatalysts for water-splitting or CO2 valorization.
  • Catalyst stability, deactivation mechanisms, and regeneration strategies.
  • Theoretical and computational approaches (e.g., DFT, machine learning) to guide the development of catalysts.
  1. Thermochemical and Catalytic Waste Conversion

Suggested contributors: Specialists in biomass, plastic, and waste valorization.

Topics may include the following:

  • The steam reforming, dry reforming, or gasification of organic waste.
  • Catalytic pyrolysis or hydrothermal liquefaction/gasification.
  • The integration of catalytic processes with waste pretreatment methods.
  • Hybrid systems such as plasma-assisted or microwave-assisted catalysis.
  1. Catalysis in Power-to-X Systems and E-Fuel Synthesis
  • The catalytic hydrogenation of CO2 to fuels (methane, methanol, or hydrocarbons).
  • Fischer–Tropsch synthesis and synthetic fuel pathways using renewable H2.
  • The coupling of waste-derived syngas with H2 from electrolysis.
  • Modular Power-to-X systems and their catalytic challenges.
  1. Circular Economy, Policy, and Sustainability Analysis
  • Circular strategies for waste-derived fuels.
  • Life-cycle analysis (LCA) and carbon footprint evaluation.
  • The integration of waste-to-fuel systems in decentralized or off-grid contexts.
  • Regulatory frameworks, market trends, and sustainability criteria for H2 and e-fuels.

If you would like to submit papers to this Special Issue or have any questions, please contact the in-house editor, Ms. Rita Lin (rita.lin@mdpi.com).

Dr. Leonarda Liotta
Prof. Dr. Tianliang Lu
Dr. Kwun Nam Hui
Prof. Dr. Lucian Baia
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • hydrogen production
  • CO2 utilization
  • waste valorization
  • electrochemical conversion
  • sustainability assessment
  • renewable fuels: (photo)catalytic materials

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Published Papers (8 papers)

