Search Results (536)

Herein, α-MnO₂-supported Pt-Pd bimetal (xPd-yPt/α-MnO₂; x and y are the weight loadings (wt%) of Pd and Pt, respectively; x = 0, 0.23, 0.47, 0.93, and 0.92 wt%; and y = 0.91, 0.21, 0.46, 0.89, and 0 wt%) catalysts were prepared using the polyvinyl alcohol-protected NaBH₄ reduction method. The physicochemical properties of the catalysts were determined by means of various techniques and their catalytic activities for toluene oxidation were evaluated. It was found that among the xPd-yPt/α-MnO₂ samples, 0.93Pd-0.89Pt/α-MnO₂ showed the best catalytic performance, with the toluene oxidation rate at 156 °C (r_cat) and space velocity = 60,000 mL/(g h) being 6.34 × 10⁻⁴ mol/(g s), much higher than that of 0.91Pt/α-MnO₂ (1.31 × 10⁻⁴ mol/(g s)) and that of 0.92Pd/α-MnO₂ (6.13 × 10⁻⁵ mol/(g s)) at the same temperature. The supported Pd-Pt bimetallic catalysts possessed higher Mn³⁺/Mn⁴⁺ and O_ads/O_latt molar ratios, which favored the enhancement in catalytic activity of the supported Pd-Pt bimetallic catalysts. Furthermore, the 0.47Pd-0.46Pt/α-MnO₂ sample showed better resistance to sulfur dioxide poisoning. The partial deactivation of 0.47Pd-0.46Pt/α-MnO₂ was attributed to the formation of sulfate species on the sample surface, which covered the active site of the sample, thus decreasing its toluene oxidation activity. In addition, the in situ DRIFTS results demonstrated that benzaldehyde and benzoate were the intermediate products of toluene oxidation. Full article

The methanol oxidation reaction (MOR) of direct methanol fuel cells (DMFCs) is limited by the slow kinetic process and high reaction energy barrier, significantly restricting the commercial application of DMFCs. Therefore, developing MOR catalysts with high activity and stability is very important. In this paper, oxygen-functionalised activated carbon (FAC) with controllable oxygen-containing functional groups was prepared by adjusting the volume ratio of H₂SO₃/HNO₃ mixed acid, and Pd/AC and Pd/FAC catalysts were synthesised via the hydrazine hydrate reduction method. A series of characterisation techniques and electrochemical performance tests were used to study the catalyst. The results showed that when V(H₂SO₃):V(HNO₃) = 2:3, more defects were generated on the surface of the AC, and more oxygen-containing functional groups represented by C=O and C–OH were attached to the surface of the support, which increased the anchor sites of Pd and improved the dispersion of Pd nanoparticles (Pd NPs) on the support. At the same time, the mass–specific activity of Pd/FAC for MOR was 2320 mA·mg_Pd, which is 1.5 times that of Pd/AC, and the stability was also improved to a certain extent. In situ infrared spectroscopy further confirmed that oxygen functionalisation treatment promoted the formation and transformation of *COOH intermediates, accelerated the transformation of CO_L into CO_B, reduced the poisoning of CO_ads species adsorbed to the catalyst, optimised the reaction path and improved the catalytic kinetic performance. Full article

