Enhancement Of Catalytic Performance Research Articles

Cover Feature: High Performing and Stable Cu/NiAlOx Catalysts for the Continuous Catalytic Conversion of Ethanol into Butanol (ChemCatChem 17/2022)

The Cover Feature shows high-performing and stable Cu/NiAlOx catalysts derived from NiAl-hydrotalcite for continuous catalytic conversion of ethanol into butanol, which is one of the pivotal processes in biorefinery for the production of renewable fuels and value-added chemicals. In their Research Article, Y. Tan, W. Luo, Y.-J. Ding and co-workers report that significant enhancement in catalytic performance in terms of activity, selectivity and stability, can be attained by adding Cu properly into the NiAl-hydrotalcite. An optimal compromise between the ethanol conversion and butanol selectivity can be sustained over the optimal Cu/NiAlOx catalyst for 1000 h during the long-term stability test under moderate reaction condition, reflecting one of the state-of-the-art performances for non-noble metal-based heterogeneous catalysts in this Guerbet coupling process. More information can be found in the Research Article by Y. Tan, W. Luo, Y.-J. Ding and co-workers.

Interfacial-interaction-induced fabrication of biomass-derived porous carbon with enhanced intrinsic active sites

Carbon catalysis is an attractive metal-free catalytic transformation, and its performance is significantly dependent on the number of accessible active sites. However, owing to the inherent stability of the C–C linkage, only limited active sites at the edge defects of the basal plane can be obtained even after a harsh oxidation treatment. In this study, the concept of interfacial interactions was adopted to propose an efficient strategy to develop highly active carbon catalysts. The alumina/carbon interface formed in situ acted as a cradle for the generation of oxygen-containing functional groups. In the absence of oxidation treatment, the concentration of oxygen-containing functional groups and the specific surface area can reach 1.27 mmol·g−1 and 2340 m2·g−1, respectively, which are significantly higher than those of carbon prepared by traditional hard template methods. This active carbon shows a significant enhancement in catalytic performance in the oxidative coupling of amine to imine, about 22-fold higher than that of a well-known graphite oxide catalyst. Such interfacial interaction strategies are based on sustainable carbon sources and can effectively tune the porous structure of carbon in the micro- and meso-ranges. This conceptual finding offers new opportunities for the development of high-performance carbon-based metal-free catalysts.

Boosting CO2 hydrogenation efficiency for methanol synthesis over Pd/In2O3/ZrO2 catalysts by crystalline phase effect

The crystalline phases of support have great influence on their surface and structure properties. Therefore, adjusting the crystalline structure of heterogeneous catalysts imposes a significant impact on the catalytic performance. Herein, a suite of Pd/In2O3/ZrO2 catalysts with different crystalline phases of ZrO2 were prepared and evaluated for CO2 hydrogenation to CH3OH using the same amount of metal loading. The activity data showed the distinct superior reactivity of Pd/In2O3/ZrO2 catalyst used mixed monoclinic and tetragonal phases ZrO2(Mix-ZrO2) as support as compared to respective single phase of monoclinic ZrO2(m-ZrO2) and tetragonal ZrO2(t-ZrO2). The catalysts are extensively characterized through BET, XRD, HRTEM, UV–vis, H2-TPR, CO2/H2-TPD and XPS. Combining the characterization results and activity data, the superior activity of Pd/In2O3/Mix-ZrO2 catalyst can be correlated with large particle size of Pd nanoparticles, the concentration of oxygen vacancies, and the abundant medium basic sites, which were essential for activation of H2 and inert CO2 and enhancement of catalytic performance. The best-performing Pd/In2O3/Mix-ZrO2 catalyst exhibited a remarkable reactivity with space time yield (STY) of 0.54 gmethanol·h−1·gcat−1 at 573 K and 5 MPa, and stability without noticeable deactivation after 100 h of time on stream, demonstrating its potential as catalyst used in CH3OH synthesis from CO2 hydrogenation.

