Search Results (133)

This review analyzes the catalytic routes for the Power-to-X (PtX) conversion of hydrogen to methane, methanol, ammonia, formic acid, and synthetic hydrocarbon fuels. The key reactive synthesis technologies and catalysts for each vector are described. Recent studies and pilot projects summarizing the reaction pathways of each vector and the associated catalyst technologies are also discussed. The analysis indicates that catalyst selection critically influences the efficiency and selectivity of these reactive systems. Some catalyst synthesis routes rely on expensive critical minerals (e.g., Ru and Rh), which raise technical and economic challenges for their industrial application. Catalyst deactivation and scale-up limitations are also relevant issues to be resolved. Emerging catalysts (e.g., Fe–Co or Co–Ni bimetallics, core–shell materials, metal-organic frameworks (MOFs), electrides, covalent-organic frameworks (COFs), and perovskites) are being explored to enhance stability, selectivity, and deactivation. Europe leads PtX development to consolidate the industrial production of hydrogen-based vectors with strong policy support, while the industrial initiatives in Latin America are limited (for instance, Chile’s green methanol and ammonia projects are examples) despite its great potential to generate renewable energy. In summary, Power-to-X can store renewable energy and close the carbon loop; however, its industrial consolidation demands catalyst innovation and supportive regulatory frameworks to overcome the challenges highlighted in this review. Full article

The biogas dry reforming reaction offers a promising route for syngas production while simultaneously mitigating greenhouse gas emissions. Membrane reactors have proven to be an excellent option for hydrogen production and separation in a single unit, where conversion and yield can be enhanced over conventional processes. In this study, a Pd/YSZ membrane integrated with a Ru/CeO₂ catalyst was evaluated for biogas reaction under varying operating conditions. The selective removal of hydrogen through the palladium membrane improved reactant conversion and suppressed side reactions such as methanation and the reverse water–gas shift. Experiments were performed at temperatures ranging from 500 to 600 °C, pressures of 1–6 bar, and a gas hourly space velocity (GHSV) of 800 h⁻¹. Maximum conversions of CH₄ (43%) and CO₂ (46.7%) were achieved at 600 °C and 2 bar, while the maximum hydrogen recovery of 78% was reached at 6 bar. The membrane reactor outperformed a conventional reactor, offering up to 10% higher CH₄ conversion and improved hydrogen production and yield. Also, a comparative analysis between Ru/CeO₂ and Ni/Al₂O₃ catalysts revealed that while the Ni-based catalyst provided higher CH₄ conversion, it also promoted methane decomposition reaction and coke formation. In contrast, the Ru/CeO₂ catalyst exhibited excellent resistance to coke formation, attributable to ceria’s redox properties and oxygen storage capacity. The combined system of Ru/CeO₂ catalyst and Pd/YSZ membrane offers an effective and sustainable approach for hydrogen-rich syngas production from biogas, with improved performance and long-term stability. Full article

Electrocatalytic water splitting offers a promising route to sustainable H₂, but the oxygen evolution reaction (OER) in alkaline media remains the principal bottleneck for activity and durability. This review focuses on alkaline OER and integrates mechanism, kinetics, materials design, and cell-level considerations. Reaction mechanisms are outlined, including the adsorbate evolution mechanism (AEM) and the lattice oxygen mediated mechanism (LOM), together with universal scaling constraints and operando reconstruction of precatalysts into active oxyhydroxides. Strategies for electronic tuning, defect creation, and heterointerface design are linked to measurable kinetics, including iR-corrected overpotential, Tafel slope, charge transfer resistance, and electrochemically active surface area (ECSA). Representative catalyst families are critically evaluated, covering Ir and Ru oxides, Ni-, Fe-, and Co-based compounds, carbon-based materials, and heterostructure systems. Electrolyte engineering is discussed, including control of Fe impurities and cation and anion effects, and gas management at current densities of 100–500 mA·cm⁻² and higher. Finally, we outline challenges and directions that include operando discrimination between mechanisms and possible crossover between AEM and LOM, strategies to relax scaling relations using dual sites and interfacial water control, and constant potential modeling with explicit solvation and electric fields to enable efficient, scalable alkaline electrolyzers. Full article

