Showing papers on "Catalyst support published in 2021"

Phase tuning of ZrO2 supported cobalt catalysts for hydrodeoxygenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran under mild conditions

Abstract: Crystal structure of catalyst support has great influence on its surface and electronic properties. Thus, tuning the crystal phase may adjust the catalytic activity. Herein, we prepared a series of monoclinic, tetragonal and mixed phase of Co/ZrO2 catalysts, denoted as Co/m-ZrO2, Co/t-ZrO2 and Co/Mix-ZrO2. They showed different hydrogenation and hydrogenolysis activities in conversion of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF). The characterization and catalytic performance indicated that the interaction between cobalt and t-ZrO2 resulted in cobalt electron-deficiency and higher concentration of Zr(III) species, which contributed to the higher hydrogenation activity of carbonyl on Co/t-ZrO2 than Co/m-ZrO2. While the hydrogenolysis of C OH group showed higher efficiency on Co/m-ZrO2, which was determined by the acid concentration on the surface of catalysts. The combination of both high hydrogenation and hydrogenolysis activities in Co/Mix-ZrO2 achieved the highest yield of DMF (90.7 %) under mild conditions of 130 °C and 1 MPa H2.

Engineering catalyst supports to stabilize PdOx two-dimensional rafts for water-tolerant methane oxidation

Abstract: The treatment of emissions from natural gas engines is an important area of research since methane is a potent greenhouse gas. The benchmark catalysts, based on Pd, still face challenges such as water poisoning and long-term stability. Here we report an approach for catalyst synthesis that relies on the trapping of metal single atoms on the support surface, in thermally stable form, to modify the nature of further deposited metal/metal oxide. By anchoring Pt ions on a catalyst support we can tailor the morphology of the deposited phase. In particular, two-dimensional (2D) rafts of PdOx are formed, resulting in higher reaction rates and improved water tolerance during methane oxidation. The results show that modifying the support by trapping single atoms could provide an important addition to the toolkit of catalyst designers for controlling the nucleation and growth of metal and metal oxide clusters in heterogeneous catalysts. Despite its importance in the context of natural gas engines emissions treatment, methane oxidation remains challenging. Now, the authors introduce an approach to stabilize PdOx rafts on ceria by trapping Pt single atoms in the support resulting in a superior catalyst for this transformation.

A Brief Overview of Recent Progress in Porous Silica as Catalyst Supports

Abstract: Porous silica particles have shown applications in various technological fields including their use as catalyst supports in heterogeneous catalysis. The mesoporous silica particles have ordered porosity, high surface area, and good chemical stability. These interesting structural or textural properties make porous silica an attractive material for use as catalyst supports in various heterogeneous catalysis reactions. The colloidal nature of the porous silica particles is highly useful in catalytic applications as it guarantees better mass transfer properties and uniform distribution of the various metal or metal oxide nanocatalysts in solution. The catalysts show high activity, low degree of metal leaching, and ease in recycling when supported or immobilized on porous silica-based materials. In this overview, we have pointed out the importance of porous silica as catalyst supports. A variety of chemical reactions catalyzed by different catalysts loaded or embedded in porous silica supports are studied. The latest reports from the literature about the use of porous silica-based materials as catalyst supports are listed and analyzed. The new and continued trends are discussed with examples.

Cobalt catalysts on carbon-based materials for Fischer-Tropsch synthesis: a review

Abstract: This review analyzes the literature from the 80’s to the beginning of 2020 and covers the use of carbon materials as supports for cobalt-based catalysts used in the Fischer Tropsch reaction. The article is composed of two sections. The first one details the reactivity of carbon supported cobalt catalysts with a particular focus on: i) reaction mechanisms and conditions, ii) effect of cobalt particle size, iii) confinement effects, iv) hydrogen spillover, and v) deactivation mechanisms. In the second part, the different methods of Co/C catalyst preparation are presented, and the influence of several parameters such as the type of supports and its functionalization, the metal loading or the catalyst activation on the catalytic performances is discussed. This work also provides some perspectives in the field.

