Catalyst Surface Research Articles

Halogen Tailoring of Platinum Electrocatalyst with High CO Tolerance for Methanol Oxidation Reaction.

The catalytic activity of platinum for CO oxidation depends on the interaction of electron donation and back-donation at the platinum center. Here we demonstrate that the platinum bromine nanoparticles with electron-rich properties on bromine bonded with sp-C in graphdiyne (PtBr NPs/Br-GDY), which is formed by bromine ligand and constitutes an electrocatalyst with a high CO-resistant for methanol oxidation reaction (MOR). The catalyst showed peak mass activity for MOR as high as 10.4 A mgPt -1, which is 20.8 times higher than the 20 % Pt/C. The catalyst also showed robust long-term stability with slight current density decay after 100 hours at 35 mA cm-2. Structural characterization, experimental, and theoretical studies show that the electron donation from bromine makes the surface of platinum catalysts highly electron-rich, and can strengthen the adsorption of CO as well as enhance π back-donation of Pt to weaken the C-O bond to facilitate CO electrooxidation and enhance catalytic performance during MOR. The results highlight the importance of electron-rich structure among active sites in Pt-halogen catalysts and provide detailed insights into the new mechanism of CO electrooxidation to overcome CO poisoning at the Pt center on an orbital level.

Linking Ab initio density functional theory with modelling reaction microkinetics to understand catalytic fatty acids hydro-deoxygenation intermediate species selectivity

Catalyst surfaces enable the catalytic reactions via binding of substrates and lowering the reaction barriers to obtain the desired products. Separating the binding process from the reaction barriers enables us the understanding of surface properties and enables the reaction engineering strategies such as choice of solvents or functional groups protections. Through the modelling of the hydrodeoxygenation (HDO) of fatty acids, namely Stearic, Oleic, Linoleic, Myristic and Decanoic acid we show why the alkanes are the ideal solvent choice for NiMoS catalyst, why the alcohols side products form, regardless of the kinetic constant indicating fast dehydration, why the aldehydes intermediates are rarely detected and why hydrogenation of double bonds supersedes other kinetics events. We confirm the DFT calculations by integrating them into the kinetic model which confirms that the obtained results are sensible and usable in reaction engineering. The results are supported by the detailed characterization of the NiMoS catalyst.

Concurrent Amorphization and Nanocatalyst Formation in Cu-Substituted Perovskite Oxide Surface: Effects on Oxygen Reduction Reaction at Elevated Temperatures.

The activity and durability of chemical/electrochemical catalysts are significantly influenced by their surface environments, highlighting the importance of thoroughly examining the catalyst surface. Here, Cu-substituted La0.6Sr0.4Co0.2Fe0.8O3-δ is selected, a state-of-the-art material for oxygen reduction reaction (ORR), to explore the real-time evolution of surface morphology and chemistry under a reducing atmosphere at elevated temperatures. Remarkably, in a pioneering observation, it is discovered that the perovskite surface starts to amorphize at an unusually low temperature of approximately 100 °C and multicomponent metal nanocatalysts additionally form on the amorphous surface as the temperature raises to 400 °C. Moreover, this investigation into the stability of the resulting amorphous layer under oxidizing conditions reveals that the amorphous structure can withstand a high-temperature oxidizing atmosphere (≥650 °C) only when it has undergone sufficient reduction for an extended period. Therefore, the coexistence of the active nanocatalysts and defective amorphous surface leads to a nearly 100% enhancement in the electrode resistance for the ORR over 200 h without significant degradation. These observations provide a new catalytic design strategy for using redox-dynamic perovskite oxide host materials.

