Catalyst Precursor Research Articles

Redox and Photochemical Reactivity of Cerium(IV) Carbonate and Carboxylate Complexes Supported by a Tripodal Oxygen Ligand.

The protonolysis and redox reactivity of a Ce(IV) carbonate complex supported by the Kläui tripodal ligand [(η5-C5H5)Co{P(O)(OEt)2}3]- (LOEt-) have been studied. Whereas treatment of [Ce(LOEt)2(CO3)] (1) with RCO2H afforded [Ce(LOEt)2(RCO2)2] (R = Me (2), Ph (3), 2-NO2C6H3 (4)), the reaction of 1 with PhCH2CO2H resulted in formation of a mixture of Ce(IV) (5) and Ce(III) (6) carboxylate species. In benzene in the dark, 5 was slowly converted into 6 via Ce(IV)-O(carboxylate) homolysis. Recrystallization of a mixture of 5 and 6 from hexane led to isolation of yellow crystals of 6 that were identified as [Ce(LOEt)2(PhCH2CO2)]. Treatment of 1 with sulfamic acid, trifluoroacetamide, and trifluoromethanesulfonamide gave [Ce(LOEt)2(SO3NH)2] (7), [Ce(LOEt)2(CF3CONH)2] (8), and [Ce(LOEt)2(CF3SO2NH)2] (9), respectively. The crystal structures of 2, 4, and 6-8 have been determined. H atom transfer (HAT) of 2,6-di-tert-butylphenol and 9,10-dihydroanthracene (DHA) with 1 afforded 3,3',5,5'-tetra-tert-butyldiphenoquinone and anthracene, respectively. The oxidation of DHA with 1 under air yielded anthracene and anthraquinone. While 1 is stable in acetonitrile, it is readily reduced to a Ce(III) species in tetrahydrofuran. In air, 1 reacted with tetrahydrofuran to produce tetrahydrofuran hydroperoxide that can reduce the Ce(IV) carbonate rapidly. Upon irradiation with blue LED light, the Ce(IV)-LOEt carboxylate complexes underwent facile decarboxylation via Ce-O homolysis. 1 proved to be an efficient catalyst precursor for decarboxylative oxygenation of arylacetic acids. For example, irradiation of phenylacetic acid with blue LED light in the presence of 5 mol % of 1 under air afforded benzyl alcohol and benzaldehyde in 10 and 90% yield, respectively.

Enhancing activity and selectivity of palladium catalysts in ketone α-arylation by tailoring the imine chelate of pyridinium amidate (PYA) ligands.

Even though α-arylation of ketones is attractive for direct C-H functionalization of organic substrates, the method largely relies on phosphine-ligated palladium complexes. Only recently, efforts have focused on developing nitrogen-based ligands as a more sustainable alternative to phosphines, with pyridine-functionalized pyridinium amidate (pyr-PYA) N,N'-bidentate ligands displaying good selectivity and activity. Here, we report on a second generation set of catalyst precursors that feature a 5-membered N-heterocycle instead of a pyridine as chelating unit of the PYA ligand to provide less steric congestion for the rate-limiting transmetalation of the enolate. To this end, new heterocycle-functionalized PYA palladium(ii) complexes containing an oxazole (5b), N-phenyl-triazole (5c), N-methyl pyrazole (5d), N-phenyl-pyrazole, (5e), N-xylyl-pyrazole (5f), and N-isopropyl-pyrazole (5g) were synthesized compared to the parent pyr-PYA complex 5a. Less packing of the palladium coordination sphere was evidenced from solid state X-ray diffraction analysis. While the catalytic activity of the oxazole system was lower, all other complexes showed higher activity. In particular, complex 5g comprised of an electron-donating and sterically demanding iPr-pyrazole chelating PYA ligand is remarkably stable towards air and moisture and shows outstanding catalytic activity with complete selectivity (>99% yield) and turnover frequencies up to 1200 h-1, surpassing that of parent 5a by one order of magnitude and rivalling the most active phosphine-based palladium systems. Kinetic studies demonstrate a first order rate-dependence on palladium and the substrate. Some deviation of linearity together with poisoning experiments suggest a mixed homogeneous/heterogeneous pathway, though the reproducible kinetics of in situ catalyst recycling experiments strongly point to a molecularly defined active species, demonstrating the high potential of PYA-based ligands.

