Search Results (22)

Improving the efficiency of photocatalysts for hydrogen production while minimizing the amount of noble metals used is a pressing issue in modern green energy. This study examines the effect of ultra-small Pt additives on increasing the efficiency of the CuO_x-dark TiO₂ photocatalyst used in the hydrogen evolution reaction (HER). Initially, Pt was photoreduced from the hydroxonitrate complex (Me₄N)₂[Pt₂(OH)₂(NO₃)₈] onto the surface of nanodispersed CuO_x powder obtained by pulsed laser ablation. Then, the obtained Pt-CuO_x particles were dispersed on the surface of highly defective dark TiO₂, so that the mass content of Pt in the samples varied in the range from 1.25 × 10⁻⁵ to 10⁻⁴. The prepared samples were examined using HRTEM, XRD, XPS, and UV-Vis DRS methods. It has been established that in the Pt-CuO_x particles, platinum is mainly present in the form of single atoms (SAs), both as Pt²⁺ (predominantly) and Pt⁴⁺ species, which should facilitate electron transfer and contribute to the manifestation of the strong metal–support interaction (SMSI) effect between SA Ptⁿ⁺ and CuO_x. In turn, in the Pt-CuO_x-dark TiO₂ samples, surface defects (O_v) and surface OH groups on dark TiO₂ particles act as “anchors”, promoting the spontaneous dispersion of CuO_x in the form of sub-nanometer clusters with the reduction of Cu²⁺ to Cu¹⁺ when localized near such O_v defects. During photocatalytic HER in aqueous glycerol solutions, irradiation was found to initiate a large number of catalytically active Pt⁰-CuO_x-O_v-dark TiO₂ centers, where the SMSI effect causes electron transfer from titania to SA Pt, thus promoting better separation of photogenerated charges. As a result, ultra-small additives of Pt led to up to a 1.34-fold increase in the amount of released hydrogen, while the maximum apparent quantum yield (AQY) reached 65%. Full article

Biomass gasification represents a pivotal technology for sustainable energy and chemical production, yet its efficiency and product quality are critically dependent on catalyst performance. This comprehensive review systematically synthesizes recent advancements in catalyst design, mechanistic insights, and process integration in biomass gasification. Firstly, it details the development and performance of catalysts in diverse categories, including metal-based catalysts, Ca-based catalysts, natural mineral catalysts, composite/supported catalysts, and emerging waste-derived catalysts. Secondly, this review delves into the fundamental catalytic reaction mechanisms governing key processes such as tar cracking/reforming, water–gas shift, and methane reforming. It further explores sophisticated strategies for catalyst structure optimization, focusing on pore structure/surface area control, strong metal–support interactions (SMSIs), alloying effects, nanodispersion, and crystal phase design. The critical challenges of catalyst deactivation mechanisms and the corresponding activation, regeneration strategies, and post-regeneration performance evaluation are thoroughly discussed. Thirdly, this review addresses the crucial integration of zero CO₂ emission concepts, covering in situ CO₂ adsorption/conversion, carbon capture and storage (CCS) integration, catalytic CO₂ reduction/valorization, multi-energy system synergy, and environmental impact/life cycle analysis (LCA). By synthesizing cutting-edge research, this review identifies key knowledge gaps and outlines future research directions towards designing robust, cost-effective, and environmentally benign catalysts for next-generation, carbon-neutral biomass gasification systems. Full article

