Bimetallic Oxide Catalysts Research Articles

An effective bimetallic oxide catalyst of RuO2-Co3O4 for alkaline overall water splitting

An effective bimetallic oxide catalyst of RuO2-Co3O4 for alkaline overall water splitting

Synergistic Ti-Fe Oxides on Fishbone-Derived Carbon Sulfonate: Enhanced Styrene Oxidation Catalysis

Fishbone-derived carbon sulfonate, modified through incipient wetness impregnation with titanium tetraisopropoxide and iron nitrate salts, displays catalytic activity in the oxidation of styrene with hydrogen peroxide (H2O2) as an oxidant. This was done to develop a cost-effective, non-toxic, and environmentally friendly bimetallic oxide catalyst, incorporating titanium and iron oxides on mesoporous-derived carbon fishbone to enhance styrene conversion and benzaldehyde selectivity in styrene oxidation using aqueous H2O2. The catalyst, featuring a combination of titanium and iron oxides on the surface of the fishbone-derived carbon sulfonate, demonstrates higher catalytic activity than single oxide catalysts, such as titanium or iron oxides alone. Factors influencing the catalyst's performance are investigated by using FTIR, XRD, XRF, SEM, and BET surface area. The results reveal that the presence of both titanium and iron oxides on the surface of the fishbone-derived carbon sulfonate and the catalyst's surface area creates a synergistic effect, the primary factors affecting its catalytic activity in styrene oxidation using H2O2 as an oxidant.

Hydrogen production and coke resistance characteristic during volatile reforming over Fe2O3–Ce2O3/sludge char catalyst

The development of sludge to green hydrogen is a win-win solution for alleviating the environmental pollution caused by sludge and low-carbon hydrogen production. A series of iron-cerium bimetallic oxide catalysts on sludge char (SC) were prepared for catalytic volatile reforming in this work. The physicochemical properties of the catalysts were adjusted by doping with different metals and changing the proportion. The results showed that 50Fe50Ce/SC possessing the minimum coke deposition rate (12.79 mg h−1·gcat−1) obtained a hydrogen yield of 280.55 ml g−1 from catalytic reforming at 800 °C with a steam-to-carbon ratio of 4:1. Analysis of the catalyst structure and activity suggested that the excellent activity mainly originated from the large number of oxygen vacancies. Oxygen vacancies promote the migration of lattice oxygen inside the catalyst bulk to the surface to react with the coke deposition, while the missing oxygen of the catalyst is replenished by steam, and oxygen vacancies play an important role in the enhancement of the catalyst activity and the elimination of coke deposition. The positive potential of this study in hydrogen production and carbon reduction were assessed. The study could provide new ideas for organic solid waste to generate green hydrogen and the development of efficient and low-cost catalysts.

Development of CeO2–ZrO2 bimetallic oxide catalyst for quinoxaline synthesis

AbstractIn recent years, heterogeneous catalysts have led to environment‐friendly transformations with better yields and reusability. Pd, one of the initial metals employed in heterogeneous organic synthesis, suffered from limitations like its high cost. This justifies the need for development of catalysts with abundant, low‐cost metals, which has been receiving a lot of attention in the scientific community. In this work, a bimetallic oxide catalyst, CeO2–ZrO2, is synthesized by a sol–gel route. The structure and morphology of the catalyst are investigated using X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray analysis, thermogravimetric analysis, Brunauer–Emmett–Teller measurements, and temperature‐programmed desorption. It is utilized for obtaining quinoxaline derivatives at room temperature. 2,3‐Diphenylquinoxaline is obtained via a simple condensation reaction between 1,2‐diaminobenzene and 1,2‐diketones, catalyzed by CeO2(50)–ZrO2(50) with 87% yield in 15 min. Quinoxalines are known for their biological and therapeutic activities; hence, they are essential molecules. The biological activity of the synthesized quinoxaline derivatives has been evaluated against bacterial and fungal strains. © 2023 Society of Chemical Industry.

Mechanism study on a novel Cu/Fe co-catalyzed heterogeneous particle mediated activation of hydrogen peroxide for efficient degradation of cyanides

The degradation of cyanide ions in cyanide containing wastewater is a major challenge in water treatment. This article uses a one-step hydrothermal method to prepare iron copper bimetallic oxide catalysts and applies them for the rapid degradation of cyanide (CN−). The experimental results show that under the optimal conditions, the removal rate of CN− in the bimetallic catalyst/H2O2 system is close to 100 % within 1 h, which is significantly better than the single metal oxide catalyst. Through characterization by SEM-EDS, XRD, XPS, and combined with catalytic performance experimental analysis, it was found that. There is a synergistic effect between Cu and Fe, which can effectively promote the cycling of metal ions and improve the generation efficiency of hydroxyl radicals (HO•) to a certain extent, thereby improving the degradation performance of CN−. In addition, ion chromatography was used to analyze the oxidation products and a possible pathway for CN− degradation was proposed. This provides new insights and ideas for the development of high-performance bimetallic oxide catalysts for cyanide degradation.