Hollow-SiO2@Cu x Zn y Mg z Al-LDHs as catalyst precursors for CO2 hydrogenation to methanol.

We report a new synthetic strategy for preparing well-organised, spherical and mesoporous, mixed-metal, hollow-core@layered double hydroxides. Hollow-SiO2@Cu x Zn y Mg z Al-LDHs (x + y + z = 2.32 ± 0.06) were prepared by exploiting a unique "memory effect" feature of LDH materials. The reconstruction with simultaneous incorporation of Cu2+ and Zn2+ into the LDH shell was achieved by exposing hollow-SiO2@Mg2Al-LDO to an aqueous solution containing Cu2+ and Zn2+ cations. The effect of a single reconstruction step with various concentrations of Cu2+ and Zn2+ solutions (20-80 mM), as well as the implementation of five successive cycles of calcination-reconstruction on the chemical composition, morphology, texture and structure of the resulting materials are described. Hollow-SiO2@Cu x Zn y Mg z Al-LDHs are precursors to active catalysts for CO2 hydrogenation to methanol. The most active catalyst exhibits a space-time yield for methanol of 1.68 gMeOH gCu -1 h-1 at 270 °C (3 : 1 CO2 : H2, 30 bar) which represents a 1.7-fold increase in space-time yield compared to commercial Cu/ZnO/Al2O3 catalyst under the same conditions.

Catalytic Pyrolysis of Waste Textiles for Hydrogen-Rich Syngas Production over NiO/Al2O3 Catalyst

Hydrogen production through the catalytic pyrolysis of low-value organic solid waste offers a promising low-carbon and environmentally friendly pathway. However, the design of efficient hydrogen-producing catalysts remains a significant challenge. Herein, NiO/Al2O3 as a catalyst precursor was utilized to investigate the effects of reduction temperature gradients (300–800 °C) on the distribution of three-phase products and the composition of gaseous products during the pyrolysis of waste textiles. Compared to unreduced NiO/Al2O3, increasing the reduction temperature (300–700 °C) led to a gradual decrease in liquid-phase products and a notable increase in gas-phase products, with the latter rising by 10.59% at 700 °C. Most strikingly, hydrogen gas production increased by 6.42% under the same conditions. Multi-characterization analyses, including XRD, TEM, and H2-TPR, revealed significant aggregation of highly dispersed Ni species in NiO/Al2O3 at higher reduction temperatures. The emergence of XRD characteristic peaks and the (111) crystal face of metallic Ni (Ni0) became apparent at 700 °C. More importantly, the XPS test inferred that the increasement of hydrogen-rich gas production was ascribed to the appropriate Ni0/Ni2+ ratio, and the highest hydrogen yield of 41.50% was achieved as the Ni0/Ni2+ ratio reached about 1.57. This work not only provides an effective solution for the consumption of waste textiles, but also converts it into high value-added hydrogen-rich gas.

Regeneration of the Catalyst Precursor for Hydroconversion of a Blend of Petroleum Tar and Polymer Waste

Regeneration of the Catalyst Precursor for Hydroconversion of a Blend of Petroleum Tar and Polymer Waste

Eco-friendly and ready-to-market polyurethanes: a Design of Experiment-guided substitution of toxic catalyst and fossil-based isocyanate.

In this contribution, we tackle the replacement of the Hg-based catalyst and fossil-derived isocyanate precursors toward the formulation of a more sustainable polyurethane thermosetting resins (PUs), emulating the performance of a fully fossil-based one employed in industrial encapsulation of optoelectronics. A mixed Bi-Zn catalyst and a 71% bio-based isocyanate are exploited at this aim through multivariate chemometric approaches, namely Design of Experiment (DoE). DoE allows us to investigate the effect of different formulation factors on selected parameters, such as the film flexibility and transparency or the gel time. More in detail, it is found that a low amount of Zn-rich catalytic mixture leads to a ready-to-market polyurethane only when a fossil-based isocyanate is used. Differently, PUs formulated with bio-based isocyanate, albeit showing a higher bio-based content, present an insufficient optical purity, jeopardizing their market acceptability. Nevertheless, adding a negligible amount of a specific long chain fatty acid as reactivity modulator in the formulation leads to a bubbles-free and ready-to-market resin showing an impressive 65% w/w content of circular and bio-based components.