Ru/TiO₂ catalysts are well known for their high activity in the hydrogenation of CO₂ to CH₄ (the Sabatier reaction). This activity is commonly attributed to strong metal–support interactions (SMSIs), associated with reducible oxide layers partly covering the Ru-metal particles. Moreover, isothermal rates of formation of CH₄ can be significantly enhanced by the exposure of Ru/TiO₂ to light of UV/visible wavelengths, even at relatively low intensities. In this study, we confirm the significant enhancement in the rate of formation of methane in the conversion of CO₂, e.g., at 200 °C from ~1.2 mol g_Ru⁻¹·h⁻¹ to ~1.8 mol g_Ru⁻¹·h⁻¹ by UV/Vis illumination of a hydrogen-treated Ru/TiO_x catalyst. The activation energy does not change upon illumination—the rate enhancement coincides with a temperature increase of approximately 10 °C in steady state (flow) conditions. In-situ DRIFT experiments, performed in batch mode, demonstrate that the Ru–CO absorption frequency is shifted and the intensity reduced by combined UV/Vis illumination in the temperature range of 200–350 °C, which is more significant than can be explained by temperature enhancement alone. Moreover, exposing the catalyst to either UV (predominantly exciting TiO₂) or visible illumination (exclusively exciting Ru) at small intensities leads to very similar effects on Ru–CO IR intensities, formed in situ by exposure to CO₂. This further confirms that the temperature increase is likely not the only explanation for the enhancement in the reaction rates. Rather, as corroborated by photophysical studies reported in the literature, we propose that illumination induces changes in the electron density of Ru partly covered by a thin layer of TiO_x, lowering the CO coverage, and thus enhancing the methane formation rate upon illumination. Full article

In conventionally used carbon-supported heterogeneous platinum catalysts for hydrogen evolution reaction (HER), low Pt utilization efficiency and poor stability, resulting from weak interactions with the carbon supports, are crucial issues. Here, we report a novel hierarchical structure of TiO_x nanoparticles embedded in porous carbon with the in situ growth of highly dispersed Pt on the TiO_x surface (Pt-TiO_x@C). The as-prepared Pt-TiO_x@C electrocatalyst showed excellent catalytic activity during HER with an overpotential of only 10 mV when the current density reached 10 mA cm⁻² and the mass activity was 9.24 A mg_Pt⁻¹ at an overpotential of 30 mV in 0.5 M H₂SO₄ solution, thus outperforming commercial Pt/C catalysts. Furthermore, it also exhibited highly stable catalytic activity over 10,000 CV cycles of an accelerated degradation test (ADT). This high HER activity and durability could be ascribed to the highly dispersed Pt feature and the strong metal–support interaction (SMSI) between Pt and TiO_x. This study also provides a simple and effective method for designing highly active and stable electrocatalysts. Full article

The traditional catalytic oxidation of carbon monoxide (CO) using metal oxide catalysts often requires either high temperatures (thermocatalysis) or ultraviolet light (UV) excitation (photocatalysis), limiting practical applications under ambient conditions. Our research aimed to develop a catalytic system capable of oxidizing CO to CO₂ at room temperature and in the dark. Using the Strong Metal–Support Interaction (SMSI) methodology, several titanium oxide (TiO₂)-complexed metals were prepared (Ag, Au, Pd, and Pt). The highest catalytic efficiency of CO oxidation at room temperature was demonstrated for the TiO₂-Pt complex. Therefore, this complex was further examined structurally and functionally. Two modes of operation were addressed. The first involved applying the catalytic system to remove CO from an individual’s environment (environmental system), while the second involved the installation of the catalysis chamber as a part of a personal protection unit (e.g., a mask). The catalytic activity exhibited a significant reduction in CO levels in both the environmental and personal protection scenarios. The practical application of the system was demonstrated through efficient CO oxidation in air emitted from a controlled fire experiment conducted in collaboration with the Israel Fire and Rescue Authority. Full article

