Search Results (76)

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

Mössbauer spectroscopy can be advantageous for studying catalysts. In particular, its use in in situ studies can provide unique access to structural features. However, special attention must be paid to the interpretation of data, since in most studies, the samples are not perfectly homogeneous. Balance and compromise should be found between the refinement of evaluations by extracting and interpreting data from spectra, while also considering the presence of possible inhomogeneities in samples. In this review, examples of studies on two types of catalysts are presented, from which, despite possible inhomogeneities, clear statements can be derived. The first example pertains to selected iron-containing microporous zeolites (with ⁵⁷Fe Mössbauer spectroscopy), from which unique information is collected on the coordination of iron ions. The second example is related to studies on supported PtSn alloy particles (with ¹¹⁹Sn probe nuclei), from which reversible modifications of the tin component due to interactions with the reaction partners are revealed. Full article

In this article, Pt-Sn_xO_y hybrid nanoparticles encaged in porous silica nanospheres (Pt-Sn_xO_y@PSNs) were prepared by using 1-dodecanethiol (C₁₂-SH) as a coordination agent to confine Pt and Sn ions in a microemulsion system, which is formed by cetyltrimethylammonium bromide (CTAB) and C₁₂-SH as co-surfactants in water. Compared with Pt@PSNs, when different molar ratios of Sn_xO_y were introduced into Pt@PSNs to form Pt-Sn_xO_y@PSNs, the catalytic efficiency of 4-nitrophenol (4-NP) reduction with NaBH₄ can be significantly enhanced. At molar ratios of 4-NP/Pt of 150/1, the 4-NP conversion reached 100% over Pt-Sn_xO_y@PSNs with Pt/Sn molar ratios of 1/0.75 in 8 min. This catalytic performance showed a slight decrease after six reaction cycles. This enhanced catalytic efficiency can be ascribed to the synergistic effect between Pt and Sn_xO_y, and the protection of porous silica nanostructures can effectively improve the stability of the catalyst. Full article

Sn-doped TiO₂–carbon composites were identified as promising multifunctional supports for Pt electrocatalysts, in which the oxide component enhances resistance against corrosion and strong metal–support interactions at the Pt-oxide boundary ensure high stability for the Pt nanoparticles. This work is devoted to the study of the influence of preliminary functionalization of the carbon on the properties of Pt/Ti_0.9Sn_0.1O₂–C catalysts. The structural, compositional and morphological differences between the samples prepared using functionalized or unmodified carbon, as well as the effect of carbon pre-modification on the electrocatalytic behavior of the synthesized Pt catalysts, were investigated using TEM, XRD, XPS, nitrogen adsorption and electrochemical measurements. The presence of oxygen-containing functional groups on carbon treated with HNO₃ and glucose leads to the formation of a homogeneous coating of the carbon with dispersed crystallites of mixed oxide. Elemental mapping revealed the proximity of Sn species with highly dispersed (2–3 nm) Pt particles. Notably, the electrochemical results indicated enhanced activity in CO electrooxidation for both functionalized and unmodified carbon-containing catalysts. An improvement in the 10,000-cycle long-term stability of the catalyst prepared using functionalized carbon was evident compared to the catalyst with untreated carbon or reference Pt/C. Full article

To achieve the “double carbon” goal, it is urgent to reform the energy system. The oxygen evolution reaction (OER) is a vital semi-reaction for many new energy-storage and conversion devices. Metal nanoparticles embedded in heteroatom-doped carbon materials prepared by the pyrolyzing of metal–organic frameworks (MOFs) have been a key route to obtain high-performance electrochemical catalysts. Herein, a nanocatalyst embedding Ni nanoparticles into S- and N-co-doped carbon nanoplate (Ni NPs@SN-CNP) has been synthesized by pyrolysis of a Ni-MOF precursor. The prepared Ni NPs@SN-CNP exhibits superior oxygen evolution performance with an overpotential of 256 mV to attain 10 mA cm⁻² and a low Tafel slope value of 95 mV dec⁻¹. Moreover, a self-assembled overall-water-splitting cell with Ni NPs@SN-CNP/NF||Pt-C/NF achieves a low potential of 1.56 V at 10 mA cm⁻² and a high cycling stability for at least 10 h. The improvement in this performance is benefit from its large surface area, unique morphology, and the nanostructure of the electrocatalyst. This study presents a novel and simple approach to designing high-performance OER catalysts. Full article