Methanol Oxidation Catalytic Performance Enhancement via Constructing Pd-MgAl2O4 Interface and its Reaction Mechanism Investigation

Methanol Oxidation Catalytic Performance Enhancement via Constructing Pd-MgAl2O4 Interface and its Reaction Mechanism Investigation

Enhancement of catalytic performance of cobalt-doped g-C3N4 catalyst by the synergistic interaction between photocatalytic and peroxymonosulfate activation system

Enhancement of catalytic performance of cobalt-doped g-C3N4 catalyst by the synergistic interaction between photocatalytic and peroxymonosulfate activation system

Tailoring Binding Abilities By Incorporating Oxophilic Transition Metals on 3D Nanostructured Ni Arrays for Accelerated Alkaline Hydrogen Evolution Reaction

Developing efficient and inexpensive electrocatalysts for the hydrogen evolution reaction (HER) in alkaline water electrolysis plays a key role for renewable hydrogen energy technology. The slow reaction kinetics of HER in alkaline solutions, however, has hampered advances in high-performance hydrogen production. Herein, we investigated the trends in HER activity with respect to the binding energies of Ni-based thin film catalysts by incorporating a series of oxophilic transition metal atoms. It was found that the doping of oxophilic atoms enables the modulation of binding abilities of hydrogen and hydroxyl ions on the Ni surfaces, leading to the first establishment of a volcano relation between OH-binding energies and alkaline HER activities. In particular, Cr-incorporated Ni catalyst shows optimized OH-binding as well as H-binding energies for facilitating water dissociation and improving HER activity in alkaline media. Further enhancement of catalytic performance was achieved by introducing an array of three-dimensional (3D) Ni nanohelixes (NHs) that provide abundant surface active sites and effective channels for charge transfer and mass transport. The Cr dopants incorporated into the Ni NHs accelerate the dissociative adsorption process of water, resulting in remarkably enhanced catalytic activities in alkaline medium. Our approach can provide a rational design strategy and experimental methodology toward efficient bimetallic electrocatalysts for alkaline HER using earth-abundant elements.

Simultaneously Enhancing Catalytic Performance and Increasing Density of Bifunctional CuN3 Active Sites in Dopant-Free 2D C3N3Cu for Oxygen Reduction/Evolution Reactions.

Atomically dispersed M–N–C has been considered an effective catalyst for various electrochemical reactions such as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which faces the challenge of increasing metal load while simultaneously maintaining catalytic performance. Herein, we put forward a strategy for boosting catalytic performances of a single Cu atom coordinated with three N atoms (CuN3) for both ORR and OER by increasing the density of connected CuN3 moieties. Our calculations first show that a single CuN3 moiety exhibiting no catalytic performance for ORR and OER can be activated by increasing the density of metal centers, which weakens the binding affinity to *OH due to the lowered d-band center of the metal atoms. These findings stimulate the further theoretical design of a two-dimensional compound of C3N3Cu with a high concentration of homogeneously distributed CuN3 moieties serving as bifunctional active sites, which demonstrates efficient catalytic performance for both ORR and OER as reflected by the overpotentials of 0.71 and 0.43 V, respectively. This work opens a new avenue for designing effective single-atom catalysts with potential applications as energy storage and conversion devices possessing high density of metal centers independent of the doping strategy and defect engineering, which deserves experimental investigation in the future.

CuCo2S4@B,N-Doped Reduced Graphene Oxide Hybrid as a Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions.