Deactivation mechanism of catalyst in long-period experiment of 1,1,2-TCE dehydrochlorination

ABSTRACT VDC, as an important raw material for high barrier material PVDC and lithium-ion battery binder PVDF, had an increasing demand. The catalytic dehydrochlorination of 1,1,2-TCE to generate VDC was a green process route that was expected to replace the heavily polluting sodium hydroxide saponification process in industry. There was a certain research foundation for the catalytic dehydrochlorination of 1,1,2-TCE, among which the core problem was that the catalyst was prone to deactivation. Previous studies had calculated the average molecular structure of the spent catalyst surface species when coconut shell activated carbon was used as the support. In subsequent studies, alumina support had been proven to be a better carrier for dehydrochlorination of 1,1,2-TCE, and the selected catalyst had been used in long-period laboratory experiments. The results indicated that the catalyst life had been significantly improved. In the early stage of the reaction, the activity of the catalyst decreased rapidly. In the first 20 h, the conversion of 1,1,2-TCE decreased from 49.35% to 40.36%. From 21 h to 120 h, the conversion of 1,1,2-TCE decreased from 39.96% to 36.18%, tending to stabilize. After 120 h of reaction, the catalyst was extracted and elemental analysis, FTIR, and GPC characterization were performed on the spent catalyst surface species. The average molecular formula of the carbon deposits was obtained as C96.08H50.29Cl36.53. Compared with coconut shell activated carbon support, under the action of activated alumina support, the route of catalyst carbon deposition had changed, and the sediment was more composed of polyvinylidene chloride components. Under certain conditions, sediment formed a dynamic equilibrium, which explained why the activity of the catalyst gradually stabilized. This study revealed the catalytic mechanism of active alumina supported catalyst and the pathway of carbon deposits generation, which was of great significance for improving the lifespan of improved catalyst.

Formation and evolution of coke of pyrolytic volatiles of low-rank coal on the carbon-based catalysts

The catalytic upgrading of coal pyrolysis volatiles is an effective technique to achieve clean and efficient conversion of low-rank coal. However, a major problem in this process is catalyst deactivation caused by coke deposition. This study investigated the catalytic cracking effect of activated carbon and metal-modified activated carbon on coal pyrolysis volatiles. It also explained the physical and chemical properties of coke and its formation mechanism related to volatile cracking. The results indicate that phenolic oils, pitch, oxygen-containing compounds, and polycyclic aromatics are linearly related to the coke deposited on the surface of carbon-based catalysts. These compounds act as precursors and are easily transformed into coke via cracking, deoxidation, crosslinking, and polycondensation reactions when the cracking rate of volatiles does not match the hydrogen supply rate. The micro-morphology of coke is primarily composed of amorphous carbon, which is mainly found in pores ranging from 0.50 to 5.00 nm and on the outer surface of carbon-based catalysts. The chemical structure of coke primarily consists of large aromatic clusters containing at least six benzene rings and oxygen-containing cross-linking compounds with a high degree of graphitization and a low number of carbon structural defects. This results in an increase in radical concentration of carbon-based catalysts, as well as a decrease in combustion reactivity. The outcomes will aid in controlling coke deposition during catalytic cracking of pyrolytic volatiles of low-rank coal.

Decoding the Promotional Effect of Iron in Bimetallic Pt-Fe-nanoparticles on the Low Temperature Reverse Water-Gas Shift Reaction.

The reverse water-gas shift (RWGS) reaction is a key technology of the chemical industry, central to the emerging circular carbon economy. Pt-based catalysts have previously been shown to effectively promote RWGS, especially when modified by promoter elements. However, their active states are still poorly understood. Here, we show that the intimate incorporation of an iron promoter into metal-oxide-supported Pt-based nanoparticles can increase their activity and selectivity for the low temperature reverse water-gas shift (LT-RWGS) substantially and drastically outperform unpromoted Pt-based materials. Specifically, the study explores the promotional effect of iron in Pt-Fe bimetallic systems supported on silica (PtxFey@SiO2) prepared by surface organometallic chemistry (SOMC). The most active catalyst (Pt1Fe1@SiO2) shows high selectivity (>99% CO) toward CO at a formation rate of 0.192 molCO h-1 gcat-1, which is significantly higher than that of monometallic Pt@SiO2 (96% sel. and 0.022 molCO h-1 gcat-1). In-situ diffuse reflectance FT-IR spectroscopy (DRIFTS) and X-ray absorption spectroscopy (XAS) indicate a dynamic process at the catalyst surface under the reaction conditions, revealing distinct reaction pathways for the monometallic Pt@SiO2 and bimetallic PtxFey@SiO2 systems.