Supported Pd-based catalysts have been widely applied in the hydrogenation of specific functional groups. Recent trends have focused on employing Pd-based heterogeneous catalysts supported on inorganic nanotubes, wherein inner surface functionalization modulates both palladium nanoparticle (Pd-NP) dispersion and the interaction between reactants and the catalyst surface, thereby influencing catalytic properties. This study aims to develop a catalytic system using amine-lumened halloysite nanotubes immobilizing Pd-NPs (Pd/HNTA) as catalysts for hydrogenation reactions. The formation of Pd-NPs within the organo-functionalized lumen—modified by 3-aminopropyltrimethoxysilane—is confirmed by transmission electron microscopy (TEM) imaging, which reveals a particle size of 2.2 ± 0.4 nm. For comparison, Pd-NPs supported on pristine halloysite (Pd/HNTP) were used as control catalysts, displaying a metal particle size of 2.8 ± 0.8 nm and thereby demonstrating the effect of organic functionalization on the halloysite nanotubes. Both catalysts were employed in the hydrogenation of furfural (FUR) and nitrobenzene (NB) as model reactions. Pd/HNTA demonstrated superior catalytic performance for both substrates, with TOF values of 880 h⁻¹ for FUR and 946 h⁻¹ for NB, and selectivities exceeding 98% for tetrahydrofurfuryl alcohol (THFOH) and aniline (AN), respectively. However, recyclability studies displayed that Pd/HNTA was deactivated at the 10 catalytic cycles during the hydrogenation of FUR, whereas, in the hydrogenation of NB, 5 catalytic cycles were achieved with maximum conversion and selectivity at 360 min. These results revealed that the liquid-phase environment plays a pivotal role in catalyst stability. In the hydrogenation of NB, the coproduction of H₂O adversely affects the interaction between the Pd particles and the inner amine-modified surface, increasing the deactivation of the catalyst with reuse. Thus, the Pd/HNTA catalyst holds significant promise for the development of noble-metal-based catalysts and their application in the transformation of other reducible organic functional groups via hydrogenation reaction. Full article

The rational development of single-atom catalysts (SACs) for selective formic acid dehydrogenation (FAD) requires an atomic-scale understanding of metal–support interactions and electronic modulation. In this study, spin-polarized density functional theory (DFT) calculations were performed to systematically examine platinum-group SACs anchored on graphitic carbon nitride (g-C₃N₄). The findings reveal that Pd and Au SACs exhibit superior selectivity toward the dehydrogenation pathway, lowering the free energy barrier by 1.42 eV and 1.39 eV, respectively, compared to the competing dehydration route. Conversely, Rh SACs demonstrate limited selectivity due to nearly equivalent energy barriers for both reaction pathways. Stability assessments indicate robust metal–support interactions driven by d–p orbital hybridization, while a linear correlation is established between the d-band center position relative to the Fermi level and catalytic selectivity. Additionally, charge transfer (ranging from 0.029 to 0.467 e) substantially modulates the electronic structure of the active sites. These insights define a key electronic descriptor for SAC design and offer a mechanistic framework for optimizing selective hydrogen production. Full article

The present study aims to investigate a Pd catalyst on a complex multi-oxide medium-entropy support interlayer La₂O₃-CeO₂-ZrO₂-Al₂O₃ and its possible use as catalysts for methane abatement applications. The low-temperature N₂-adsorption, XRD, TEM, XPS, TPD, and TPR techniques were used to characterize the catalyst. The palladium deposition on the supports leads to the formation of PdO. After the catalytic tests, the metal-Pd phase was observed. The complete oxidation of methane on Pd/La-Ce-Zr-Al catalyst takes place at temperatures above 250 °C, and in the presence of water vapor, the reaction temperature increases to about 70 °C. The careful choice of constituent oxides provides a balance between structural stability and flexibility. The alumina and lanthanum oxide ensure the high specific surface area, while the simultaneous presence of zirconia and ceria leads to the formation of a mixed-oxide phase able to interact with palladium ions by incorporating and de-incorporating them at different conditions. The mechanism of Mars–van Kerevelen was considered as the most probable for the reaction of complete methane oxidation. The possibility of the practical application of Pd-modified La-Ce-Zr-Al catalyst is evaluated. The use of a mix of multiple rare and abundant oxides makes the proposed catalyst a cost-effective alternative. Full article