In this report, a facile synthetic route is adopted for typically designing a hybrid electrocatalyst containing boron, nitrogen dual-doped reduced graphene oxide (B,N-rGO) and thiospinel CuCo2S4 (CuCo2S4@B,N-rGO). The electrocatalytic activity of the hybrid catalyst is tested with respect to oxygen evolution (OER) and oxygen reduction (ORR) reactions in alkali. Physicochemical characterizations confirm the unique formation of a reduced graphene oxide–non-noble-metal sulfide hybrid. Electrochemical evaluation by cyclic voltammetry (CV) and linear-sweep voltammetry (LSV) reveals that the CuCo2S4@B,N-rGO hybrid possesses enhanced ORR and OER activity compared to the B,N-rGO-free CuCo2S4 catalyst. The synthesized CuCo2S4@B,N-rGO hybrid demonstrates remarkable enhancement in catalytic performance with an improved onset potential (1.50 and 0.88 V) and low Tafel slope (112 and 73 mV dec–1) for both OER and ORR processes, respectively. In addition, the catalyst exhibits a diminutive potential difference (0.81 V) between the potential corresponding to the 10 mA cm–2 current density for OER and the half-wave potential for ORR. The superior catalytic activity and high durability of the hybrid material may be attributed to the synergistic effect arising from the metal sulfide and dual-doped reduced graphene oxide. The present study illuminates the possibility of using the dual-doped graphene oxide and metal sulfide hybrid as a competent bifunctional cathode catalyst for renewable energy application.

Unity Makes Strength: Constructing Polymeric Catalyst for Selective Synthesis of CO 2 /Epoxide Copolymer

Unity Makes Strength: Constructing Polymeric Catalyst for Selective Synthesis of CO ₂ /Epoxide Copolymer

Transition Metal Atoms Anchored on CuPS3 Monolayer for Enhancing Catalytic Performance of Hydrogen Evolution Reactions

The noble metal such as Pt has been used as the catalysts for hydrogen evolution reaction (HER), but with problems such as scarcity of resources and high cost. Anchoring transition metal atoms onto the catalysts is regarded as a potential approach to solve this problem and enhance the electrocatalytic performance of HER. For this purpose, two-dimensional materials, such as CuPS3 monolayer, are regarded as one of the most ideal carriers for adsorption of metal atoms. However, there is no previous study on this topic. In this paper, we systematically studied microstructures, electronic properties, and electrocatalytic performance of the CuPS3 monolayer anchored with transition metal atoms (e.g., Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) using a density functional theory (DFT). Results showed that all the transition metal atoms are favorably adsorbed onto the CuPS3 monolayer with large binding energies at the top of the Cu atom. The pristine CuPS3 monolayer has a large catalytic inertia for hydrogen evolution reactions, whereas after anchored with transition metal atoms, their catalytic performances have been significantly improved. The Gibbs free energy (ΔGH) is 0.44 eV for the H atom absorbed onto the pristine CuPS3 monolayer, whereas the ΔGH values for the V, Fe, and Ni atoms anchored onto the CuPS3 monolayer are 0.02, 0.11, and 0.09 eV, respectively, which is close to the ΔGH of H atom adsorbed on Pt (e.g., −0.09 eV). At the same time, the influence of hydrogen coverage rate was calculated. The result shows that V adsorbed on CuPS3 monolayer is catalytic active for HER for a large range of hydrogen coverage. Our results demonstrate that anchoring of V atom onto the CuPS3 monolayer is a potentially superior method for making the catalyst for the HER.Graphical abstract

Efficient activation of peroxymonosulfate mediated by Co(II)-CeO2 as a novel heterogeneous catalyst for the degradation of refractory organic contaminants: Degradation pathway, mechanism and toxicity assessment

A series of Co(II)-CeO2 mixed metal oxides were synthesized by a facile hydrothermal-calcination procedure for activating peroxymonosulfate (PMS) and degrading toxic and difficult biodegradable organics. Co(II)-CeO2 showed excellent degradation performance toward rhodamine B (RhB), toluidine blue, methylene blue and diclofenac. RhB is a refractory organic contaminant, and ecotoxicological evaluation unraveled its harmfulness to the biosphere. RhB was selected as the model pollutant to investigate catalytic mechanisms. Parameters affecting degradation performance were profoundly investigated, including Co:Ce feed ratio, initial pH, PMS dosage, catalyst dosage, RhB concentration, coexisting ions and reaction temperature. Reaction mechanisms were proposed based on density functional theory calculations and identifications of reactive oxygen species. Improvements have been achieved in seven aspects compared to previous studies, including 100% degradation ratio in both real water samples and each reuse of the catalyst, ultrafast degradation rate, cost-effectiveness of the catalyst, toxicity-attenuation provided by the developed degradation method, high degree of mineralization for the model pollutant, negligible leaching of active sites, and the enhancement of catalytic performance by utilizing trace leached cobalt, endowing the technique with broad applicability and prospect.