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Research

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24 pages, 2781 KB  
Article
Temperature-Dependent Ethylene Aromatization over Metal-Modified HZSM-5: Thermodynamics and Kinetics Analysis
by Pengcheng Feng, Yue He, Sen Wang, Zhiwei Wu, Tianfu Zhang, Weibin Fan and Mei Dong
Catalysts 2026, 16(5), 437; https://doi.org/10.3390/catal16050437 - 8 May 2026
Viewed by 228
Abstract
The ethylene aromatization (ETA) reaction is a pivotal route for non-petroleum-based aromatics production, yet a systematic understanding of its thermodynamic constraints and kinetic modulation remains elusive. Herein, an integrated thermodynamic and kinetic study is presented to elucidate the temperature-dependent reaction pathways over metal [...] Read more.
The ethylene aromatization (ETA) reaction is a pivotal route for non-petroleum-based aromatics production, yet a systematic understanding of its thermodynamic constraints and kinetic modulation remains elusive. Herein, an integrated thermodynamic and kinetic study is presented to elucidate the temperature-dependent reaction pathways over metal oxide-modified HZSM-5 catalysts. Thermodynamic calculations reveal that while oligomerization, cyclization, and the hydrogen transfer (HT) pathway are exothermic, the aromatics-generating dehydrogenation (DH) pathway is endothermic. Crucially, despite the general thermodynamic penalty imposed by elevated temperatures on most elementary steps, the overall ethylene aromatization reaction retains a strong driving force, underscoring the dehydrogenation pathway as the thermodynamic and kinetic key to aromatic selectivity. Experimentally, it is demonstrated that modifying HZSM-5 with ZnO, Ga2O3, and ZnGa2O4 effectively tunes the Lewis-to-Brønsted acid (L/B) ratio. A strong linear correlation is established between the L/B ratio and the apparent activation energy, with a higher L/B ratio significantly lowering the activation barrier. This synergistic effect optimally promotes the dehydrogenation pathway, suppresses alkane by-product formation, and maximizes aromatic yield within an optimal temperature window of 470–520 °C. The findings provide a fundamental and practical framework for the rational design of high-efficiency ethylene aromatization catalysts and the optimization of process conditions via targeted acid site engineering. Full article
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28 pages, 8562 KB  
Article
Structure–Acidity–Activity Correlation in Ammonia Decomposition over Al-Based Mixed-Oxide Catalysts: A Combined Surface and Kinetic Study
by Mihaela Litinschi (Bilegan), Rami Doukeh, Romuald Győrgy, Ionuț Banu, Alexandru Vlaicu, Gabriel Vasilievici, Sorin Georgian Moga, Andreea Madalina Pandele and Dragos Mihael Ciuparu
Catalysts 2026, 16(5), 405; https://doi.org/10.3390/catal16050405 - 1 May 2026
Viewed by 271
Abstract
Ammonia decomposition represents a promising route for CO2-free hydrogen production; however, the development of efficient and stable catalysts remains a critical challenge. In this work, a series of Al-based mixed-oxide catalysts (AlM, where M = Ni, Co, Ce) were synthesized via [...] Read more.
Ammonia decomposition represents a promising route for CO2-free hydrogen production; however, the development of efficient and stable catalysts remains a critical challenge. In this work, a series of Al-based mixed-oxide catalysts (AlM, where M = Ni, Co, Ce) were synthesized via co-precipitation and systematically investigated to elucidate the relationship between physicochemical properties and catalytic performance in ammonia decomposition. Comprehensive characterization by X-ray diffraction (XRD), N2 physisorption (BET), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and pyridine-adsorbed Fourier transform infrared spectroscopy (FTIR-Py) revealed significant variations in surface area, morphology, dispersion, and acidity as a function of the incorporated metal. Among the investigated catalysts, the AlNi system exhibited superior activity, achieving the highest ammonia conversion over the studied temperature range. This enhanced performance is attributed to its high specific surface area, homogeneous mesoporous structure, and a balanced distribution of Lewis/Brønsted acid sites, which promote effective ammonia adsorption, activation and decomposition. Kinetic analysis further confirmed the favorable reaction pathway on AlNi, as evidenced by its lower apparent activation energy and higher pre-exponential factor compared to the other materials. The results demonstrate a clear correlation between surface acidity, textural properties, and catalytic performance, highlighting the pivotal role of AlM interactions in governing ammonia decomposition. These findings provide valuable insights for the rational design of efficient catalysts for hydrogen production from ammonia. Full article
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15 pages, 2122 KB  
Article
Ammonia Cracking over Sn-Co Molten Alloys in a Bubble Column Reactor
by Jonghwi Park, Sungwan Kwon, Jihun Kim, Ryun Na Kim, Jongkyu Kang, Young Jae Lee, Dahin Kim, Uendo Lee and Whi Dong Kim
Catalysts 2026, 16(3), 277; https://doi.org/10.3390/catal16030277 - 20 Mar 2026
Cited by 1 | Viewed by 811
Abstract
Ammonia has emerged as a strategically advantageous hydrogen carrier; however, its efficient decomposition using conventional solid catalysts remains technically challenging from an industrial standpoint, particularly in terms of long-term stability and large-scale implementation. In this study, we propose a strategy for ammonia cracking [...] Read more.
Ammonia has emerged as a strategically advantageous hydrogen carrier; however, its efficient decomposition using conventional solid catalysts remains technically challenging from an industrial standpoint, particularly in terms of long-term stability and large-scale implementation. In this study, we propose a strategy for ammonia cracking by utilizing Sn-based molten metal alloys in a bubble column reactor, which provides a sintering-resistant and thermally efficient catalytic platform. Among various candidate transition metals, the Sn-Co alloy exhibited the most superior catalytic performance, demonstrating a significant reduction in the apparent activation energy to 52.6 kJ/mol. To the best of our knowledge, this study provides the first experimental evidence of the catalytic role of molten metals in the ammonia decomposition process. Structural characterization confirmed that the molten alloy maintains its metallic state without the formation of nitrides, verifying the function of the molten metal as an active catalyst rather than a sacrificial reagent. This work offers a new catalytic approach that addresses the requirements for the commercialization of ammonia cracking through improved scalability and chemical durability. Full article
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15 pages, 4914 KB  
Article
Nickel Catalysts Supported on SiO2-CeO2 Mixed Oxides for Methane Dry Reforming
by Carla Calabrese, Valeria La Parola, Giuseppe Pantaleo and Leonarda Francesca Liotta
Catalysts 2026, 16(3), 231; https://doi.org/10.3390/catal16030231 - 3 Mar 2026
Viewed by 696
Abstract
Nickel-supported catalysts over SiO2-CeO2 mixed oxides were investigated as catalysts for syngas production via dry reforming of methane. SiO2-CeO2 supports were optimized by varying the preparation method and ceria loading with the aim of stabilizing nickel nanoparticles, [...] Read more.