Cs‐Promoted Co Particles on Yttria‐Stabilized Zirconia as Coke‐Tolerance Methane Dry Reforming Catalyst under Elevated Pressure

Methane reforming with CO2 (dry reforming) co‐converts the two green‐house gases into synthesis gas and offers a promising way to integrate CO2 utilization into the current chemical infrastructure. One major obstacle for its industrial deployment is coke deposition on catalyst surface, in particular, under industrially relevant, pressurized operation conditions. Most catalytic investigations are conducted at atmospheric pressure, but the elevation in pressure poses a grand challenge for catalyst design. In this study, we demonstrate that Cs can promote carbon‐tolerance of Co catalyst supported on Yttria‐stabilized Zirconia under 20 bar, 850 oC with stochiometric feed flow for up to 100 h, which is often regarded as accelerated deactivation testing condition. Lowered amount and mostly CO2 gasifiable residue carbons are determined in Cs‐promoted spent Co‐catalyst, with respect to pristine Co catalyst. Kinetic studies reveal that Cs slows down coke deposition, while the essential reaction mechanism on pristine Co catalyst remains unaltered. Cs+ moieties absorb CO2 to afford Cs2CO3 that can release O* on adjacent Co surface to facilitate surface C* oxidation and simultaneously suppress carbon nucleation. The disclosure of the promoting effect of Cs on Co catalyst may have implications to other reforming catalyst and process design.

Study of the Use of Oxygenated Water as a Non-Toxic Molecule Model for Catalytic Testing of Pozzolana-PN and Iron-Based NOx Reducing Catalysts

During previous catalytic tests on the reducing power of NOx catalysts based on pozzolana and PN-black citric acid polymer, it was found that the use of the NO<sub>2</sub> model molecule poses a significant health and environmental risk. Thus, a project was launched to find another, much less harmful model molecule. Hydrogen peroxide H<sub>2</sub>O<sub>2</sub> was chosen, a molecule naturally secreted by the body to prevent pigment synthesis, with disinfectant, antiseptic and whitening properties widely used in various activities, including cosmetics. Consequently, catalytic tests of NOx-reducing power using hydrogen peroxide H<sub>2</sub>O<sub>2</sub> as a model molecule were carried out on two catalysts based on pozzolana and PN-black polymer of citric acid, PNP-Fe-water-15% and PNP-Fe-ethanol-15%, differing in the solvent used during their syntheses according to a procedure detailed in the bibliography and this manuscript. Pozzolana is a volcanic rock widespread in the volcanic mountains in the Vakinankaratra region of Madagascar. Its use as a support for catalysts based on PN-black polymer of citric acid and Iron-Fe enabled us to synthesize various catalysts, the characteristics and synthesis methods of which are detailed in this manuscript. In short, the catalytic test with hydrogen peroxide was conclusive, enabling a pragmatic comparison of the two catalysts tested, with the result that the catalyst synthesized with water PNP-Fe-water-15% is more active than the catalyst synthesized with ethanol PNP-Fe-ethanol-15%. This is due to the quality and difference in dispersion of the PN-black polymer molecules depending on the solvent used, which can have an impact on the nature of the catalyst surfaces and certain characteristics such as porosity. This dispersion is confirmed and viewed using an optical microscope to visualize the surface of a catalyst grain. Kinetic results from two proposed mechanisms for the reduction of H<sub>2</sub>O<sub>2</sub> hydrogen peroxide molecules using PNP-Fe catalysts also confirmed not only the proposed mechanisms, but also the higher activity of PNP-Fe catalysts synthesized with water, whose kinetic constants are much higher than those synthesized with ethanol.