The MOF‐Derived Ag@M‐N/Al‐O Catalyst for Highly Selective Electrocatalytic Reduction of CO2 to CO

ABSTRACTFor ensuring the economic feasibility of the electrochemical carbon dioxide reduction reaction (CO2RR), which can be used to reduce the catalyst load and increase the catalytic activity of CO2RR by using carrier materials. Here, we report the systematic alteration of metal chloride on bipyridine groups in MOF‐253(Al) using modified metal–organic frameworks (MOFs) as precursors and the introduction of Ag nanoparticles to prepare catalysts Ag@M‐N/Al‐O (M = Co, Ni, Zn, Cu). EDS spectra showed the uniform dispersion of Ag nanoparticles. In addition, the chemical structure of the catalyst was analyzed by XPS and PXRD, which proved the existence of M‐N and Al‐O bonds. The interaction with Ag nanoparticles leads to electron density reconstruction, and the stable *COOH intermediates with electron delocalization enhanced by polymetallic electron configuration modulation are conducive to CO production. The results show that Ag@Co‐N/Al‐O can achieve 85.6% FE for CO and has good stability within 12 h. This work provides a new idea for CO2RR material design using MOFs as a precursor catalyst.

Conversion of carbohydrates to organic acids in aqueous medium using aluminum nitrate as the catalyst precursor

Conversion of carbohydrates to organic acids in aqueous medium using aluminum nitrate as the catalyst precursor

Experimental optimization for synthesis of cerium-doped titanium dioxide nanoparticles by modified sol-gel process

A systematic experimental optimization procedure was developed for the synthesis of cerium-doped titanium dioxide nanoparticles (CeTNPs) based on modified sol-gel process. The nanocomposite was prepared using titanium tetraisopropoxide (TTIP) as a catalyst precursor, while utilizing the non-ionic surfactant Triton X-114 in cyclohexane as a stabilizing agent. The synthesis process was optimized by identifying the main experimental factors that affect the properties of the nanoparticles, primarily the structural phase and particle size. The synthesized samples were characterized by X-ray diffraction (XRD) for phase and size, field emission scanning electron microscope (FE-SEM) for morphology, particle size analyzer (PSA) for size distribution, and Brunaur, Emmett, and Teller (BET) for surface area and pores characteristics. The photocatalytic activity of the optimized sample was tested for the removal of methyl orange (MO) and lead (II) from aqueous solutions, and the results indicate superior performance as the catalyst uptakes were 14.8 mg/l and 11.4 mg/l for methyl orange and lead (II), respectively.The main highlights of the proposed procedure are as follows:•Identification of the key variables impacting the structural and morphological properties.•Establishing the levels of each factor based on experimental findings.•Generation of all possible combinations of factors based on ANOVA, then characterization of the synthesized material from every possible combination.

Rhodium‐Catalyzed Reductive Hydroformylation of Polyunsaturated Vegetable Oils Assisted by Triethylamine/N‐methylimidazole Ligands Combination

AbstractIn this work, the reductive hydroformylation of linseed and sesame oils was carried out successfully by using a rhodium catalyst precursor associated to triethylamine/N‐methylimidazole ligands combination. Interestingly, in the presence of triethylamine and N‐methylimidazole at a precise ratio with respect to rhodium, the isomerization reaction can be inhibited and control experiments realized on methyl linoleate and methyl linolenate have clearly shown that no conjugated products were formed. This new catalytic system is full of interest since the yields in alcohols, after 24 h, are equal to 21% and 15% for Rh/triethylamine combination, whereas equal to 58% and 63% for Rh/triethylamine/N‐methylimidazole combination, for linseed and sesame oils, respectively.