Platinum- and/or palladium-containing silica-based supports were applied for the selective catalytic reduction of NO_x with hydrogen (H₂-SCR-DeNO_x). To obtain enhanced activity and N₂ selectivity below 150 °C, we varied the type and loading of noble metals (Pt and Pd both individually and paired, 0.1–1.0 wt.-%), silica-containing supports (ZrO₂/SiO₂, ZrO₂/SiO₂/Al₂O₃, Al₂O₃/SiO₂/TiO₂), as well as the H₂ concentration in the feed (2000–4000 ppm). All of these contributed to enhancing N₂ selectivity during H₂-SCR-DeNO_x over the (0.5 wt.-%)Pt/Pd/ZrO₂/SiO₂ catalyst in the presence of 10 vol.-% of O₂. H₂ was completely consumed at 150 °C. A comparison of the catalytic results obtained during H₂-SCR-DeNO_x,(H₂-)NH₃-SCR-DeNO_x, as well as stop-flow H₂-SCR-DeNO_x and temperature-programmed studies, revealed that in the temperature range between 150 and 250 °C, the continuously coupled or overlaying mechanism of NO reduction by hydrogen and ammonia based on NH₃ formation at lower temperatures, which is temporarily stored at the acid sites of the support and desorbed in this temperature range, could be postulated. Full article

This study explores the selective hydrogenation of cinnamaldehyde using a series of metal catalysts supported on reduced graphene oxide (rGO) and conventional activated carbon (AC). Catalysts based on Pt, Pd, Rh, Ru, and Co were synthesized with controlled metal loading and characterized by XRD, SEM-EDS, XRF, and TEM. Among all tested materials, Pd supported on rGO synthesized via the Tour method (Pd/rTOGO) exhibited the highest catalytic activity, achieving 62% conversion of cinnamaldehyde and superior selectivity toward hydrocinnamaldehyde (HCAL). The support material had a significant influence on performance, especially for Pd catalysts, where 2D rGO outperformed 3D AC in both conversion and selectivity. In contrast, other metals (Pt, Rh, Ru, Co) showed only modest activity and limited selectivity tuning via support choice. Notably, GC-MS analysis revealed the formation of a previously underreported side product, 3-isopropoxy-propan-1-yl benzene (ether), likely formed via reductive etherification in isopropanol. The combined kinetic and selectivity data enabled the proposal of reaction pathways, including rapid transformation of cinnamylalcohol (COL) to hydrocinnamal alcohol (HCOL) and HCAL to ether. These findings emphasize the importance of support structure and surface functionality, particularly in 2D carbon materials, for designing efficient and selective hydrogenation catalysts. Full article

The electrochemical CO₂ reduction reaction (eCO₂RR), driven by renewable energy, represents a promising strategy for mitigating atmospheric CO₂ levels while generating valuable fuels and chemicals. Its practical implementation hinges on the development of highly efficient electrocatalysts. In this study, a novel dual-metal atomic catalyst (DAC), composed of niobium and palladium single atoms anchored on a ferroelectric α-In₂Se₃ monolayer (Nb-Pd@In₂Se₃), is proposed based on density functional theory (DFT) calculations. The investigation encompassed analyses of structural and electronic characteristics, CO₂ adsorption configurations, transition-state energetics, and Gibbs free energy changes during the eCO₂RR process, elucidating a synergistic catalytic mechanism. The Nb-Pd@In₂Se₃ DAC system demonstrates enhanced CO₂ activation compared to single-atom counterparts, which is attributed to the complementary roles of Nb and Pd sites. Specifically, Nb atoms primarily drive carbon reduction, while neighboring Pd atoms facilitate oxygen species removal through proton-coupled electron transfer. This dual-site interaction lowers the overall reaction barrier, promoting efficient CO₂ conversion. Notably, the polarization switching of the In₂Se₃ substrate dynamically modulates energy barriers and reaction pathways, thereby influencing product selectivity. Our work provides theoretical guidance for designing ferroelectric-supported DACs for the eCO₂RR. Full article