This study explores the development of core–shell electrocatalysts for efficient glycerol oxidation in alkaline media. Carbon-supported M@Pt/C (M = Co, Ni, Sn) catalysts with a 1:1 atomic ratio of metal (M) to platinum (Pt) were synthesized using a facile sodium borohydride reduction method. The analysis confirmed the formation of the desired core–shell structure, with Pt dominating the surface as evidenced by energy-dispersive X-ray spectroscopy (EDS). X-ray diffraction (XRD) revealed the presence of a face-centered cubic (fcc) Pt structure for Co@Pt/C and Ni@Pt/C. Interestingly, Sn@Pt/C displayed a PtSn alloy formation indicated by shifted Pt peaks and the presence of minor Sn oxide peaks. Notably, no diffraction peaks were observed for the core metals, suggesting their amorphous nature. Electrocatalytic evaluation through cyclic voltammetry (CV) revealed superior glycerol oxidation activity for Co@Pt/C compared to all other catalysts. The maximum current density followed the order Co@Pt/C > Ni@Pt/C > Sn@Pt/C > Pt/C. This highlights the effectiveness of the core–shell design in enhancing activity. Furthermore, Sn@Pt/C displayed remarkable poisoning tolerance attributed to a combined effect: a bifunctional mechanism driven by Sn oxides and an electronic effect within the PtSn alloy. These findings demonstrate the significant potential of core–shell M@Pt/C structures for designing highly active and poisoning-resistant electrocatalysts for glycerol oxidation. The presented approach paves the way for further development of optimized catalysts with enhanced performance and stability aiming at future applications in direct glycerol fuel cells. Full article

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

This paper presents the results of a study on the characteristics of semiconductor sensors based on thin SnO₂ films modified with antimony, dysprosium, and silver impurities and dispersed double Pt/Pd catalysts deposited on the surface to detect carbon monoxide (CO). An original technology was developed, and ceramic targets were made from powders of Sn-Sb-O, Sn–Sb-Dy–O, and Sn–Sb-Dy-Ag–O systems synthesized by the sol–gel method. Films of complex composition were obtained by RF magnetron sputtering of the corresponding targets, followed by technological annealing at various temperatures. The morphology of the films, the elemental and chemical composition, and the electrical and gas-sensitive properties were studied. Special attention was paid to the effect of the film composition on the stability of sensor parameters during long-term tests under the influence of CO. It was found that different combinations of concentrations of antimony, dysprosium, and silver had a significant effect on the size and distribution of nanocrystallites, the porosity, and the defects of films. The mechanisms of degradation under prolonged exposure to CO were examined. It was established that Pt/Pd/SnO₂:0.5 at.% Sb film with optimal crystallite sizes and reduced porosity provided increased stability of carbon monoxide sensor parameters, and the response to the action of 100 ppm carbon monoxide was G₁/G₀ = 2–2.5. Full article

Constructing highly efficient catalysts for the degradation of organic pollutants driven by solar light in aquatic environments is a promising and green strategy. In this study, a novel hexagonal sheet-like Pt/SnS₂ heterojunction photocatalyst is successfully designed and fabricated using a hydrothermal method and photodeposition process for photocatalytic tetracycline (TC) degradation. The optimal Pt/SnS₂ hybrid behaves with excellent photocatalytic performance, with a degradation efficiency of 91.27% after 120 min, a reaction rate constant of 0.0187 min⁻¹, and durability, which can be attributed to (i) the formation of a metal/semiconductor interface field caused by loading Pt nanoparticles (NPs) on the surface of SnS₂, facilitating the separation of photo-induced charge carriers; (ii) the local surface plasmon resonance (LSPR) effect of Pt NPs, extending the light absorption range; and (iii) the sheet-like structure of SnS₂, which can shorten the transmission distance of charge carriers, thereby allowing more electrons (e⁻) and holes (h⁺) to transfer to the surface of the catalyst. This work provides new insights with the utilization of sheet-like structured materials for highly active photocatalytic TC degradation in wastewater treatment and environmental remediation. Full article