Synthesis, structural and optical properties of phosphorus doped MnO2 nanorods as an under sunlight illumination with intensify photocatalytic for the degradation of organic dyes

Based on the contributions of Phosphorus and its compound species are great advances in photocatalytic degradation performance. In this article, pure and P doped MnO2 nanoparticles were synthesized by the hydrothermal method. The evenly distributed Phosphorus has good contact with MnO2. The findings of the XRD diffraction validated the synthesis of a well-defined tetragonal phase of pure and P doped MnO2. The bonding of functional groups Phosphorus band is strongly related to the Phosphorus-oxy compound (P-O-C) confirmed by Fourier transform infrared spectroscopy (FTIR) analysis. Morphology of pure and P doped MnO2 was studied using scanning electron microscopy (SEM) and Field emission scanning electron microscopy (FESEM). The existences of all component atoms in the crystal structure of all samples are verified using energy-dispersive X-ray spectroscopy (EDX).UV–visible diffuse reflectance spectroscopy (UV-Vis DRS) was used to characterize bandgap values. The bandgap values of pure and 2%, 4%, 6% of P doped MnO2 are 2.61 eV and 2.19 eV, 2.10 eV, 1.90 eV, respectively. They confirmed the bandgap values decreases by increasing the percentage of P dopant. The photocatalytic performance of all pure and P doped MnO2 samples are investigated utilizing photodegradation of MO and RhB dyes in the sight of sunshine. Trapping experiments confirmed the dyes sensitization photodegradation is eliminated by active photodegradation, such as TEOA, Ag(NO)3, IPA, and BQ, which represents photogenerated h+, e-, ·OH, and O2- created and active during photocatalytic degradation procedure were enhanced. The photocatalytic activity of pure and P doped MnO2 nanoparticles show the degradation efficiency of MO and RhB dyes at 85% and 90%, respectively. Furthermore, P/MnO2 doping was effectively utilized for five photodegradation cycles without a significant change in activity, and crystalline characteristics. Moreover, the mechanism of catalytic performance enhancement also has been discussed. These nanoparticle materials are the potential candidates for high-performance photocatalytic application.

Promotion effect of alkaline leaching on the catalytic performance over Cu/Fe-SSZ-13 catalyst for selective catalytic reduction of NOx with NH3

BackgroundCu-SSZ-13 is used to catalytic reduce the diesel NOx emissions, but its catalytic performance (catalytic activity, stability and sulfur resistance) is unsatisfactory in commercial application. So a novel strategy was desired to promote the catalytic ability. MethodsThe raw zeolite H-SSZ-13 was firstly treated using NaOH, followed by loading Fe via impregnation and Cu modifying using ion-exchange, respectively. The influence mechanism of base leaching on structure and catalytic performance was evaluated by several characterization techniques. Significant findingsThe base leaching can effectively promote the catalytic performance of Cu/Fe-SSZ-13. When the adopted NaOH concentration is 0.1 M, the as-synthesized catalyst exhibits superior catalytic activity, robust hydrothermal stability and good sulfur resistance compared with the commercial Cu-SSZ-13. The characterization results revealed that fine control of the base leaching could significantly promote the interaction between active metals and zeolite framework, induce the formation of Lewis acid sites, improve redox ability, effectively promote the generation of Cu2+-2Z. It also significantly accelerated the reaction rate of adsorbed NOx species with NH3 via promoting the generation of NO2 and NH3 activation, all of which were consequently responsible for the enhancement of catalytic performance. The NH3-SCR reaction over Cu/Fe-SSZ-13 followed a possible L-H mechanism.