Nickel-supported catalysts over SiO2-CeO2 mixed oxides were investigated as catalysts for syngas production via dry reforming of methane. SiO2-CeO2 supports were optimized by varying the preparation method and ceria loading with the aim of stabilizing nickel nanoparticles, enhancing the catalytic performance, and improving the resistance to coke formation under high-temperature reforming conditions. To investigate the effect of support composition, SiO2-CeO2 mixed oxides with ceria contents ranging from 5 to 30 wt% were prepared using two synthesis routes: sol–gel and wetness impregnation methods. A nickel loading of 5 wt% was deposited on the resulting supports. The catalysts were characterized by XRD, N2 physisorption, temperature-programmed reduction (TPR), and Raman spectroscopy. Catalytic activity tests were carried out over reduced catalysts in an H2-He stream at 750 °C, using a feed mixture containing 15 vol% CH4 and 15 vol% CO2 in He. The effect of temperature on catalytic performance was evaluated in the range of 450–750 °C. Thermogravimetric, XRD and Raman analyses of spent catalysts were used to assess carbon deposition and the nature of crystalline phases. The results highlight the role of CeO2 content and preparation method in determining nickel dispersion, reducibility, catalytic performance in DRM, and coke resistance. Full article
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18 pages, 3332 KB  
Article
Effect of Mn/Cu Ratio on the Structure–Performance Relationship of Spinel-Type Mn–Cu/Al2Ox Catalysts for Methanol Steam Reforming
by Qiang Zhang, Shiming Qiu, Yanfei Zheng and Yingying Huang
Catalysts 2025, 15(11), 1091; https://doi.org/10.3390/catal15111091 - 20 Nov 2025
Cited by 1 | Viewed by 1074
Abstract
The development of highly active, thermally stable, and low-CO-selective catalysts is critical for practical methanol steam reforming (MSR) to produce high-purity hydrogen for fuel cell applications. In this work, a series of Mn–Cu/Al2Ox catalysts with varying Mn/Cu/Al molar ratios were [...] Read more.
The development of highly active, thermally stable, and low-CO-selective catalysts is critical for practical methanol steam reforming (MSR) to produce high-purity hydrogen for fuel cell applications. In this work, a series of Mn–Cu/Al2Ox catalysts with varying Mn/Cu/Al molar ratios were synthesized via co-precipitation and systematically investigated to establish the relationship between composition, structure, and catalytic performance. XRD analysis revealed the formation of spinel-type CuAl2O4 and MnAl2O4 phases, with Mn preferentially occupying octahedral B-sites to form MnAl2O4, thereby inducing lattice distortion and inhibiting grain growth. SEM and TEM–EDS mapping confirmed uniform elemental distribution and a porous nanoscale morphology, while H2-TPR results suggested that increasing the Mn/Cu ratio strengthens Mn–Cu interactions, shifts Cu2+ reduction to higher temperatures, and enhances Cu dispersion (up to 26.11 m2/g). XPS analysis indicated that Mn doping enriches Mn3+ species and facilitates oxygen vacancy formation, which promotes water–gas shift (WGS) activity and suppresses CO formation. Catalytic testing (240–300 °C) showed that Mn2Cu2Al4Ox achieved the highest methanol conversion while maintaining low CO selectivity; in contrast, reducing the Mn/Cu ratio increased CO selectivity, detrimental to hydrogen purification. Stability tests under continuous steam exposure for 24 h demonstrated minimal activity loss (~2%) and negligible increase in CO selectivity (<1%), confirming excellent hydrothermal stability. The results indicate that tailoring the Mn/Cu ratio optimizes the balance between redox properties and metallic Cu dispersion, offering a promising route to design low-CO, durable catalysts for on-site hydrogen generation via MSR. Full article
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13 pages, 2076 KB  
Article
Study on the Effect of Precious Metal Loading and Pt/Pd Ratio on Gaseous Pollutant Emissions from Diesel Engines
by Kun Shao, Heng Wu and Yantao Zou
Catalysts 2025, 15(10), 974; https://doi.org/10.3390/catal15100974 - 12 Oct 2025
Viewed by 1089
Abstract
This study systematically investigated the influence of catalyst formulation parameters (precious metal loading and Pt/Pd ratio) in diesel oxidation catalysts (DOCs)+catalyzed diesel particulate filter (CDPF)+selective catalytic reduction (SCR) on gaseous pollutant emissions from diesel engines. Results indicate that under varying conditions, the impact [...] Read more.
This study systematically investigated the influence of catalyst formulation parameters (precious metal loading and Pt/Pd ratio) in diesel oxidation catalysts (DOCs)+catalyzed diesel particulate filter (CDPF)+selective catalytic reduction (SCR) on gaseous pollutant emissions from diesel engines. Results indicate that under varying conditions, the impact of catalyst formulation on DOC system performance—such as temperature rise characteristics, pressure drop, and brake specific fuel consumption (BSFC)—remains limited. Notably, exhaust temperature exerts a decisive influence on carbon monoxide (CO) and hydrocarbon (HC) conversion efficiency, significantly outweighing the impact of exhaust flow rate. Increasing precious metal loading and Pt proportion markedly optimizes CO and HC ignition characteristics by lowering ignition temperatures. However, under high-load conditions, conversion efficiencies across different catalyst formulations tend to converge. Specifically, under low-load conditions, a competitive adsorption mechanism between CO and HC causes HC conversion efficiency to exhibit an inverse trend relative to CO. Furthermore, higher precious metal loading and Pt content significantly enhance the catalyst’s NO2 formation capacity at equilibrium temperatures, while higher Pd content contributes to improved thermal stability. Higher precious metal loading and Pt content increase nitrogen oxides (NOx) conversion efficiency. CDPF possesses the ability to further oxidize NO. Full article
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14 pages, 1821 KB  
Article
Hydrothermal Aging Mechanism of CeO2-Based Catalytic Materials and Its Structure–Activity Relationship Study on Particulate Matter Oxidation Performance
by Yantao Zou and Liguang Xiao
Catalysts 2025, 15(10), 962; https://doi.org/10.3390/catal15100962 - 7 Oct 2025
Cited by 1 | Viewed by 1077
Abstract
With the increasing emphasis on environmental protection and sustainable development, improving air pollution control technology has become imperative. In this study, Ce-based catalysts are used as research objects to explore the effects of hydrothermal aging on their performance in oxidizing PM. Different Mn, [...] Read more.
With the increasing emphasis on environmental protection and sustainable development, improving air pollution control technology has become imperative. In this study, Ce-based catalysts are used as research objects to explore the effects of hydrothermal aging on their performance in oxidizing PM. Different Mn, Na, Pt and Zr-doped Ce-based catalysts were prepared based on the impregnation method and the PM oxidation performance of Ce-based catalysts before and after hydrothermal aging was investigated using thermogravimetric experiments, and the catalytic activity change pattern of fresh/hydrothermal aging Ce-based catalysts was analyzed by comparing the comprehensive combustion index S and combustion stability index Rw, revealing the PM oxidation process. The conclusion showed that the cerium-based catalyst significantly enhanced the oxidation efficiency of PM compared with PU. By comparing the performance of different metal-modified catalysts, it was found that the order of activity was: Pt > Na > Mn > Zr. With the metal doping increased, only the comprehensive combustion index S and combustion stability index Rw of Na/CeO2 catalysts decreased. After hydrothermal aging treatment, the Zr/CeO2 catalysts showed the best hydrothermal aging resistance, and the comprehensive combustion index S and combustion stability index Rw remained stable (<5%). Ce-based catalysts have the strongest to weakest hydrothermal aging resistance in the following order: Zr > Mn > Pt > Na. This study not only provides an important scientific reference for the application of Ce-based catalysts in the field of environmental purification but also contributes new ideas and methods to promote the green and sustainable development of air pollution control technology. Full article
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Review