Autothermal oxidative coupling of methane (OCM) is a highly attractive approach for methane utilization. If platinum-based catalysts are operated in short-contact-time reactors with high space velocities, high methane conversion can be achieved. Using a 1 wt.% Pt/Al₂O₃ catalyst as a benchmark, the present study elucidates how different dopants, namely Ni, Sn, and V₂O₅, affect the OCM reaction. Kinetic catalyst tests reveal that acetylene (C₂H₂) is the predominant C₂ product, irrespective of the catalyst formulation or operation conditions. Furthermore, the use of bimetallic catalysts allows either for the maintenance or even the improvement of the C₂ selectivity during OCM, which is attributed to synergistic effects that occur when expensive Pt is partially replaced by cheaper dopants. In particular, the 1 wt.% Pt/Al₂O₃ reference catalyst yielded a maximum C₂ selectivity of 8.2%, whereas the best-performing doped sample 0.25 wt.% Pt 0.75 wt.% V₂O₅/Al₂O₃ yielded a total C₂ selectivity of 11.3%. Full article

The dehydrogenation of n-butane to butenes is a crucial process for producing valuable petrochemical intermediates. This study explores the role of oxyphilic metal promoters (Sn, Zn, and Ga) in enhancing the performance and stability of Pt@MFI catalysts for n-butane dehydrogenation. The presence of Sn in the catalyst inhibits the agglomeration of Pt clusters, maintaining their subnanometric particle size. PtSn@MFI exhibits superior stability and selectivity for butenes while suppressing cracking reactions, with selectivity for C1–C3 products as low as 2.1% at 550 °C compared to over 30.5% for Pt@MFI. Using a combination of high-angle annular dark-field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Raman spectroscopy, we examined the structural and electronic properties of the catalysts. Our findings reveal that Zn tends to consume hydroxyl groups and substitute framework sites, and Ga induces more defective sites in the zeolite structure. In contrast, the interaction between SnO_x and the zeolite framework does not depend on reactions with hydroxyl groups. The incorporation of Sn significantly prevents Pt particle agglomeration, maintaining smaller Pt particle sizes and reducing coke formation compared to Zn and Ga promoters. Theoretical calculations showed that Sn increases the positive charge on Pt clusters, enhancing their interaction with the zeolite framework and reducing sintering, albeit with a slight increase in the energy barrier for C-H activation. These results underscore the dual benefits of Sn as a promoter, offering enhanced structural stability and reduced coke formation, thus paving the way for the rational design of more effective and durable catalysts for alkane dehydrogenation and other high-value chemical processes. Full article

Developing an OER electrocatalyst that balances high performance with low cost is crucial for widely adopting PEM water electrolyzers. Ru-based catalysts are gaining attention for their cost-effectiveness and high activity, positioning them as promising alternatives to Ir-based catalysts. However, Ru-based catalysts can be prone to oxidation at high potentials, compromising their durability. In this study, we utilize a simple synthesis method to synthesize a SnO₂, Nb₂O₅, and RuO₂ composite catalyst (SnO₂/Nb₂O₅@RuO₂) with multiple interfaces and abundant oxygen vacancies. The large surface area and numerous active sites of the SnO₂/Nb₂O₅@RuO₂ catalyst lead to outstanding acidic oxygen evolution reaction (OER) performance, achieving current densities of 10, 50, and 200 mA cm⁻² at ultralow overpotentials of 287, 359, and 534 mV, respectively, significantly surpassing commercial IrO₂. Moreover, incorporating Nb₂O₅ into the SnO₂/Nb₂O₅@RuO₂ alters the electronic structure at the interfaces and generates a high density of oxygen vacancies, markedly enhancing durability. Consequently, the membrane electrode composed of SnO₂/Nb₂O₅@RuO₂ and commercial Pt/C demonstrated stable operation in the PEM cell for 25 days at an industrial current density of 1 A cm⁻². This research presents a convenient approach for developing a highly efficient and durable Ru-based electrocatalyst, underscoring its potential for proton exchange membrane water electrolysis. Full article