A series of Pd/g-C₃N₄ catalysts were synthesized using different graphitic carbon nitride precursors, and were found to exhibit significant variations in catalytic performance for solvent-free selective catalytic oxidation of benzyl alcohol. Through comprehensive characterization (XRD, N₂-BET, ICP-AES, TEM, and XPS), the experimental results found that the nitrogen chemical configuration and surface Pd²⁺concentration critically determined the catalytic efficiency. Among the various nitrogen species, N-(C)₃-type nitrogen demonstrated the strongest influence on catalytic activity, which was positively correlated with its abundance in g-C₃N₄ matrices. In particular, g-C₃N₄ derived from dicyandiamide contained the highest N-(C)₃ type nitrogen content. When serving as Pd nanoparticle support, this material simultaneously achieved the best Pd²⁺ surface concentration and catalytic performance compared to the other g-C₃N₄-supported catalysts. Full article

Carbon monoxide (CO) is an important air pollutant generated from the incomplete combustion of fossil fuels, particularly in industrial processes such as iron and steel smelting, power generation, and waste incineration, posing environmental challenges that demand effective removal strategies. Recent advances in noble metal catalysts for catalytic oxidation of CO, particularly Pt-, Pd-, and Rh-based systems, have been extensively studied. However, there is still a lack of systematic review on noble metal-based catalytic oxidation of CO, especially regarding the effects of different active components of the catalysts and the mechanism of sulfur resistance. Based on extensive research and literature findings, this study comprehensively concluded the advances in noble metal-based catalytic oxidation of CO. The effects of preparation methods, supports, and physicochemical properties on the catalytic performance of CO were explored. In addition, the mechanism of the catalytic oxidation of CO were further summarized. Furthermore, given the prevalence of SO₂ in the flue gas, the mechanism of sulfur poisoning deactivation of catalysts and the anti-sulfur strategies were further reviewed. Exploration of new supporting materials, catalyst surface reconstruction, doping modification, and other catalyst design strategies demonstrate potential in improving sulfur resistance and catalytic efficiency. This study provides valuable insights into the design and optimization of noble metal-based catalysts for the catalytic oxidation of CO. Full article

The formation of (R)-methyl-(2-hydroxy-1-phenylethyl)carbamate through Pd(PPh₃)₄-catalyzed synthesis was investigated using computational methods to elucidate the reaction pathway and energetic feasibility. Density functional theory (DFT) calculations confirmed that the direct reaction between (R)-(-)-2-phenylglycinol and methyl chloroformate is not spontaneous, requiring a catalyst to proceed efficiently. The study proposes a detailed mechanistic pathway involving ligand dissociation, intermediate formation, and hydrogenation. The role of Pd(PPh₃)₄ was examined, demonstrating its ability to stabilize reaction intermediates and facilitate key transformations, such as dehydrogenation and chlorine elimination. Two reaction pathways were identified, with Pathway 1 exhibiting a net energy of –84.7 kcal/mol and Pathway 2 showing an initial positive energy of 90.1 kcal/mol. However, the regeneration of key intermediates in Pathway 2 ultimately reduces the total reaction energy to –238.7 kcal/mol, confirming the feasibility of both routes. Computational results align with experimental NMR data, supporting the formation of the proposed intermediates. These findings provide valuable insights into catalyst optimization, suggesting that ligand modifications or alternative palladium-based catalysts could enhance efficiency. This study advances the understanding of Pd-catalyzed carbamate synthesis and offers a basis for future experimental and computational investigations. Full article

Anion exchange membrane fuel cells (AEMFCs) are versatile power generation devices that can be fed by both gaseous (H₂) and liquid fuels. The development of sustainable, efficient, and stable catalysts for the oxidation of hydrogen (HOR) and oxygen reduction (ORR) under alkaline conditions remains a challenge currently facing AEMFC technology. Reducing the loading of PGMs is essential for reducing the overall cost of AEMFCs. One strategy involves exploiting the synergistic effects of two metals in bimetallic nanoparticles (NPs). Here, we report that the activity for the HOR and the ORR can be finely tuned through surface engineering of carbon-supported PdAu-PVA NPs. The activity for both ORR and HOR can be adjusted by subjecting the material to heat treatment. Specifically, heat treatment at 500 °C under an inert atmosphere increases the crystallinity and oxophilicity of the nanoparticles, thereby enhancing anodic HOR performance. On the contrary, heat treatment significantly lowers ORR activity, highlighting how reduced surface oxophilicity plays a major role in increasing active sites for ORR. The tailored activity in these catalysts translates into high power densities when employed in AEMFCs (up to 1.1 W cm⁻²). Full article