Influence of iron content in palladium catalysts supported on alumina and their reduction conditions on the hydrodechlorination of diclofenac in aqueous solutions

Using the method of wet impregnation of alumina with iron and palladium nitrates, 1Pd0.5Fe and 1Pd10Fe catalysts modified with iron oxides were prepared with a target content of 1 wt % Pd, 0.5 or 10 wt % iron. The catalysts were compared with each other and with the monometallic catalyst 1Pd in the hydrodechlorination (HDC) of diclofenac (DCF) in dilute aqueous solutions at 30°C in batch and flow reactors after high-temperature (320°C) and mild (30°C) reduction; the latter was carried out in a batch or flow reactor. Using X-ray photoelectron spectroscopy (XPS), it was shown that after reduction at 320°C the surface of catalysts contains mainly Pd0, Fe2+ and Fe3+. The surface Fe2+/Fe3+ ratio increases as the iron content decreases. The reduction of Pd2+ to Pd0 is possible already at 30°C, but it proceeds much worse on the surface of 1Pd0.5Fe compared to 1Pd10Fe. According to XPS data, temperature-programmed reduction and infrared spectroscopy of diffuse reflection of adsorbed CO, modification with iron oxides increases the palladium content on the surface compared to 1Pd, promotes the emergence of new Pd–O–Fe centers, and affects the ability of palladium to be reduced. These effects increase with increasing iron content. Iron-modified catalysts reduced at 320°C showed similar activity and stability in the conversion of DCP in flow-through and batch systems. Unlike 1Pd0.5Fe, the 1Pd10Fe catalyst is highly efficient and stable even after mild reduction at 30°C. Under flow conditions with comparable DCF conversion, it provides increased selectivity in the HDC reaction of diclofenac compared to 1Pd, which is also active in hydrogenation.

W-based carbide derived from PW12@ZIF-8 as Pt-free catalyst on counter electrode of dye-sensitized solar cells for triiodide reduction

The preparation of counter electrodes (CEs) catalysts at different pyrolysis temperatures will directly affect the composition, morphology, and performance of the catalysts in dye-sensitized solar cells (DSSCs) applications. Herein, four W-based carbides catalysts were derived from H3PW12O40-based ZIF-8 metal–organic frameworks (PW12@ZIF-8) by in-situ pyrolysis at 600, 700, 800, and 900 ℃ under N2 atmosphere. The pyrolysis mechanism and structure characteristics of the prepared W-based carbides with temperature variation were confirmed by TG-DTG-DSC simultaneous, XRD, XPS, TEM, SEM and N2 adsorption/desorption, which exhibits the gradual transformation of PW12@ZIF–8 → WC-C→WC→W1-xC→W2C. Furthermore, the photovoltaic performance of four different W-based carbides as CEs catalysts for regenerating I3−/I− shuttles in DSSCs were identified by photocurrent-voltage (J-V) measurement, which achieved PCEs of 4.63, 4.91, 5.05 and 5.78 %, respectively. As a result, W2C (900 ℃) provide more vacancies and defects on the catalyst surface as abundant catalytic active sites, as well as promote the appearance of more pores and voids in the morphology to diffuse and permeate electrolyte due to the highest specific surface area, and the PCE value of 5.78 % was also superior to 5.51 % of Pt CE.

Exploring the potential of cobalt-based catalysts in the methane dry reforming for sustainable energy applications

Cobalt-based powder catalysts with different Co loadings were synthesized via wet impregnation using MgAl2O4 spinel as support. The catalytic properties of the solids were evaluated in the dry-reforming methane at different reaction temperatures and two CH4:CO2 ratios. The catalyst with higher cobalt content (13 %) presented superior performance due to increased Co0 species availability, confirmed by XPS analysis. Besides, this catalyst displayed remarkable resistance to carbon deposition at 550 °C and CH4:CO2 1: 1 ratio. In-situ DRIFT measurements demonstrated the formation and transformation of carbonate and hydrogen carbonate species during the DRM reaction, highlighting efficient CO2 and CH4 activation on the catalyst surface. Based on this data, a structured catalyst was deposited on top of the FeCrAlloy monolith, which was active, stable, selective for H2, and resistant against on/off cycles. Compared with the powder catalyst, the structured system displayed higher catalytic activity, possibly due to higher reducibility of metal species and improved heat transfer provided by the FeCrAlloy substrate. The results highlight the potential of Co-based structured catalysts for H2 or synthesis gas production processes.