Binary Metal-Oxide Active Sites Derived from Cu-Doped MIL-88 with Enhanced Electroactivity for Nitrate Reduction.

Nitrate-to-ammonia electrochemical conversion is important for decreasing water pollution and increasing the production of valuable ammonia. However, achieving high ammonium production without undesirable byproducts is difficult. Cu-doped MIL-88-derived bimetallic oxide catalysts with electrocatalytically active Fe-O-Cu bridges, which have high NO3- adsorption energy and facilitate N-intermediate hydrogenation, are developed for NH4+ production. Cu doping promotes hybridization between the O 2p of NO3- and Fe-Cu 3d, facilitating the adsorption and reduction of NO3- with a low Tafel slope (62.1 mV dec-1) and high ammonia yield (1698.8 μg·h-1·cm-2). The cathode efficiency is stable for seven cycles. Cu adjacent to Fe sites inhibits hydrogen evolution, promotes NO3- adsorption, and decreases the intermediate adsorption energy barrier. This study provides new opportunities for fabricating diverse binary metal oxides with new interfaces as efficient cathode materials for selective electroreduction.

Mn/Co bimetallic MOF-derived hexagonal multilayered oxide catalysts with rich interface defects for propane total oxidation: Characterization, catalytic performance and DFT calculation

Several hexagonal layered Mn/Co oxide catalysts were synthesized from Mn/Co-based metal–organic framework (MOF) precursors. The molar ratio of Mn/Co affects the physicochemical properties of catalysts, further affects their catalytic performance. The Mn/CoOx-3/2 sample with wide interlayer spacing exhibited the highest catalytic activity for total oxidation of propane, with a T90 of 270 °C at 120 L g−1 h−1. Low-temperature reducibility, oxygen mobility, water vapor tolerance, and oxygen defects play the key roles for improving catalytic activity. Oxygen defects were calculated using the density functional theory (DFT). The results show that the doping of Mn on Co oxide is conducive to the formation of oxygen vacancies. Therefore, benefiting from the layered structure and metal-doping for the catalysts, the formation of more abundant interfacial defects can further improve the catalytic performance. This study offers a simple way to synthesize regular layered multi-metal oxide, which can expose abundant interface defects and active sites.

Ruthenium-nickel oxide derived from Ru-coupled Ni metal–organic framework for effective oxygen evolution reaction

Developing Ru-based catalysts with both high activity and stability for the oxygen evolution reaction (OER) is very significant in the water electrolysis technique. Here, a bimetallic metal oxide catalyst (RuO2-NiO) derived from Ru-coupled Ni metal–organic framework (Ni-MOF) by using terephthalic acid as the ligand was successfully synthesized through a facile ultrasonic treatment and subsequent thermal annealing approach; and the effective role of the coupled effect between RuO2 and NiO in stabilizing Ru was found significant in OER catalysis. A relatively small d-band center due to the electronic structure regulation and synergistic effect of the heterostructure was found to cause weakened adsorption of surface oxygen species. Theoretical calculations demonstrated that the electronic modulation between RuO2 and NiO can significantly accelerate the dissociation of water and modulate the chemical adsorption of oxygen intermediates on the catalyst, thereby enhancing the OER activity of the catalyst. The optimized catalyst of RuO2-NiO afforded a current density of 10 mA cm−2 at low overpotentials of 210 mV toward OER, and good catalytic stability, kinetics and efficiency were also discussed. This remarkable catalytic performance can be attributed to the unique sheet-like structure and porous morphology of the catalyst with increased exposure of active sites and the coupling effect between RuO2 and NiO for moderate binding strength to the intermediates. This study showed an effective approach for bimetallic oxide catalyst fabrication and their applications in energy conversion reactions.

Insights into effects of grain boundary engineering in composite metal oxide catalysts for improving catalytic performance

Volatile Organic Compounds (VOCs) have long been a threat to human health. However, designing economical and efficient transition metal composite oxide catalysts for VOCs purification remains a challenge. Herein, this study demonstrates the enormous potential of grain boundary engineering in facilitating VOCs decomposition over ordered mesoporous composite oxide denoted as 3D-MnxCoy (x, y = 1, 3, 5, 7, 9). Specifically, the three-dimensional (3D) Mn7Co1 catalyst shows 100% ethyl acetate removal efficiency for a continuous airflow containing 1000 ppm ethyl acetate over 60000 h−1 space velocity at 160 °C. Mechanism study suggests that the high catalytic performance originates from the lattice distortion caused by the introduction of heteroatoms, along with the size effect of nanopore walls, which leads to the formation of various grain boundaries on the catalyst surface. The presence of grain boundaries facilitates the generation of oxygen vacancies, thus promoting the migration and activation of oxygen species. Furthermore, the near-atmospheric pressure X-ray photoelectron spectroscopy (NAP- XPS) monitoring results reveal that the bimetallic synergy enhanced by grain boundary accelerates the catalytic reaction rate of VOCs through Mn3++Co3+↔Mn4++Co2+ redox cycle. This study may shed light on the great potential of ordered mesoporous bimetallic oxide catalysts in VOCs pollution control.