Catalytic conversion of CO₂ to CO via the reverse water gas shift (RWGS) reaction has been identified as a promising approach for CO₂ utilization and mitigation of CO₂ emissions. Bare Pt shows low activity for the RWGS reaction due to its low oxophilicity, with few research works having concentrated on the inverse metal oxide/Pt catalyst for the RWGS reaction. In this work, MnO_x was deposited on the Pt surface over a SiO₂ support to prepare the MnO_x/Pt inverse catalyst via a co-impregnation method. Addition of 0.5 wt% Mn to 1 wt% Pt/SiO₂ improved the intrinsic reaction rate and turnover frequency at 400 °C by two and twelve times, respectively. Characterizations indicate that MnO_x partially encapsulates the surface of the Pt particles and the coverage increases with increasing Mn content, which resembles the concept of strong metal–support interaction (SMSI). Although the surface accessible Pt sites are reduced, new MnO_x/Pt interfacial perimeter sites are created, which provide both hydrogenation and C-O activation functionalities synergistically due to the close proximity between Pt and MnO_x at the interface, and therefore improve the activity. Moreover, the stability is also significantly improved due to the coverage of Pt by MnO_x. This work demonstrates a simple method to tune the oxide/metal interfacial sites of inverse Pt-based catalyst for the RWGS reaction. Full article

In the context of the growing human demand for green secondary energy sources, proton-exchange membrane water electrolysis (PEMWE) is necessary to meet the high-efficiency production of high-purity hydrogen required for proton-exchange membrane fuel cells (PEMFCs). The development of stable, efficient, and low-cost oxygen evolution reaction (OER) catalysts is key to promoting the large-scale application of hydrogen production by PEMWE. At present, precious metals remain irreplaceable in acidic OER catalysis, and loading the support body with precious metal components is undoubtedly an effective strategy to reduce costs. In this review, we will discuss the unique role of common catalyst-support interactions such as Metal-Support Interactions (MSIs), Strong Metal-Support Interactions (SMSIs), Strong Oxide-Support Interactions (SOSIs), and Electron-Metal-Support Interactions (EMSIs) in modulating catalyst structure and performance, thereby promoting the development of high-performance, high-stability, low-cost noble metal-based acidic OER catalysts. Full article

Precise regulation and control solar-light-driven charges photoexcited on photocatalysts for separation-transfer and target redox reactions is an attractive and challenging pathway toward sustainability. Herein, 0D/2D-3D Pt/In₂S₃ Schottky junction was fabricated for simultaneous selective phenylcarbinol conversion into value-added aldehydes and production of clean energy H₂ by directly utilizing photoexcited holes and electrons in one reaction system under mild reaction conditions. In contrast to pure water splitting and pure In₂S₃, the reaction thermodynamics and kinetics of H₂ evolution on the Pt/In₂S₃ were significantly enhanced. The optimized 0.3% Pt/In₂S₃ exhibited the highest and most stable photocatalytic activity with 22.1 mmol g⁻¹ h⁻¹ of H₂ production rate and almost 100% selectivity of benzaldehyde production. Notably, this dual-function photocatalysis also exhibited superiority in contrast to sacrificial-agent H₂ evolution reactions such as lactic acid, Na₂S, methanol and triethanolamine. The turnover frequency (TOF) could reach up to ~2394 h⁻¹. The Pt clusters anchored at the electron location and strong metal-support interactions (SMSI) between Pt and In₂S₃ synergistically improved the spatial charge separation and directional transportation (~90.1% of the charge transport efficiency could be achieved over the Pt/In₂S₃ hybrid), and thus result in significant enhancement of photocatalytic H₂ evolution with simultaneous benzaldehyde production. Full article

It has been found that the electrocatalytic properties of metallic nanoparticles supported on transition metal oxides are affected by the existing strong metal–support interaction (SMSI). Herein, the effects of SMSI on the electrocatalysis of the hydrogen evolution reaction (HER) were investigated in acid electrolyte by using Pt and Ag nanoparticles supported on carbon and titanium oxide (TiO₂). High-resolution transmission electron microscopy (HR–TEM) images showed that Pt and Ag nanoparticles present a spherical shape at the TiO₂ support and an average size distribution of around 4.5 nm. The X-ray photoelectron spectroscopy (XPS) results for Pt/TiO₂/C and Ag/TiO₂/C evidenced higher amounts of surface oxides in the metallic particles, when compared to the materials supported on carbon. Consistently, electrode polarization and electrochemical impedance results revealed that both metal–TiO₂ and metal–C-supported catalysts were more active in catalyzing the HER than the corresponding carbon-supported materials, with Pt presenting better results. These differences in the HER activities were related to the electronic effects of the TiO₂/C substrate on the Pt and Ag metals, introduced by strong metal-support (SMSI) in the metal–TiO₂/C catalysts. Full article