Enhancing Ce-Co interfacial effects via special petal-pollen morphology construction to achieve efficient toluene removal

Interfacial effects provide an effective means to construct multi-metal interactions and design efficient catalysts for VOCs purification, while morphology construction remains a common tactic to optimize the efficiency of these catalysts. In the present work, the Co-Ce bimetal interface was effectively constructed by morphological regulation, and the coupling of the interfacial effect modulation and the special morphological structure was realized, resulting in superior catalyst performance. Among the series catalysts, CeCoOx-H demonstrated the optimized activity with 90 % toluene conversion at 250 °C while maintaining good results in a 50 h stability test. And the systematic characterization revealed that the structural changes and interfacial effects induced by morphological modulation would increase the structural defects, improving surface reactive oxygen and oxygen vacancy content, oxygen storage capacity, oxygen motivity and low-temperature reductivity, which account for promising catalytic performance of CeCoOx-H. Furthermore, in-situ DRIFTS revealed the following decomposition routes for toluene on the CeCoOx-H catalyst surface: toluene → benzyl alcohol → benzaldehyde → benzoate → phenol → maleate → acetate → formate → carbon dioxide. In particular, the decomposition of benzaldehyde and benzoate may be the key steps in toluene catalytic oxidation. Also, the characterization unveiled that the rich adsorption sites brought by the interfacial construction are not negligible in boosting the catalytic performance.

Oxygen octahedral void-confined iodine single-site RuO2 catalysts for water reduction

Iodine (I), with abundant extra-nuclear electrons and high electronegativity, can enhance the performance of catalysts by electronic tuning effects of I single-site. However, I atoms are always located at shallow surfaces of catalysts, leading to fast volatilization and subsequent poor catalytic stability. Herein, we conceive a single-site I doped RuO2 catalyst via heating RuI3 in air, wherein the I concentration gradually increases from shallow to deep surfaces. This ensures that partial I atoms are located in oxygen octahedral voids of RuO2 as single-site at deep surfaces of catalyst, avoiding I loss during catalysis. Impressively, I-introduction decreases the valence of Ru and strengthens the adsorption of *H on Ru actives, and then superior hydrogen evolution activity (14 mV @ 10 mA cm−2) is achieved in alkaline media. Additionally, both the confined effect of oxygen octahedral voids on I single atoms and stable I-O bonds make the catalyst durable for 50 h.

Simulated sunlight-driven photocatalytic activation of peroxydisulfate by core–shell Ag@SiO2/TiO2 nanocomposite for efficient methyl orange degradation

Herein, core–shell Ag@SiO2/TiO2 nanocomposites were synthesized and applied to activate peroxydisulfate (PDS) for wastewater purification. The Ag core and Ag-doped TiO2 shell were obtained by stober method and calcination method. The dispersion degree and size of Ag in TiO2 would influence the oxygen vacancy. Ag enhanced the visible absorption of TiO2 and activated PDS. Improved degradation performance was attributed to enhanced PDS activation by photogenerated e−, which separated h+and thus promoted methyl orange(MO) degradation. Reactive oxidative species were verified under dark and light conditions via quenching experiments and electron paramagnetic resonance tests, demonstrating SO4•–, h+, O2•–, and1O2were formed in light,whereasSO4•–, •OH, O2•–, and 1O2were responsible for MO degradation under dark conditions. The Ag@SiO2/TiO2/PDS/light system showed selectivity for removal of cationic dyes (e.g., methylene blue and malachite green) through adsorption and photocatalysis, whereas anionic dyes (e.g., MO) were degraded by photocatalysis alone. Besides, we found excess adsorption of micropollutant onto catalyst may be adverse to the activation of PDS. Therefore, the adsorption of oxidant (such as PDS) onto the catalyst surface would be beneficial for catalytic activation and micropollutant degradation, especially onto active sites. This work aims to provide a new avenue for core-shell structure catalyst synthesis in wastewater purification.