Development of Fe/N/C Type Oxygen Reduction Catalysts Using Carbon Supports Derived from Cellulose Paper by a Microwave Method

Introduction Effective utilization of abundant forest resources is crucial in Japan, which has vast forest reserves. Cellulose, which constitutes half of plants, has recently garnered attention as a novel material, such as cellulose nanofiber. Kyotani et al. reported that high-yield carbon materials retaining the original shape can be obtained by high-temperature treatment of cellulose-based paper treated with methanesulfonic acid1.We have been preparing Fe/N/C oxygen reduction catalysts using the carbon materials prepared by the method as a support; however, the oxygen reduction activity was insufficient. This study aimed to enhance the oxygen reduction reaction (ORR) activity by employing the microwave method for the preparation of carbon supports, synthesis of catalyst precursors, and drying treatment. Experimental Cellulose paper (toilet paper (TP), Nippon Paper Crecia) was immersed in 1.0 M methanesulfonic acid and air-dried for more than two days in a container with a filter attached to the top. The air-dried sample was sandwiched between two carbon plates, placed in an electric furnace, and heat-treated at 800°C for 1 h under Ar atmosphere with a heating rate of 5.5°C/min to obtain a carbonized sample. The sample was heat-treated using microwave oven (ER-SS17A, TOSHIBA) (denoted as MWtre). The sample was pulverized into carbon powder, mixed with 1,10-phenanthroline monohydrate, zinc acetate dihydrate, iron(II) acetate, and Milli-Q water, and heated and stirred for 30 min. Subsequently, the catalyst precursor slurry was obtained by heating using a microwave oven (RE-S5C-W, SHARP) (denoted as MWref). The obtained catalyst precursor slurry was dried using a microwave oven (ER-SS17A, TOSHIBA) to obtain the catalyst precursor (denoted as MWdry). The heat treatment was carried out in two stages. In the first stage, the catalyst precursor was placed in a SUS316 sealed container, replaced with Ar, heated to 800°C at 14°C/min, and then quenched to room temperature to prepare an intermediate material. In the second stage, the intermediate material was placed on a quartz boat and heat-treated at 1050°C for 20 min under Ar flow to obtain the catalyst.The oxygen reduction activity of the prepared catalyst was evaluated using the rotating ring-disk electrode (RRDE) method. A 2.00 mg/mL catalyst-2-propanol suspension, prepared by sonication and shaking, was cast on the GC electrode of a Pt ring-glassy carbon (GC) disk electrode (φ 6 mm), air-dried, and then 0.1 wt% Nafion® was cast and air-dried to prepare a catalyst-modified electrode. The evaluation of ORR activity was performed in 0.1 M sulfuric acid using the modified electrode as the working electrode, a GC electrode as the counter electrode, and RHE as the reference electrode. Results and discussion Fig. 1 shows the polarization curve and the efficiency of four-electron reduction (%H2O) obtained by the RRDE method. For comparison, the results for the catalyst prepared using the conventional method (refluxing for 24 hours followed by drying using a rotary evaporator) are also shown in Fig. 1 (quoted as EVAdry). The onset potential (@0.1 mA mg−1) derived from the oxygen reduction reaction was improved by 0.012 V compared to the conventional method. The efficiency of 4-electron reduction (@0.6 V vs. RHE) was improved by 8.9 – 21.1% compared to the conventional method. References (1) M. Kyotani, K. Hiratani, T. Okada, S. Matsushita, and K. Akagi, Global Challenges, 1, 1700061 (2017). Figure 1

Oxide-Metal Transition Processes of CuxO Foams during CO2RR Probed by Operando Quick-XAS