Although clean energy generation utilizing the Oxygen Reduction Reaction (ORR) can be considered a promising strategy, this approach remains challenging by the dependence on high loadings of noble metals, mainly Platinum (Pt). Therefore, efforts have been directed to develop new and efficient electrocatalysts that could decrease the Pt content (e.g., by nanotechnology tools or alloying) or replace them completely in these systems. The present investigation shows that high catalytic activity can be reached towards the ORR by employing 1.8 ± 0.7 nm Ir nanoparticles (NPs) deposited onto MnO₂ nanowires surface under low Ir loadings (1.2 wt.%). Interestingly, we observed that the MnO₂-Ir nanohybrid presented high catalytic activity for the ORR close to commercial Pt/C (20.0 wt.% of Pt), indicating that it could obtain efficient performance using a simple synthetic procedure. The MnO₂-Ir electrocatalyst also showed improved stability relative to commercial Pt/C, in which only a slight activity loss was observed after 50 reaction cycles. Considering our findings, the superior performance delivered by the MnO₂-Ir nanohybrid may be related to (i) the significant concentration of reduced Mn³⁺ species, leading to increased concentration of oxygen vacancies at its surface; (ii) the presence of strong metal-support interactions (SMSI), in which the electronic effect between MnO_x and Ir may enhance the ORR process; and (iii) the unique structure comprised by Ir ultrasmall sizes at the nanowire surface that enable the exposure of high energy surface/facets, high surface-to-volume ratios, and their uniform dispersion. Full article

A series of rutile TiO₂-supported Ni catalysts with varying Ni sizes were prepared and reduced at 650 °C to explore the effect of Ni size on the strong metal–support interactions (SMSI) and its consequences on the hydrodeoxygenation (HDO) of m-cresol at 350 °C and atmospheric pressure. When the Ni size increases from 4 to 29.1 nm, the SMSI becomes stronger, e.g., the thickness of the TiO_x overlayer and the coverage extent of TiO_x on the Ni particle surface increase. Direct deoxygenation to toluene is the dominant pathway on Ni/TiO₂ catalysts with varying Ni loadings, with almost no CH₄ being formed. These results indicate that the TiO_x overlayer significantly alters the property of Ni. That is, the C-C hydrogenolysis activity on bare Ni is completely inhibited due to SMSI, while the deoxygenation activity is improved at the Ni-TiO_x interfacial perimeter sites. Meanwhile, the turnover frequency of HDO on small Ni particles of 4 nm is > 2 times higher than that on large Ni particles of 29.1 nm, indicating that the small Ni particle with moderate SMSI appears to be optimal for the direct deoxygenation of m-cresol to toluene. The results suggest HDO activity may be enhanced by tuning the metal particle size and SMSI degree. Full article

The strong metal–support interaction (SMSI) between the three components in Au/CeO₂–Mg(OH)₂ can be controlled by the relative composition of CeO₂ and Mg(OH)₂ and by the calcination temperature for the direct oxidative esterification of methacrolein (MACR) with methanol to methyl methacrylate (MMA). The composition ratio of CeO₂ and Mg(OH)₂ in the catalyst affects the catalytic performance dramatically. An Au/CeO₂ catalyst without Mg(OH)₂ esterified MACR to a hemiacetal species without MMA production, which confirmed that Mg(OH)₂ is a prerequisite for successful oxidative esterification. When Au/Mg(OH)₂ was used without CeO₂, the direct oxidative esterification of MACR was successful and produced MMA, the desired product. However, the MMA selectivity was much lower (72.5%) than that with Au/CeO₂–Mg(OH)₂ catalysts, which have an MMA selectivity of 93.9–99.8%, depending on the relative composition of CeO₂ and Mg(OH)₂. In addition, depending on the calcination temperature, the crystallinity of the CeO₂–Mg(OH)₂ and the surface acidity/basicity can be remarkably changed. Consequently, the Au-nanoparticle-supported catalysts exhibited different MACR conversions and MMA selectivities. The catalytic behavior can be explained by the different metal–support interactions between the three components depending on the composition ratio of CeO₂ and Mg(OH)₂ and the calcination temperature. These differences were evidenced by X-ray diffraction, X-ray photoelectron spectroscopy, and CO₂ temperature-programmed desorption. The present study provides new insights into the design of SMSI-induced supported metal catalysts for the development of multifunctional heterogeneous catalysts. Full article