Facile one-pot synthesis of CuO–Bi2O3/MgAl2O4 catalyst and its performance in the ethynylation of formaldehyde

The CuO–Bi2O3/MgAl2O4 catalyst was synthesized via one-pot synthesis and used to catalyze formaldehyde (HCHO) ethynylation. Coprecipitation using Cu2+, Bi3+, Mg2+, and Al3+ nitrates and NaOH generated Cu and Bi oxides and spinel MgAl2O4 phase. The catalyst precursor was calcined at 450 °C. The catalytic performance of CuO–Bi2O3/MgAl2O4 in the synthesis of 1,4-butynediol via HCHO ethynylation was investigated. The presence of a new spinel phase enhanced the acid–base properties on the catalyst surface and prevented the aggregation of CuO particles. These properties resulted in improved CuO dispersion during calcination and CuO particle growth suppression, affording smaller CuO crystals. The MgAl2O4 support facilitated the reduction of Cu2+ to Cu+ and formation of abundant active species during the reaction. The catalyst exhibited abundant weakly basic, fewer strongly basic, and least acidic sites, which facilitated the adsorption of HCHO and acetylene. The catalytic performance of CuO–Bi2O3/MgAl2O4 demonstrated 97 % conversion and 80 % selectivity after the online monitoring of the ethynylation reaction for 6 h. The leaching of Cu during the reaction, as analyzed by inductively coupled plasma spectroscopy, was extremely low. Moreover, conversion and selectivity did not substantially change after eight cycles. In addition, the catalyst exhibited superior activity and long-term stability in the ethynylation reaction.

Concurrent oxygen evolution reaction pathways revealed by high-speed compressive Raman imaging.

Transition metal oxides are state-of-the-art materials for catalysing the oxygen evolution reaction (OER), whose slow kinetics currently limit the efficiency of water electrolysis. However, microscale physicochemical heterogeneity between particles, dynamic reactions both in the bulk and at the surface, and an interplay between particle reactivity and electrolyte makes probing the OER challenging. Here, we overcome these limitations by applying state-of-the-art compressive Raman imaging to uncover concurrent bias-dependent pathways for the OER in a dense, crystalline electrocatalyst, α-Li2IrO3. By spatially and temporally tracking changes in stretching modes we follow catalytic activation and charge accumulation following ion exchange under various electrolytes and cycling conditions, comparing our observations with other crystalline catalysts (IrO2, LiCoO2). We demonstrate that at low overpotentials the reaction between water and the oxidized catalyst surface is compensated by bulk ion exchange, as usually only found for amorphous, electrolyte permeable, catalysts. At high overpotentials the charge is compensated by surface redox active sites, as in other crystalline catalysts such as IrO2. Hence, our work reveals charge compensation can extend beyond the surface in crystalline catalysts. More generally, the results highlight the power of compressive Raman imaging for chemically specific tracking of microscale reaction dynamics in catalysts, battery materials, or memristors.

Diverse Effects of SO2-Induced Pt-O-SO3 on the Catalytic Oxidation of C3H6 and C3H8.

The effects of sulfur dioxide (SO2) in the catalytic purification of short-chain hydrocarbons are still controversial, and the exact role of SO2 on adsorption and reaction pathways during the catalytic oxidation of different volatile organic compounds (VOCs) remains unclear. Herein, a three-dimensional ordered macroporous Ce0.8Zr0.2O2 supported Pt nanoparticle monolithic catalyst (Pt/OM CZO) was synthesized to investigate these effects. Our findings uncover the diverse effects of SO2: Upon SO2 treatment, the coupling between the S 3p and Pt 5d orbitals promotes the Pt-O-SO3 structure in situ formed on the catalyst surface. The propene (C3H6) molecule readily binds with the oxygen atom in Pt-O-SO3, resulting in the accumulation of acetone and carbon deposition, thereby hindering C3H6 oxidation. Conversely, a cleaved oxygen atom within the Pt-O-SO3 structure enhances propane (C3H8) adsorption and activates the C-H bond, facilitating C3H8 oxidation. These insights are pivotal for advancing the frontier of sulfur-tolerant catalysts, addressing both economic and environmental challenges.