Built-in electric field mediated peroxymonosulfate activation over biochar supported-Co3O4 catalyst for tetracycline hydrochloride degradation

The strong electronic interaction between heterogeneous composite catalysts facilitates the charge separation and transfer, which is favorable for the enhancement of catalytic performance. Herein, the rape straw derived biochar (BC) supported ultrafine Co3O4 composites were synthesized for tetracycline hydrochloride (TC) degradation via activating peroxymonosulfate (PMS), and the built-in electric field (BIEF) driven catalytic degradation mechanism was proposed. The results indicated that 20 wt% Co3O4/BC catalyst could achieve 90% degradation efficiency of TC within 20 min, and demonstrated that BC not only served as a support to significantly inhibit the agglomeration of Co3O4 nanoparticles and improve the stability of catalyst, but also behaved as an activator of PMS to participate in the catalytic degradation reaction. Both radical pathway (SO4·-, ·OH and O2·-) and non-radical process (1O2 and direct electron transfer) were involved in the Co3O4/BC/PMS system, and the role of the latter is more prominent, in which Co2+/Co3+ redox cycle and C = O groups on the BC were the possible active sites. Furthermore, the density functional theory (DFT) calculations revealed that a BIEF pointing from BC to Co3O4 at the interface was formed, which could act as the internal driving force for electron transfer to accelerate the redox cycle of Co2+/Co3+ and induce the direct electron transfer, and thus resulting in the better degradation of TC. This work not only offered a mechanistic insight into synergistic effects of composite catalyst in PMS activation, but also provided a win–win strategy of realizing the resource utilization of agricultural waste and environmental remediation simultaneously.

Enhancing catalytic performance of Ag-CeO2 catalysts for catalytic CO combustion: Ag-CeO2 interface interaction and Na-promoting action

Ag-CeO2 catalysts were prepared via urea- and activated carbon- assisted pyrolysis to study an improvement strategy for their catalytic performance in catalytic CO combustion. Different synthetic methods induced the change of Ag-CeO2 interface interaction by tuning the surface chemical state of Ag nanoparticles and CeO2 nanoparticles. However, it was completely different to arouse the change degree in the structure and performance of these Ag-CeO2 catalysts. Fabrication of Ag-CeO2 catalysts using a urea pyrolysis induced to create an Ag-CeO2 interface with more metallic Ag species, which improved the reductivity of CeO2 surface and enhanced the Ag-CeO2 catalyst performance. Fabrication of Ag-CeO2 catalysts using an activated carbon pyrolysis method induced to form an Ag-CeO2 interface with more positively charged Ag+ ions and required higher temperature of CO conversion. For the Ag-CeO2 catalysts with more positively charged Ag+ species, the participation of sodium salts could alleviate Ag nanoparticle oxidation and promoted the transformation of Ag-CeO2 interface with more positively charged Ag+ ions into Ag-CeO2 interface with more metallic Ag species, which caused the formation of more Ce3+ cations and the production of more reducible surface oxygen and enhanced the catalyst performance in catalytic CO combustion.

Confined heterogeneous catalysis by boron nitride-Co3O4 nanosheet cluster for peroxymonosulfate oxidation toward ranitidine removal

Peroxymonosulfate (PMS) induced advanced oxidation processes hold great promise for heterogeneous oxidation reactions. In this study, boron nitride (BN)-Co3O4 nanosheet cluster (NC) was fabricated to facilitate PMS activation with a nanoconfined heterogeneous catalysis effect for the rapid removal of ranitidine (RAN) under mild conditions. The obtained BN-Co3O4 NC cluster exhibited efficient catalysis performance with a 99.5% removal efficiency for ranitidine in 5 min, and meanwhile this novel catalyst could be applied under a wide pH range (pH: 3–9) with still high degradation efficiencies. The porous structure of BN-Co3O4 NC provided a large number of channels for RAN and PMS molecules to enter the catalyst’s inner confinement space, resulting in a remarkable enhancement of catalytic performance. The kinetic rate constant for RAN degradation by the BN-Co3O4 NC/PMS system with 3–33 fold less catalyst dosage is much larger (1.58–213 fold) compared with the state-of-the-art. PMS activation by BN-Co3O4 NC was mainly due to the pathway of reduction via active radicals. Density functional theory calculations specified that the concomitant active radicals such as ∙OH and SO4∙− were mainly derived from PMS activation via O-O bond cleavage. This work provides a new perspective for regulating the structure of Co3O4 and elucidating the mechanism of PMS-induced heterogeneous catalytic oxidation.