The discoveries and development of the oxidative strong metal–support interaction (OMSI) phenomena in recent years not only promote new and deeper understanding of strong metal–support interaction (SMSI) but also open an alternative way to develop supported heterogeneous catalysts with better performance. In this review, the brief history as well as the definition of OMSI and its difference from classical SMSI are described. The identification of OMSI and the corresponding characterization methods are expounded. Furthermore, the application of OMSI in enhancing catalyst performance, and the influence of OMSI in inspiring discoveries of new types of SMSI are discussed. Finally, a brief summary is presented and some prospects are proposed. Full article

Au nanoparticles bound to crystalline CeO₂ nanograins that were dispersed on the nanoplate-like Mg(OH)₂, denoted as Au/CeO₂-Mg(OH)₂, were developed as the highly active and selective multifunctional heterogeneous catalyst for direct oxidative esterification of aldehydes with alcohols to produce alkyl esters under base-free aerobic conditions using oxygen or air as the green oxidants. Au/CeO₂-Mg(OH)₂ converted 93.3% of methacrylaldehyde (MACR) to methyl methacrylate (MMA, monomer of poly(methyl methacrylate)) with 98.2% selectivity within 1 h, and was repeatedly used over eight recycle runs without regeneration. The catalyst was extensively applied to other aldehydes and alcohols to produce desirable alkyl esters. Comprehensive characterization analyses revealed that the strong metal–support interaction (SMSI) among the three catalytic components (Au, CeO₂, and Mg(OH)₂), and the proximity and strong contact between Au/CeO₂ and the Mg(OH)₂ surface were prominent factors that accelerated the reaction toward a desirable oxidative esterification pathway. During the reaction, MACR was adsorbed on the surface of CeO₂-Mg(OH)₂, upon which methanol was simultaneously activated for esterifying the adsorbed MACR. Hemiacetal-form intermediate species were subsequently produced and oxidized to MMA on the surface of the electron-rich Au nanoparticles bound to partially reduced CeO_2−x with electron-donating properties. The present study provides new insights into the design of SMSI-induced supported-metal-nanoparticles for the development of novel, multifunctional, and heterogeneous catalysts. Full article

In this study, we address the catalytic performance of variously sized Pt nanoparticles (NPs) (from 1.7 to 2.9 nm) supported on magnéli phase titanium oxide (MPTO, Ti₄O₇) along with commercial solid type carbon (VXC-72R) for oxygen reduction reaction (ORR). Key idea is to utilize a robust and electrically conductive MPTO as a support material so that we employed it to improve the catalytic activity and durability through the strong metal-support interaction (SMSI). Furthermore, we increase the specific surface area of MPTO up to 61.6 m² g⁻¹ to enhance the SMSI effect between Pt NP and MPTO. After the deposition of a range of Pt NPs on the support materials, we investigate the ORR activity and durability using a rotating disk electrode (RDE) technique in acid media. As a result of accelerated stress test (AST) for 30k cycles, regardless of the Pt particle size, we confirmed that Pt/MPTO samples show a lower electrochemical surface area (ECSA) loss (<20%) than that of Pt/C (~40%). That is explained by the increased dissolution potential and binding energy of Pt on MPTO against to carbon, which is supported by the density functional theory (DFT) calculations. Based on these results, we found that conductive metal oxides could be an alternative as a support material for the long-term fuel cell operation. Full article