In this study, a PtSn/Al₂O₃ catalyst with bimetallic uniform distribution in the sphere was synthesized. The PDH performance and characterization analyses, such as with FTIR, XPS, and NH₃-TPD, were investigated. The effects of acid on the PDH performance were analyzed. Citric acid (CA) acted as a competing adsorbent in the preparation process of the PtSn/Al₂O₃ catalyst to synthesize the uniform catalyst. Water washing and alkali-treated samples were also studied. SEM line scanning revealed that increased the apparent concentration of Pt metal from 0.23 to 0.30 with citric acid. In contrast to the fresh PtSn/Al₂O₃ catalyst, the addition of citric acid increased the PDH selectivity from 74% to 93%. After alkali or water washing treatments, the catalyst’s selectivity further increased to 96%. Strong acid sites promoted the breaking of C–C bonds during the PDH reaction, resulting in more methane and ethylene byproducts, and decreased catalyst selectivity for fresh PtSn/Al₂O₃. From the PDH reaction thermodynamic analysis, a relatively sub-atmospheric pressure environment with a lower propane pressure could be the reasonable choice. Full article

In the propane dehydrogenation process, the structure and catalytic performance stability of the catalyst are determined by its regeneration process, which includes oxidation of coke and oxychlorination to redisperse the supported metal particles. A commercial Pt-Sn catalyst was used in this work to investigate the impact of oxidation temperature on oxychlorination performance. The catalysts after oxidation and oxychlorination were characterized by H₂-TPR, CO-DRIFTS, HAADF-STEM, XPS, and CO chemisorption. It was found that mild sintering of Pt occurred during oxidation in the temperature range of 550–650 °C, and the catalyst could be fully restored in the subsequent oxychlorination treatment. Upon oxidation of the catalyst at 700 °C, a severe aggregation of Pt and SnOx could be observed, and the catalyst could not be fully regenerated under the given oxychlorination conditions. However, PDH catalyst deactivation caused by sintering is not irreversible. By tailoring the oxychlorination conditions, the detrimental effect of high oxidation temperature on regeneration could be ruled out. During the oxidation and oxychlorination treatment, the metal tends to migrate to anchor on sites with stronger metal–support interaction, which was helpful for enhancing the catalytic activity. Full article

Proton-exchange-membrane hydrogen fuel cells (PEMFCs) are an important energy device for achieving a sustainable hydrogen society. Carbon-based catalysts used in PEMFCs’ cathode can degrade significantly during operation-voltage shifts due to the carbon deterioration. The longer lifetime of the system is necessary for the further wide commercialization of PEMFCs. Therefore, carbon-free catalysts are required for PEMFCs. In this study, highly crystallized conducting Sb-doped SnO₂ (Sb-SnO₂) nanoparticles (smaller than 7 nm in size) were synthesized using an ozone-assisted hydrothermal synthesis. Pt nanoparticles were loaded on Sb-SnO₂ supporting particles by polyol method to be “Pt/Sb-SnO₂ catalyst”. The Pt/Sb-SnO₂ catalyst showed a high oxygen reduction reaction (ORR) mass activity (178.3 A g_-Pt⁻¹ @ 0.9 V), compared to Pt/C (149.3 A g_-Pt⁻¹ @ 0.9 V). In addition, the retention ratio from the initial value of electrochemical surface area (ECSA) during 100,000-voltage cycles tests between 1.0 V and 1.5 V, Pt/SnO₂ and Pt/Sb-SnO₂ catalyst exhibited higher stability (90% and 80%), respectively, than that of Pt/C catalyst (47%). Therefore, the SnO₂ and Sb-SnO₂ nanoparticles synthesized using this new ozone-assisted hydrothermal method are promising as carbon-free catalyst supports for PEMFCs. Full article