Electrochemical CO2 reduction reaction (CO2RR) is a promising alternative for large-scale production of hydrocarbons. However, there are still some challenges including poor product selectivity and highly complex multiple-step reaction mechanisms.[1,2] To enhance the electrochemically active surface area and create more active surface sites, one of the promising approaches is the use of partial or complete (surface) oxidation of nanostructured copper materials. These Cu oxide precursor catalyst materials are not stable during the cathodic potentials applied for CO2RR, but still show an enhanced selectivity for the formation of C2+ products.[3,4] Interestingly, few studies proposed that oxygen can be present under CO2RR conditions in a few nm thick amorphous copper layer, while DFT calculations indicate that no subsurface oxygen remains thermodynamically stable at these highly cathodic potentials.[5-7] So far, only Valesco-Vélez et al. studied the Cu oxidation state changes (Cu2+ and Cu+ to metallic Cu) during CO2RR in CO2-saturated 0.1 M KHCO3 probed by operando X-ray absorption spectroscopy (XAS).[8] However, for pure CuO no reduction to metallic copper or Cu2O even at highly cathodic conditions is found, due to the formation of a copper carbonate passivation layer.[8] Thus, it is still poorly understood how the structure of the Cu/CuxO precursor materials and their simultaneous reduction processes to metallic copper influence the CO2RR product distribution and the overpotential required for hydrocarbon formation. Recently, we have shown the critical potential of oxide-metal transition processes for a Cu oxide foam annealed at 300 °C in air probed by operando XAS, X-ray diffraction (XRD), and Raman spectroscopy techniques.[9,10]Using Cu K-edge Quick-XAS technique, we aim to understand the potential-dependent reduction of different Cu2+:Cu+ ratios to Cu0 for nanoporous CuxO foam precursor catalysts under CO2RR conditions. The CuxO foams were prepared by electrodeposition and subsequent thermal annealing between 100 and 450 °C in air to generate the different Cu2+:Cu+:Cu0 ratios. Initially, from ex-situ XANES, XRD, and XPS analyses, we found that a rise in annealing temperature leads to an increase in the proportion of Cu2+ species and their degree of crystallinity within the CuxO foams. After annealing at 100 °C and 200 °C, the CuO phase/species are amorphous and mainly found at the surface of the foam. Once the annealing temperature reaches 300 °C or higher, the CuO phase is entirely crystalline.With these different chemical states of the precursor catalyst, the Cu oxide-metal transition kinetics during cathodic potential increment (ΔE = 100 mV), step (ΔE > 100 mV), and jump (ΔE > 500 mV) experiments in CO2-saturated 0.5 M KHCO3 were comprehensively investigated using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) and Linear Combination Fit (LCF) analyses of the operando Cu K-edge Quick-XANES data. Our results demonstrate that different oxide-metal transition kinetics were found strongly dependent on the initial abundance of Cu2+ species and precursor structure (ordered vs. amorphous) as well as on the applied potential protocol to the CuxO foam precursor catalysts. More precisely, a high initial population of crystalline CuO, which is found for the CuxO foams annealed at 300 °C and 450 °C, leads to a significant shift of the oxide-metal transition potential towards lower cathodic overpotentials. For example, for the CuxO foam annealed at 450 °C (rich in crystalline CuO phases) the oxide-metal transition potential is shifted to 0 VRHE, while for the foam annealed at 100 °C this transition occurs at – 0.6 VRHE. Furthermore, smaller potential increments increase the formation and accumulation of Cu+ species, thereby slowing down the reduction kinetics. For the CuxO foam annealed at 200 °C, we could observe a full reduction to metallic Cu if jumping from OCP directly to – 0.5 VRHE, whereas no full reduction took place if using incremental potentials before applying – 0.5 VRHE.Overall, we show the substantial influence of crystalline CuOand the applied potential protocol on the reduction of CuxO foam precursor materials to metallic Cu during CO2RR.

Improvement of Photocatalytic Water Splitting Activity by Facet-Selective Loading of Ultrafine Rhodium–Chromium Mixed-Oxide Cocatalyst