Porphyrins and phthalocyanines as biomimetic tools for photocatalytic H2 production and CO2 reduction.

The increasing energy demand and environmental issues caused by the over-exploitation of fossil fuels render the need for renewable, clean, and environmentally benign energy sources unquestionably urgent. The zero-emission energy carrier, H2 is an ideal alternative to carbon-based fuels especially when it is generated photocatalytically from water. Additionally, the photocatalytic conversion of CO2 into chemical fuels can reduce the CO2 emissions and have a positive environmental and economic impact. Inspired by natural photosynthesis, plenty of artificial photocatalytic schemes based on porphyrinoids have been investigated. This review covers the recent advances in photocatalytic H2 production and CO2 reduction systems containing porphyrin or phthalocyanine derivatives. The unique properties of porphyrinoids enable their utilization both as chromophores and as catalysts. The homogeneous photocatalytic systems are initially described, presenting the various approaches for the improvement of photosensitizing activity and the enhancement of catalytic performance at the molecular level. On the other hand, for the development of the heterogeneous systems, numerous methods were employed such as self-assembled supramolecular porphyrinoid nanostructures, construction of organic frameworks, combination with 2D materials and adsorption onto semiconductors. The dye sensitization on semiconductors opened the way for molecular-based dye-sensitized photoelectrochemical cells (DSPECs) devices based on porphyrins and phthalocyanines. The research in photocatalytic systems as discussed herein remains challenging since there are still many limitations making them unfeasible to be used at a large scale application before finding a large-scale application.

Enhancement in catalytic performance of birnessite-type MnO2-supported Pd nanoparticles by the promotional role of reduced graphene oxide for toluene oxidation

We designed and prepared δ-MnO2-supported reduced graphene oxide-promoted Pd nanoparticles (xPd–yrGO/δ-MnO2). Such a catalytic material is promising in the practical application for VOCs removal.

Increased crystallinity of RuSe2/carbon nanotubes for enhanced electrochemical hydrogen generation performance.

Ru-Based catalysts are significant in the green hydrogen generation via the electrochemical water-splitting reaction. Herein, it is found that the increased crystallinity of cubic RuSe2 nanoparticles anchored over carbon nanotubes (RuSe2/CNTs) could largely increase the hydrogen generation performance both in acidic and alkaline electrolytes. The freshly prepared RuSe2/CNTs with low crystallinity had a very low catalytic performance for the HER, while the catalytic ability could be largely boosted by facile thermal annealing at 650 °C in an N2 atmosphere, resulting from the increased crystallinity and electronic effect. The crystal structure enhancement of the RuSe2 nanoparticles was well supported by the X-ray diffraction technique and the lattice fringes in the high-resolution transmission electron microscopy images. As a result, the catalyst exhibited largely improved catalytic performance compared to the freshly prepared RuSe2/CNTs; specifically, the overpotentials of 48 and 64 mV were required to drive 10 mA cm-2 in alkaline and acidic media when loaded on a glassy carbon electrode, much less than those of 109 and 120 mV for the freshly prepared RuSe2/CNTs; the catalytic performance in the alkaline electrolyte was even close to that of the commercial Pt/C catalyst. Correspondingly, the improved catalytic stability, catalytic kinetics, charge transfer ability and catalytic efficiency of the active sites were also observed. The current work shows an effective approach and important understanding for catalytic performance enhancement via increased crystallinity by facile thermal annealing.

Enhancing catalytic performance of AuPd catalysts towards the direct synthesis of H2O2 through incorporation of base metals

The introduction of small quantities of tertiary base metals into supported AuPd nanoparticles is found to result in improved catalytic performance towards the direct synthesis of H2O2 compared to the bi-metallic analogue.