In recent years CO₂ reforming of methane has attracted great interest as it produces high CO/H₂ ratio syngas suitable for the synthesis of higher hydrocarbons and oxygenated derivatives since it is a way for disposing and recycling two greenhouse gases with high environmental impact, CH₄ and CO₂, and because it is regarded as a potential route to store and transmit energy due to its strong endothermic effect. Along with noble metals, all the group VIII metals except for osmium have been studied for catalytic CO₂ reforming of methane. It was found that the catalytic activity of Ni, though lower than those of Ru and Rh, was higher than the catalytic activities of Pt and Pd. Although noble metals have been proven to be insensitive to coke, the high cost and restricted availability limit their use in this process. It is therefore valuable to develop stable Ni-based catalysts. In this contribution, we show how their activity and coking resistivity are greatly related to the size and dispersion of Ni particles. Well-dispersed Ni nanoparticles were achieved by multistep impregnation on a mesoporous silica support, namely SBA-15, obtained through a sol-gel method, using acetate as a nickel precursor and keeping the Ni loading between 5% and 11%. Significant catalytic activity was obtained at temperatures as low as 450 °C, a temperature well below their deactivation temperature, i.e., 700 °C. For the pre-reduced samples, a CO₂ conversion higher than 99% was obtained at approximately 680 °C. As such, their deactivation by sintering and coke formation was prevented. To the best of our knowledge, no Ni-based catalysts with complete CO₂ conversion at temperatures lower than 800 °C have been reported so far. Full article

This research presents the development of spinel-type high-entropy oxide (HEO) catalysts with the general composition (MnFeNiCoX)₃O₄, where X represents Cr, Cu, Zn, and Cd, synthesized through a solution combustion method. The impact of the fifth metal element on the oxygen evolution reaction (OER) was systematically explored using structural, morphological, and electrochemical characterization techniques. Among the various compositions, the Cr-containing catalyst, (MnFeNiCoCr)₃O₄, displayed outstanding electrocatalytic behavior, delivering a notably low overpotential of 323 mV at a current density of 10 mA/cm² in 1.0 M KOH—surpassing the performance of benchmark RuO₂. Additionally, this material exhibited the smallest Tafel slope (56 mV/dec), the greatest double-layer capacitance (3.35 mF/cm²), and the most extensive electrochemically active surface area, all indicating enhanced charge transfer capability and high catalytic proficiency. The findings highlight the potential of element tailoring in HEOs as a promising strategy for optimizing water oxidation catalysis. Full article

Industrial catalysts are accelerating the global transition toward renewable energy, serving as enablers for innovative technologies that enhance efficiency, lower costs, and improve environmental sustainability. This review explores the pivotal roles of industrial catalysts in hydrogen production, biofuel generation, and biomass conversion, highlighting their transformative impact on renewable energy systems. Precious-metal-based electrocatalysts such as ruthenium (Ru), iridium (Ir), and platinum (Pt) demonstrate high efficiency but face challenges due to their cost and stability. Alternatives like nickel-cobalt oxide (NiCo₂O₄) and Ti₃C₂ MXene materials show promise in addressing these limitations, enabling cost-effective and scalable hydrogen production. Additionally, nickel-based catalysts supported on alumina optimize SMR, reducing coke formation and improving efficiency. In biofuel production, heterogeneous catalysts play a crucial role in converting biomass into valuable fuels. Co-based bimetallic catalysts enhance hydrodeoxygenation (HDO) processes, improving the yield of biofuels like dimethylfuran (DMF) and γ-valerolactone (GVL). Innovative materials such as biochar, red mud, and metal–organic frameworks (MOFs) facilitate sustainable waste-to-fuel conversion and biodiesel production, offering environmental and economic benefits. Power-to-X technologies, which convert renewable electricity into chemical energy carriers like hydrogen and synthetic fuels, rely on advanced catalysts to improve reaction rates, selectivity, and energy efficiency. Innovations in non-precious metal catalysts, nanostructured materials, and defect-engineered catalysts provide solutions for sustainable energy systems. These advancements promise to enhance efficiency, reduce environmental footprints, and ensure the viability of renewable energy technologies. Full article

Single-atom catalysts (SACs) have emerged as highly promising catalytic materials for the hydrogen evolution reaction (HER), attributed to their maximal atomic utilization efficiency and unique electronic configurations. Many structure parameters can influence the catalytic performance of SACs for HER, and the intrinsic advantages of SACs for HER still need to be summarized. This review systematically summarizes recent advances in SACs for HER. It discusses various types of SACs (including those based on Pt, Co, Ru, Ni, Cu, and other metals) applied in HER, and elaborates the critical factors influencing catalytic performance—specifically, the supports, coordination environments, and synergistic effects of these SACs. Furthermore, current research challenges and future perspectives in this rapidly developing field are also outlined. Full article