<Background>Water-splitting photocatalysts capable of producing hydrogen from light and water have attracted much attention toward the realization of a carbon neutrality. In such semiconductor photocatalysts, there are crystal planes where excited electrons and holes can easily reach.1) Therefore, further enhancement of water splitting activity can be expected if the appropriate co-catalyst can be selectively loaded onto the appropriate crystal face. Although the conventional method of supporting cocatalysts by photoelectrodeposition can selectively support cocatalysts on crystalline surfaces, it is difficult to control the particle size due to the principle of the preparation method. On the other hand, we have developed a method to support ultrafine particles (~1 nm in diameter) on photocatalysts (cluster deposition method) and have succeeded in improving their water splitting photocatalytic activity.2,3) However, in this method, the fine auxiliary catalysts were loaded non-selectively on the crystalline surface, and the miniaturization effect was not efficiently utilized. In this study, we attempted to further improve the water splitting activity by developing a "crystal-facet-selective ultrafine catalyst loading method". A rhodium (Rh) complex, which acts as a hydrogen production assistant catalyst, is selectively loaded onto a crystal face where excited electrons can easily reach, while maintaining the fine state of the complex.<Experimental>Eighteen-facet strontium titanate (STO) with exposed {100} (hydrogen-producing) and {110} (oxygen-producing) planes was used as a photocatalyst support, and glutathionate-protected Rh complex (Rh:SG) was used as a catalyst precursor. First, a chromium oxide film was formed on STO, and then Rh:SG was adsorbed. In this process, 1) protection of the {110} surface by alcohol and 2) enhancement of adsorption on the {100} surface by pH adjustment and photo irradiation were attempted. The target photocatalyst was then prepared by calcination and photoirradiation (this method). As a comparison, photocatalysts supported by the conventional photoelectrodeposition method and the cluster adsorption method were also evaluated.<Results and Discussion>Transmission electron microscopy (TEM) revealed that fine Rh particles (average particle size: 1.2 ± 0.2 nm) were observed on the {100} plane of the STO prepared by this method, whereas these particles were hardly observed on the {110} plane, indicating that Rh particles were successfully loaded in a fine and crystal facet-selective manner (Fig. 1). From Fourier transform infrared spectroscopy measurements, it was confirmed that the alcohol added during the preparation selectively adsorbed on the {110} plane on STO, which is thought to have suppressed the adsorption of Rh:SG on the {110} plane. It is also suggested that photo-reductive desorption of the ligand occurred by photo-irradiation during Rh:SG adsorption, which promoted Rh:SG loading on the {100} plane where the excited electrons reach. The photocatalysts prepared by this method showed 2.6- and 1.4-fold higher water splitting activity than those prepared by conventional photodeposition and cluster adsorption, respectively (Fig. 1). This increase in water splitting activity is assumed to be induced by 1) the increase in specific surface area due to the miniaturization of Rh cocatalyst and 2) the enhancement of charge separation due to the selective loading of cocatalyst on the crystalline surface.4)1) K. Mu et al., Energy Environ. Sci., 2016, 9, 2463‒2469.2) D. Yazaki, T. Kawawaki, Y. Negishi et al., Small, 2023, 19, 2208287.3) D. Yazaki, T. Kawawaki, Y. Negishi et al., Energy Adv., 2023, 2, 1148‒1154.4) D. Hirayama, T. Kawawaki, Y. Negishi et al., submitted. Figure 1

Ligand-Functionalized Organometallic Polyoxometalate as an Efficient Catalyst Precursor for Amide Hydrogenation.

Amide hydrogenation is an important process for producing amines, with the development of efficient heterogeneous catalysts relying on the creation of bimetallic active sites where the two components interact synergistically. In this study, we develop a method for preparing catalysts using ligand-functionalized organometallic polyoxometalates by synthesizing a Rh-Mo organometallic polyoxometalate, [(RhCpE)4Mo4O16] (CpE = C5(CH3)3(COOC2H5)2), with Rh-O-Mo interfacial structures and ethoxycarbonyl-functionalized ligands as a catalyst precursor. The activity of supported Rh-Mo catalysts for amide hydrogenation depend on the precursor used, with [(RhCpE)4Mo4O16] showing the highest activity, followed by [(RhCp*)4Mo4O16] (Cp* = C5(CH3)5), and then RhCl3 combined with (NH4)6[Mo7O24]·4H2O. The catalyst prepared from [(RhCpE)4Mo4O16] effectively hydrogenates tertiary, secondary, and primary amides under mild conditions (0.8 MPa H2, 353-393 K), demonstrating a high activity and selectivity (conversion: 97%, selectivity: 76%) for primary amide hydrogenation under NH3-free conditions. Furthermore, we determine that carbonyl oxygen atoms in CpE ligands contribute to the electrostatic interaction with Al2O3, leading to the high dispersibility of [(RhCpE)4Mo4O16] on the support. We conclude that the high efficiency of [(RhCpE)4Mo4O16] as a catalyst precursor originates from the effective formation of Rh/Mo interfacial active sites, which is assisted by the electrostatic interaction between the CpE ligands and support.