Bimetal–Organic Frameworks from In Situ-Activated NiFe Foam for Highly Efficient Water Splitting

Abstract: Nickel–iron foam (NFF) has high air permeability and a high specific surface area because of its connected pore structure and high porosity, making it an ideal catalyst support material. However, it is challenging to effectively utilize metal ions in the NFF to prepare new advanced electrocatalysts without introduction of metal species. Here, we demonstrate that activated metal ions in NiFe foam serve as the support and metal sources for in situ synthesis of NiFe bimetal–organic frameworks (NFF-MOF). Specifically, by further acidification to activate NiFe metal ions on the NFF backbone, and then to generate active NFF-MOF species through the participation of the organic ligand, the resulting NFF-MOF material exhibits significantly improved electrocatalytic performance toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with ultralow overpotentials of 81 and 250 mV at a current density of 10 mA cm–2, respectively. Density functional theory calculations and experimental results suggest that the NFF-MOF from the in situ-activated NiFe foam promotes transport and separation of charge because of highly uniform dispersed metal sites, high porosity, and an ordered 3D skeleton structure, thus accelerating the electrochemical HER and OER. This work brings new insights for the development of next-generation high-efficiency electrocatalysts.

Effect of Pt and Ionomer Distribution on Polymer Electrolyte Fuel Cell Performance and Durability

Abstract: Carbon black (CB), which has been widely used as a catalyst support, has been treated by various activation processes in order to increase the surface area. High-surface-area CB has a high pore vol...

Strong catalyst support interactions in defect-rich γ-Mo2N nanoparticles loaded 2D-h-BN hybrid for highly selective nitrogen reduction reaction

Abstract: Electrochemical ammonia synthesis by N2 fixation has proven to be a promising alternative to the energy-consuming, befouling Haber-Bosch process. Considering the low faradaic efficiency and sluggish kinetics of Nitrogen Reduction Reaction (NRR), it is significant to design a robust and selective catalyst. Herein, we demonstrate a single step in-situ nitridation method to grow cubic molybdenum nitride (γ-Mo2N) nanoparticles on a 2D hexagonal boron nitride (h-BN) sheets as a potential, cost-effective electrocatalyst for NRR, in which the selectivity for N2 was regulated by interfacially engineering the Mo2N-BN bridge. The maneuverability of h-BN sheets enabled the provocation of N-vacancies governed by the particle size, where the fine-tuning of their significance emanated the highest faradaic efficiency of 61.5 %. Moreover, such non-noble metal-based hybrids delivered a stable performance for 20 h. Therefore, our approach of designing the electronic structure of a catalyst by controlling the defects could be an effective practice for selective NRR.

Catalytic oxidation of CO on noble metal-based catalysts

Abstract: Carbon monoxide (CO) catalytic oxidation has gained increasing interest in recent years due to its application prospects. The noble metal catalysts commonly exhibit outstanding CO catalytic oxidation activity. Therefore, this article reviewed the recent research on the application of noble metal catalysts in the catalytic oxidation of CO. The effects of catalyst support, dopant, and physicochemical properties on the catalytic activity for CO oxidation are summarized. The influence of the presence of water vapor and sulfur dioxide in the reaction atmosphere on the catalytic activity in CO oxidation is emphatically discussed. Moreover, this paper discussed several reaction mechanisms of CO catalytic oxidation on noble metal catalysts. Finally, the challenges of removing CO by catalytic oxidation in practical industrial flue gas are proposed.

Highly active and stable Ni/perovskite catalysts in steam methane reforming for hydrogen production

Abstract: Perovskites are good candidates as a catalyst support to enhance the catalytic performance of Ni catalysts in steam methane reforming for hydrogen production. To obtain a Ni/perovskite catalyst with a high activity and stability, different LaBO3 (B = Al, Fe, Mn), La0.7A0.3AlO3−δ (A = Ca, Ba, Ce, Zn, Sr, Mg) and La1−xMgxAlO3−δ perovskites were prepared and their role in supporting Ni catalysts was comprehensively investigated in the current work. Catalyst characterization methods, including XRD, H2-TPR, H2-TPD, XPS, TG and Raman spectroscopy, were also used to understand the underlying mechanisms. The results show that the doping of Ca, Ba, Ce and Zn in the A site of the perovskite lowers the catalytic activity, while the partial substitution of Mg and Sr could improve the activity of Ni/LaAlO3. More importantly, it is suggested that the Ni/La0.7Mg0.3AlO3−δ catalyst has an outstanding catalytic activity and resistance to carbon deposition, and there is some carbon deposited after a stability test lasting for 35 h. The excellent catalytic performance is determined to be due to the higher dispersion of active Ni, the greater the amount of surface oxygen, the stronger the interaction between the active metal and support due to the partial doping of Mg.