Formic acid has recently been considered one of the most promising liquid organic hydrogen carriers (LOHCs). Its decomposition to obtain H₂ has been fruitfully investigated during recent years using catalysts of a very diverse nature. Most of these catalysts lack stability, so finding stable materials under reaction conditions is highly desirable but challenging. In the present study, catalysts based on Pd nanoparticles supported on C₃N₄-modified activated carbon derived from biomass residues were developed, characterized, and assessed in the decomposition of formic acid in the liquid phase. These catalysts were prepared using a straightforward method that allowed different nitrogen contents to be achieved in the support and avoided the ex situ reduction in the Pd precursor. The results of the catalytic tests indicated the positive role of incorporating C₃N₄, leading to catalysts that displayed much better performance than the C₃N₄-free counterpart. The incorporation of C₃N₄ resulted in catalysts with small and well-distributed Pd nanoparticles, leaching resistance and modified electronic properties of the Pd species. As a result, promising catalytic activity was observed in the developed materials. Pd/AC_C₃N₄(19) attained an initial TOF of 2893 h⁻¹, and it preserved most of its catalytic activity for at least six consecutive reaction cycles, which is a remarkable characteristic of the developed catalytic system. Full article

The oxidation of 1,2-propanediol (1,2-PDO) under alkaline heterogeneous catalysis can be optimized to produce lactic acid, a valuable commodity chemical. In this study, Pd nanoparticles supported on various metal oxides (CeO₂, CuO, ZrO₂, ZnO, SnO₂) were synthesized via a wet-chemistry method. Furthermore, CeO₂-supported Pd nanoparticle catalysts were prepared using different reduction methods. The catalytic performance for the selective oxidation of 1,2-PDO was evaluated using a range of characterization techniques. Under optimal conditions (120 °C, 1.0 MPa O₂ pressure, 2 h reaction time, and a NaOH/1,2-PDO molar ratio of 3.0), a high lactic acid yield of 62.7% was achieved. Single-factor experiments revealed that lactic acid selectivity decreased with prolonged reaction time. Conversely, increasing temperature, NaOH concentration, and O₂ pressure initially enhanced lactic acid selectivity, but further increases resulted in a decline. Physicochemical characterization revealed that different supports and reduction methods affect the basicity of the catalyst, which subsequently influences the selectivity of the target product, lactic acid. Full article

As the energy crisis and environmental pollution continue to intensify, the demand for clean energy has increased. Using two-dimensional materials to catalyze overall water splitting is an important pathway for clean energy production. This study investigated the catalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) of tri-atomic clusters supported on a two-dimensional material, graphenylene (GPN). The structural stability of GPN was thoroughly investigated, and materials were employed as substrates to support a series of 28 distinct trimer clusters composed of 3d, 4d, and 5d transition metals. Ideal combinations of these systems were screened and designed. The loading configurations of TM₃@GPN in two different systems were systematically studied. The stability of the catalyst was assessed by calculating the binding and cohesive energies and by performing molecular dynamics simulations, to confirm the catalyst stability. The optimal bifunctional catalysts for overall water splitting were identified as Au₃@GPN, Pt₃@GPN, and Pd₃@GPN, all of which demonstrated superior overall water splitting performance. As a novel two-dimensional material, biphenylene-based materials, when used to support metal clusters as bifunctional catalysts for water splitting, represent an efficient and innovative approach. Full article