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38 pages, 2992 KB  
Review
Surface Intermediates in Important Catalytic Reactions: Formation, Identification and Reactivity Across Metals, Nanoparticles and Supported Catalysts
by János Kiss, Imre Szenti, Anastasiia Efremova, Imre Kovács, Aranka Deér, András Sápi and Zoltán Kónya
Catalysts 2026, 16(5), 404; https://doi.org/10.3390/catal16050404 - 1 May 2026
Viewed by 293
Abstract
The performance and mechanism of heterogeneous catalytic reactions are fundamentally governed by the formation, stability, and reactivity of transient surface intermediates. These species—such as isocyanates, alkyl groups, carboxylates, formates, carbonates, alkoxy and acyl intermediates—often exist at low concentrations and with short lifetimes, making [...] Read more.
The performance and mechanism of heterogeneous catalytic reactions are fundamentally governed by the formation, stability, and reactivity of transient surface intermediates. These species—such as isocyanates, alkyl groups, carboxylates, formates, carbonates, alkoxy and acyl intermediates—often exist at low concentrations and with short lifetimes, making their identification challenging. This review summarizes the current knowledge on the formation, spectroscopic identification, and thermal behavior of these intermediates on metal single crystals, metal nanoparticles, and oxide-supported catalysts. Emphasis is placed on key reactions including CO and NO oxidation–reduction, CO and CO2 hydrogenation, Fischer–Tropsch-related pathways, and reforming of ethanol. Advanced surface-sensitive techniques (TDS, XPS, UPS, IR, HREELS) are highlighted for their role in elucidating intermediate structures and reaction pathways. The isocyanate surface complex is an existing intermediate in NO reduction with CO, and NCO is responsible for NH3 formation. Alkyl groups can be prepared from thermal- or photo-induced dissociation of alkyl halogenide. Oxygen-containing intermediates relevant to CO2 hydrogenation are addressed, with particular attention to formate, carboxylate, and related species. M/CeO2 (M = Pt, Rh, Ir, Ru) seems to be the best catalyst for hydrogen production from ethanol reforming. The nature of support may affect hydrogen production. The review also discusses how metal–support interactions, particle size, and surface morphology influence intermediate stability and catalytic selectivity. Overall, the work provides a comprehensive framework for understanding how transient surface complexes control technologically important catalytic transformations. Full article
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