Comparing low-temperature NH3-SCR activity, operating temperature window and kinetic properties of the Mn-Fe-Nb/TiO2 catalysts prepared by different methods

In order to overcome the shortcomings of traditional V-based catalysts, such as poor low-temperature activity, narrow temperature window, and toxicity. Therefore, the Mn-Fe-Nb/TiO2 catalysts were prepared using impregnation (IM), citric acid complexation (CA), co-precipitation (CP), hydrothermal synthesis (HY), and sol–gel (SG) methods to develop novel NH3 selective catalytic reduction (NH3-SCR) catalysts with excellent low-temperature activity, a wide temperature window, and environmental friendliness. Their NH3-SCR catalytic activity was evaluated, followed by a detailed analysis of their morphology, structure, specific surface area, chemical state, redox properties, acidity, and interactions using X-ray diffraction (XRD), Bruaner-Emmet-Teller (BET), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), NH3 temperature-programmed desorption (NH3-TPD), and Fourier transform infrared spectroscopy (FTIR) techniques. The 5Mn-7Fe-4Nb/TiO2-SG catalyst, prepared via sol–gel, exhibited the highest denitrification (de-NOx) activity and the widest operating temperature window, achieving over 80% Nitric oxide (NO) conversion at 180–350 °C and a peak conversion of 97% at 250 °C. The XRD, BET, SEM, and HR-TEM characterization results showed that the catalyst prepared using the sol–gel method had the smallest particles, the highest specific surface area, and the greatest dispersion. XPS and NH3-TPD results revealed that the catalyst prepared using the sol–gel method possessed the highest surface adsorbed oxygen (Oα) content and the largest number of acidic sites. H2-TPR and FTIR analyses indicated that the catalyst prepared using the sol–gel method enhanced the reduction capacity and possessed the strongest interaction forces among support-active-promoter components. Steady-state kinetic tests confirmed that in the NH3-SCR reaction, the rate-determining step was the adsorption activation of NO on the catalyst surface. The sol–gel method reduced the activation energy for de-NOx reactions, enhancing the low-temperature activity of the catalyst.

Mn3O4-FeS2/Fe2O3 composite as peroxidase-mimics for the degradation of Bisphenol A

Due to the benefits of artificial peroxidase-like enzymes, Flower-like Mn3O4-FeS2/Fe2O3 composites with multiple active sites prepared by a one-step solvothermal method.The synergistic cyclic reaction between Mn and Fe on the catalyst surface enhances the generation of active radicals, which together promote the efficient degradation of BPA. In the presence of hydrogen peroxide (H2O2), Mn3O4-FeS2/Fe2O3 could generate hydroxyl radicals (·OH) and superoxide radicals (·O2-) in buffer solution of pH=4.5 and catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxidation products (ox TMB). The steady-state kinetic constants (Km) of TMB and H2O2 were obtained by Michaelis-Menten and Lineweaver-Burk models, which are 1.34 mM and 1.00 mM, respectively. This reveals the nice catalytic efficiency of Mn3O4-FeS2/Fe2O3 as enzyme mimics. Under the condition of 10 mg Mn3O4-FeS2/Fe2O3 catalyst, 100 μL H2O2 and pH = 4.5, the degradation efficiency of Bisphenol A (BPA) reaches 100 % when treating 40 mL of 50 mg L−1 BPA for 30 min at room temperature. Moreover, after 5 cycles of degradation, the BPA degradation efficiency of 85.8 % was still maintained. Therefore, the as-prepared Mn3O4-FeS2/Fe2O3 sample could potentially be applied in wastewater treatment.

Restructuring surface frustrated Lewis pairs of MgAl-LDH through isomorphous Co doping for accelerating photocatalytic CO2 reduction

The adsorption of carbon dioxide on the catalyst surface is often neglected, and the improvement of adsorption activation capacity is important to realize the efficient conversion of carbon dioxide. In this paper, a novel layered double hydroxide Co-MgAl-LDH (CML) with frustrated Lewis pairs (FLPs) was successfully prepared by one-step hydrothermal doping of transition metal Co, which Co2+ and the oxygen vacancies brought about by the doping (Co2+-Vo) are the Lewis acid site, and adjacent hydroxyls are the Lewis base site, and In-situ experiments and Density Functional Theory (DFT) demonstrated that the FLPs effectively enhanced the CO2 adsorption activation capacity of CML. The present work provides a new idea for modifying Layered double hydroxides (LDH) to construct FLPs, and also offers new hope for constructing high-performance LDH-based CO2 reduction photocatalysts.