This review explores CO₂ methanation and steam methane reforming (SMR) as two key thermochemical processes governed by reversible reactions, each offering distinct contributions to carbon-neutral energy systems. The objective is to provide a comparative assessment of both processes, highlighting how reaction reversibility can be strategically leveraged for decarbonization. The study addresses methane production via CO₂ methanation and hydrogen production via SMR, focusing on their thermodynamic behaviors, catalytic systems, environmental impacts, and economic viability. CO₂ methanation, when powered by renewable hydrogen, can result in emissions ranging from −471 to 1076 kg CO₂-equivalent per MWh of methane produced, while hydrogen produced from SMR ranges from 90.9 to 750.75 kg CO₂-equivalent per MWh. Despite SMR’s lower production costs (USD 21–69/MWh), its environmental footprint is considerably higher. In contrast, methanation offers environmental benefits but remains economically uncompetitive (EUR 93.53–204.62/MWh). Both processes rely primarily on Ni-based catalysts, though recent developments in Ru-based and bimetallic systems have demonstrated improved performance. The review also examines operational challenges such as carbon deposition and catalyst deactivation. By framing these technologies through the shared lens of reversibility, this work outlines pathways toward integrated, efficient, and circular energy systems aligned with long-term sustainability and climate neutrality goals. Full article

Olive mill wastewater (OMW) is a highly polluting effluent rich in organic pollutant compounds derived from olive oil production. In this work, the steam reforming reaction of OMW (OMWSR) was performed in a traditional reactor at 400 °C and different pressures (1–4 bar) to treat and valorize this effluent. A commercial catalyst (Rh/Al₂O₃) was used as a reference sample and several new catalysts were prepared (Ni-Ru/Ce-SiO₂) using different preparation methods to study their effect on the activity and stability. The best-performing catalysts were also subjected to long-term operation experimental tests (24 h). It was observed that the preparation method used for the catalysts synthesis influenced the catalytic performance of the samples. In addition, temperature-programmed oxidation (TPO) analysis of the used catalyst showed the presence of carbon deposits: the results showed that periodic oxidative regeneration improved the catalyst stability and sustained H₂ production. Finally, it was verified that the Ni-Ru/Ce³ catalyst stood out during the experimental tests, exhibiting high catalytic activity along the stability test at 400 °C and 1 bar: H₂ yield always over 7 mol_H2·mol_OMW⁻¹ and total organic carbon (TOC) conversion always higher than 94%. Despite these promising results, further research is needed to assess the economic feasibility of scaling up the process. Additionally, future work could explore the development of catalysts with enhanced resistance to deactivation by carbon deposition. Full article

A rational design strategy for active sites on the catalyst surface can effectively enhance CO₂ reduction reaction (CO₂RR) selectivity. Transition metal atoms from the fourth (Sc–Ni) and fifth (Y–Mo, Ru–Pd) periods were doped onto the In₂S₂X (X = Se, Te) surface to control bimetallic active sites. The study showed that the d-band center’s position of the dopant atom significantly influences CO₂RR selectivity. Cations with positive d-band centers further from the Fermi level are more inclined towards CH₂O, while those with negative d-band centers closer to the Fermi level favor HCOOH; cations with d-band centers near the Fermi level exhibit a strong preference for CH₃OH. This study systematically elucidates the intrinsic mechanisms and offers a significant theoretical foundation for developing highly selective photocatalysts. Full article

One viable technical approach for achieving hydrogen-blended combustion in marine ammonia-fueled engines is to utilize online ammonia decomposition to produce hydrogen, which is then introduced into the engine for combustion. This work carried out ammonia decomposition experiments using various catalysts, examining the effects of temperature and space velocity on Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 and Ni/Ce_0.36Zr_0.64O₂ catalysts. Based on the experimental data obtained, the kinetic parameters of ammonia decomposition were fitted using four different models: mass action law, first-order reaction, Langmuir, and Temkin–Pyzhev kinetics across two catalysts, with the subsequent mechanistic analysis of catalytic reaction processes within the reactor. The results revealed that the NH₃ conversion rate of the Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 catalyst was superior to that of the Ni/Ce_0.36Zr_0.64O₂ catalyst, with temperature activity windows of 250–450 °C and 400–600 °C, respectively. Within the range of 2000–32,000 mL·g⁻¹·h⁻¹), an increase in space velocity led to a decrease in NH₃ conversion rate by approximately half. All four models were able to predict NH₃ conversion rates for the different catalysts with reasonable accuracy. The activation energies for Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 and Ni/Ce_0.36Zr_0.64O₂ catalysts were found to be 37.7 kJ·mol⁻¹ and 66 kJ·mol⁻¹, respectively. Targeting hydrogen requirements of 10–40% vol for ammonia engines, the corresponding catalytic temperatures for Ru/Ce_0.33Zr_0.58La_0.03Nd_0.03Pr_0.03O_2.09 and Ni/Ce_0.36Zr_0.64O₂ were above 267 °C and 500 °C, respectively. Full article