Synthesis and characterization of titanium oxynitride catalyst via direct ammonia nitridation of titanium polyacrylate for oxygen reduction reaction

A titanium oxynitride catalyst for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells was synthesized through the direct ammonia nitridation of titanium complexes. Titanium polyacrylate was employed as the catalyst precursor, and the effect of the calcination temperature between 600 and 1000 °C on the catalyst structure was studied. The catalysts were characterized via X-ray diffraction, X-ray absorption spectroscopy, transmission electron microscopy, cyclic voltammetry, and powder electrical resistivity measurements. The formation of titanium oxynitride particles and deposited carbon was observed for all the samples; however, significant variations in the catalyst structure and catalytic activity were also observed. With an increase in the calcination temperature, nitridation of titanium oxynitride progressed, and the conductivity of the catalyst powder increased. The highest rest potential and ORR current density were achieved with calcination at 800 °C. Importantly, the results suggest that maintaining an optimal nitrogen doping level within the catalyst particles, along with ensuring the formation of electroconductive deposited carbon, is essential for achieving a high ORR current. This work introduces the direct ammonia nitridation of metal complexes as a promising process for designing metal oxynitride catalysts.

DNA Duplex Containing Ag+-Mediated Cytosine-Cytosine Base Pairs as a Catalyst Precursor for the 4-Nitrophenol Reduction with NaBH4.

Catalytic applications of DNA duplexes containing Ag+-mediated cytosine-cytosine base pairs (C-Ag+-C) have not been well investigated. In this study, we demonstrate a novel approach for forming highly active DNA-capped Ag nanoparticle (DNA-AgNP) catalysts for the reduction of 4-nitrophenol (4-NP) using sodium borohydride (NaBH4). This approach is based on the in situ generation of DNA-AgNPs from DNA duplexes containing C-Ag+-C (DNA duplex-Ag+). UV-vis spectroscopic analysis suggests that the DNA duplex-Ag+ complex acts as an excellent catalyst precursor for 4-NP reduction with NaBH4. Transmission electron microscopy observations of the reaction solution after the 4-NP reduction reaction using DNA duplex-Ag+ provided detailed experimental insights into the mechanism of the catalytic activity of DNA duplex-Ag+ for 4-NP reduction. In the reaction solution, DNA-AgNPs were initially formed (DNA duplex-Ag+ + NaBH4 → DNA-AgNPs) and then served as water-soluble catalysts for 4-NP reduction. Notably, the catalytic properties of the DNA-AgNPs generated in situ were affected by the DNA strand length and sequence. The properties of DNA duplex-Ag+ may provide a new application of DNA molecules containing metallobase pairs as water-soluble catalyst precursors.

Morphology‐Dependent Catalytic Activity of ZnFe2O4 Spinel Toward Light Olefins from Fischer–Tropsch Synthesis

AbstractThe shape‐defined ZnFe2O4 spinel with cubic and octahedral morphology was hydrothermally synthesized, respectively, and used as catalyst precursor for Fischer–Tropsch synthesis (FTS). The structure of ZnFe2O4 spinel was changed to ZnO and Fe5C2 (Fe5C2/ZnO) after reduction and carbonization. Interestingly, ZnFe2O4 with cubic morphology exhibited much higher catalytic activity and selectivity toward low‐carbon olefins (C2–C4) than the octahedral one under identical conditions, and the latter tended to produce the saturated alkanes. The primary properties of ZnFe2O4 materials before and after reduction were systematically studied through a series of characteristic technologies to reveal the difference in catalytic performance between the two ZnFe2O4 spinels with different morphologies.