One-pot transesterification of non-edible Moringa oleifera oil over a MgO/K2CO3/HAp catalyst derived from poultry skeletal waste

Abstract: A hydroxyapatite (HAp) catalyst support from poultry’s bones was derived and then modified with MgO/K2CO3 to generate a heterogeneous catalyst to produce biodiesel from a non-edible Moringa oleifera oil. The catalyst properties were analyzed with SEM, EDX-Map, XRD, FTIR, and N 2 adsorption–desorption. A design of experiments by response surface methodology (RSM) via central composite design (CCD) including catalyst loading (1–5 wt%), temperature (40–80 °C), reaction time (50–250 min), and methanol to oil ratio (0.346–0.81 w/w) optimized the biodiesel yield. The P -value and F-value of the model proposed were 677.129 and

Contribution of B,N-co-doped reduced graphene oxide as a catalyst support to the activity of iridium oxide for oxygen evolution reaction

Abstract: The current research deals with the study of boron and nitrogen co-doped reduced graphene oxide (BN-rGO) as a support material for iridium oxide (IrO2) nanoparticles for oxygen evolution reaction (OER) catalysis. The synthetic approach for the IrO2–BN-rGO catalyst involves the combination of pyrolysis and hydrothermal methods used for hierarchical nanostructures. BN-rGO possesses B–N, B–C, and N–C functional groups to support and stabilize the IrO2 catalyst nanoparticles. The altered electronic states of IrO2 on the BN-rGO support are compared with those of IrO2 on a non-doped support, rGO (IrO2–rGO), and on commercial BN sheets (IrO2–c-BN). The catalyst shows a low overpotential (300 mV at 10 mA cm−2), high current density (55 mA cm−2 at 1.65 V), and significantly high durability (12 350 cycles; 45 h) in an acidic environment. The high stability of IrO2–BN-rGO may result from the presence of a chemically and electrochemically stable B–N bond. We confirm that other functional groups (B–C and N–C) and the rGO framework are equally crucial for better attachment of IrO2 nanoparticles.

Robust coal matrix intensifies electron/substrate interaction of nickel-nitrogen (Ni-N) active sites for efficient CO2 electroreduction at industrial current density

Abstract: Carbon encapsulating metal composites have been widely employed in electrocatalytic reduction of CO2. Though these catalysts possess relatively high selectivity towards CO, their current densities are usually low, which hardly satisfy industrial requirements. Achieving industrial current densities requires robust catalyst supports alongside efficient electron/substrate interaction at catalytically active sites. Herein, we select anthracite coal with a naturally robust architecture as the catalyst support, whose internal dense framework favours electron transport. The controllable activation method is used to form numerous micropores at the surface of coal particles without destroying the internal structures. The spatial confinement growth effect of micropores within the coal matrix contributes to the fixation of nickel-nitrogen (Ni-N) active sites within the micropores to prevent excessive agglomeration of metallic atoms, therefore enhancing the catalyst utilization. Furthermore, confinement space provided by plentiful micropores favours the adsorption of CO2, ensuring the instantaneous supply of a sufficient concentration of the substrate molecules to adjacent active sites firmly anchored in the micropores. Accordingly, the robust coal matrix can not only promote electrons from the inside to surface catalytic centres but also capture CO2 from the outside to active sites, thus intensifying the electron/substrate interaction of Ni-N active sites. In a flow cell, the coal-matrix electrocatalyst co-doped with nickel and nitrogen exhibits an industry-level current density of 223 mA cm–2, a high faradaic efficiency of 97% for CO production and a long-term stability of continuously working for as long as 120 h. Consequently, this work advances the understanding of catalyst supports in intensifying the electron/substrate interaction of active sites and hence provides new insight into the optimization of electrocatalytic performance of earth-abundant transition metals through the incorporation into the robust coal matrix.

Graphene-Like Hydrogen-Bonded Melamine–Cyanuric Acid Supramolecular Nanosheets as Pseudo-Porous Catalyst Support

Abstract: Behaving as structural protectors and electronic modulators, catalyst supports such as graphene derivatives are generally constructed by covalent bonds. Here, hydrogen-bonded ultrathin nanosheets are reported as a new type of catalyst support. Melamine (M) and cyanuric acid (CA) molecules self-assemble to form the graphite-like hydrogen-bonded co-crystal M-CA, which can be easily exfoliated by ultrasonic treatment to yield ultrathin nanosheets with thickness of ≈1.6 nm and high stability at pH = 0. The dynamic nanosheets form adaptive defects/pores in the synthetic process of CoP nanoparticles, giving embedded composite with high hydrogen evolution activity (overpotential of 66 mV at 10 mA cm-2 ) and stability. Computational calculations, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy unveil the electron modulation effects of the nanosheets. This pseudo-porous catalyst support also can be applied to other metal phosphides.