The design of efficient hydrogen evolution reaction (HER) catalysts to minimize reaction overpotentials plays a pivotal role in advancing water electrolysis and clean energy solutions. Ru-based catalysts, regarded as potential replacements for Pt-based catalysts, face stability challenges during catalytic process. The precise regulation of metal–support interactions effectively prevents Ru nanoparticle degradation while optimizing interfacial electronic properties, enabling the simultaneous enhancement of catalytic activity and stability. Herein, we design an amorphous/crystalline support and employ in situ replacement to develop a Ru-NiP_x-Ni structure. The crystalline Ni phase with ordered atomic arrangement ensures efficient charge transport, while the amorphous phase with unsaturated dangling bonds provides abundant anchoring sites for Ru nanoclusters. This synergistic structure significantly enhances HER performance, which attains overpotentials of 19 mV at 10 mA cm⁻² and 70 mV at 100 mA cm⁻² in 1 m KOH, with sustained operation exceeding 55 h at 100 mA cm⁻². Electrochemical impedance spectroscopy analysis confirms that the Ru-NiP_x-Ni structure not only has a high density of active centers for HER, but also reduces the charge transfer resistance at the electrode–electrolyte interface, which effectively enhances HER kinetics. This study presents new directions for designing high-efficiency HER catalysts. Full article

In this study, a sulfur-doped cobalt–iron catalyst (CoFeS/NF) was synthesized on a nickel foam (NF) substrate via a facile one-step electrodeposition method, and its performance in urea electrolysis for hydrogen production was systematically investigated. Sulfur doping induced significant morphology optimization, forming a highly dispersed nanosheet structure, which enhanced the specific surface area increase by 1.9 times compared with the undoped sample, exposing abundant active sites. Meanwhile, the introduction of sulfur facilitated electron redistribution at the surface modulated the valence states of nickel and cobalt, promoted the formation of high-valence Ni³⁺/Co³⁺, optimized the adsorption energy of the reaction intermediates, and reduced the charge transfer resistance. Electrochemical evaluations revealed that CoFeS/NF achieves a current density of 10 mA cm⁻² at a remarkably low potential of 1.18 V for the urea oxidation reaction (UOR), outperforming both the undoped catalyst (1.24 V) and commercial RuO₂ (1.35 V). In addition, the catalyst also exhibited excellent catalytic activity and long-term stability in the total urea decomposition process, which was attributed to the amorphous structure and the synergistic enhancement of corrosion resistance by sulfur doping. This study provides a new idea for the application of sulfur doping strategy in the design of multifunctional electrocatalysts, which promotes the coupled development of urea wastewater treatment and efficient hydrogen production technology. Full article

The aim of the present study was to clarify the influence of the thickness of the Pd/Cu membrane on the characteristics of biogas dry reforming (BDR) with aNi/Cr/Ru catalyst. We also clarified the impact of the reaction temperature, the molar ratio of CH₄:CO₂, the differential pressure between the reaction and sweep chambers, and the introduction of a sweep gas on the characteristics of a BDR reactor with a Pd/Cu membrane and a Ni/Cr/Ru catalyst. Through this study’s results, we clarify that the concentration of H₂ in the reaction chamber and the sweep chamber increases with the increase in the reaction temperature. In addition, this study clarifies that the highest concentration of H₂ in the reaction chamber and the sweep chamber can be obtained with a molar ratio of CH₄:CO₂ = 1.5:1. This study also clarifies that the highest concentration of H₂ can be obtained with a thickness of 40 μm, a molar ratio of CH₄:CO₂ = 1.5:1, and a differential pressure between the reaction chamber and the sweep chamber of 0 MPa without a sweep gas, which was 4890 ppmV in the reaction chamber and 38 ppmV in the sweep chamber. Under these conditions, CH₄ conversion, H₂ yield, and thermal efficiency were 75.0%, 0.214%, and 2.92%, respectively. Full article

Designing efficient and cost-effective electrocatalysts is crucial for the large-scale development of sustainable hydrogen energy. Amorphous catalysts hold great promise for application due to their structural flexibility and high exposure of active sites. We report a novel method for the in situ growth of amorphous CoNiRuO_x nanoparticle structures (CoNiRuO_x/NF) on a nickel foam substrate. In 1 m KOH, CoNiRuO_x/NF achieves a current density of 10 mA/cm² with a hydrogen evolution reaction (HER) overpotential of only 43 mV and remains stable for over 100 h at a current density of 100 mA/cm². An alkaline electrolyzer assembled with CoNiRuO_x/NF as the cathode delivers a current density 2.97 times higher than that of an IrO₂||Pt/C electrode pair at the potential of 2 V and exhibits excellent long-term durability exceeding 100 h. Experimental results reveal that the combined replacement and corrosion reactions facilitate the formation of the amorphous CoNiRuO_x structure. This work provides valuable insights for developing efficient and scalable amorphous catalysts. Full article