Carbonaceous catalyst boosting conversion kinetics of Na2S in Na-ion batteries

Conversion-type metal sulfide anode with high theoretical capacity has received increasing attention in Na-ion batteries (SIBs), but the irreversible conversion of Na2S intermediate in charging process usually engenders low rate capability and poor cycling stability. Herein, guided by DFT calculation, a new-type carbonaceous graphitic carbon nitride (g-CN) catalyst is first reported to boost conversion kinetics of Na2S intermediate to pristine MoS2 in SIBs. Notably, the large chemisorbed energy, high selectivity and low catalytic energy barrier of g-CN catalyst can ensure its affluent charge transfers to Na2S intermediate, which chemically anchor and decompose Na2S intermediate for catalyzing its reversible conversion. Moreover, the microfluidic strategy is developed to enhance the mass diffusion of g-CN catalyst precursors into MoS2 skeleton for facilitating their subsequently covalent bonding process. The covalent bonding of g-CN catalyst on 1T-MoS2 (1T-MoS2/g-CN) superlattice with strong interfacial interaction via C-Mo bond can greatly promote Na+-storage kinetics of MoS2 in discharging process and reversible conversion reaction of Na2S intermediate to pristine MoS2 in following charging process, which is further evidenced by DFT calculation and in-situ characterizations. Consequently, the 1T-MoS2/g-CN superlattice reveals superb rate capacity and excellent cycling stability.

Surface microstructure of magnetic blast furnace dust and its correlation with persulfate catalytic performance: Laying foundation for its innovative applications as a catalyst precursor

The treatment of steelmaking wastes, particularly blast furnace dust (BFD), presents challenges for steel plants. Rich in iron (Fe) and carbon (C), BFD has potential for reuse. This study systematically investigated the surface microstructure of BFD’s magnetic fraction (BFD-M) and its role in enhancing persulfate (PS) catalysis for pollutant degradation. Key catalytic molecular fragments were also identified, providing theoretical insights for further optimizing preparation of BFD-based PS catalysts. The result showed that Fe in BFD-M is primarily Fe3O4 or Fe2O3, while C contains abundant oxygen-containing functional groups and defects. All these catalyze PS to degrade organic pollutants. Surface dispersions of Fe oxides on C substrate increase catalytic site exposure compared to their independent form, while embedding prevents sites loss. Electrostatic potential calculations reveal that oxygen-containing groups, defects, and Fe-O-C structures disrupt the chemical inertness of C substrate, promoting electron transfer and enhancing PS activation. Especially the Fe-O-C exhibit pronounced electron enrichment. The strong interaction between Fe and C increases the formation of C defects, which can enhance PS catalysis and promote Fe3+/Fe2+ cycling, addressing a common limitation of Fe-based catalysts. These findings can provide theoretical guidance for BFD’s innovative applications in pollutants degradation, promoting co-development of steelmaking and environmental remediation.

Ruthenium‐Catalyzed Chemoselective Olefin Transfer Hydrogenation of alpha, beta‐Unsaturated Carbonyl Systems By Using EtOH as Hydrogen Source

AbstractThe use of EtOH as hydrogen donor is remarkably under explored in transfer hydrogenation reactions, even though EtOH represents an appealing hydrogen source. With the cationic ruthenium complex [Ru(PYA)(cymene)]+, 1, containing a N,N‐bidentate amino‐functionalized pyridinium amidate (PYA) ligand as catalyst precursor, we here demonstrate the first example of chemoselective room temperature transfer hydrogenation of the C═C bond in α,β‐unsaturated ketones using EtOH as benign hydrogen source to yield a variety of functionalized ketones. The reaction proceeds under mild conditions with K2CO3 as base and conventiently at room temperature. A broad substrate scope, including various functionalized α,β‐unsaturated carbonyl groups, demonstrates the general applicability of this method. Preliminary mechanistic studies suggest the formation of an alkoxide complex [1]–OEt as an initially formed species, and the requirement for EtOH to induce hydride transfer, suggesting a protic activation of the catalyst.