Coeffect of Co-Mn in bimetallic oxide catalyst for ultrafast electrochemical reduction of nitrate: Insight into ion interaction

Co3O4 has been considered as promising catalysts for electroreduction of nitrate (ERN), which is an emerging tactic to close the nitrogen cycle on earth. However, the nitrate reduction efficiency of Co3O4 is less than satisfactory, which could be enhanced by assistance of Mn element. Herein, we synthesized Co3O4, Mn2O3 and Mn1.5Co1.5O4 nanoparticles for electrodes via a simple sol–gel method using metal nitrates. Moreover, a special electrode 3-Mn/Co was fabricated by physical mixed Co3O4 and Mn2O3. Mn1.5Co1.5O4 and 3-Mn/Co electrodes presented 78.6 % and 64.09 % nitrate removal efficiency after 3 h, 115.46 % and 75.68 % higher than that of Co3O4, proving the existence of Co-Mn coeffect. The optimum Mn1.5Co1.5O4 endures operating parameters experiments of applied potential, level of NO3– concentration, pH value and Cl- concentration and maintains solid stability through ten batches of reaction. Eventually, the ion valence changes of electrodes before and after electrocatalysis verifies that both Co and Mn function in the reaction. The ERN performance variation between electrodes, doped and physically mixed with Mn, and Co3O4 further elucidates that Mn3+ takes major effect in ERN process, while Mn4+ would blocks the electrons transferred to NO3–. In general, a novel process of Co3+/Mn3+- Co2+/Mn4+ reaction cycle in Co and Mn bimetallic and monometallic oxides for ERN performance is proposed as a clue for electrode fabrication.

Synthesis of Vertically Aligned Carbon Nanotube Arrays from Premade Bimetallic Aluminum-Iron Oxide Nanoparticles Monolayer

: Carbon Nanotubes (CNTs) are excellent materials because of their unique physical and chemical properties. Though catalyst nanoparticles preparation from thin film catalysts are common but premade catalysts nanoparticles in liquid phase has control over the size and composition which control the diameter and length of CNTs. Here, we report the synthesis of vertically aligned (VA) CNTs on metal oxide substrates including silicon oxide and stainless-steel using aluminum-iron oxides Al2O3-Fe2O3 nanoparticles monolayer. Oleic acid functionalized Al2O3-Fe2O3 nanoparticles were assembled onto metal oxide substrate as a monolayer using 11-phousnoundecanoic acid (PNDA) linker molecule where phosphonate group bind to the substrate and terminal carboxylic group of PNDA bind to the surface of bimetallic oxide catalysts. Homogenous catalyst nanoparticles distribution from monolayer assembly can reduce the aggregation of catalyst particles which can increases the catalyst lifetime during CNTs growth. Synthesis of VA-CNTs require Al2O3 catalyst support on substrate surface, but our bimetallic Al2O3-Fe2O3 nanoparticles contain both catalyst support (Al2O3) and catalyst (Fe) in the same particle. The successful VA-CNTs synthesis were achieved by chemical vapor deposition (CVD) process using acetylene as carbon precursor in atmospheric pressure. We envision that our catalyst preparation for VA-CNTs growth can be a cost-efficient method for large scale synthesis of CNTs. Further, the VA-CNTs growth on conductive stainless-steel substrate can facilitate the electrochemical application of this hybrid materials for biomolecule sensing and heavy metals detection.

Effective Synergistic Hafnium-Aluminum Bimetallic Oxides catalysts for the Synthesis of 5-Hydroxymethylfurfural from Glucose and Fructose

5-Hydroxymethylfurfural (5-HMF) is considered as a bridge connecting biomass and petrochemical products with excellent application potential and market prospects. In this work, a series of hafnium-aluminum bimetallic oxide (Al-HfOx) catalysts were synthesized with the coprecipitation method, possessing outstanding catalytic effect in the conversion of glucose or fructose to 5-HMF. 5-HMF yield of 49.31% was acquired from glucose in a methyl isobutyl ketone (MIBK)/saturated salt water (SSW) biphasic solvent at 170 ℃ after 2 h. When fructose was the substrate, 5-HMF yield was 74.85% in DMSO at 150 ℃ after 75 min. In addition, the reaction mechanism was speculated that the isomerization process could be promoted by the synergistic effects of aluminum and hafnium species, in which Hf-OH and Al-OH groups, and Hf active sites served as Brønsted and Lewis acidic sites, respectively. After at least four cycles, there was no remarkable wastage in the catalytic activity of Al-HfOx. This paper offers a prospective catalytic strategy for heterogeneous bimetallic oxide catalysts used in the effective conversion of carbohydrates to 5-HMF.

Aquathermolysis of heavy oil using a mixed nickel-oxide/iron-oxide catalyst: Effects induced by crystal phase of iron oxide

Nickel and iron compounds have garnered attention as catalysts for upgrading heavy oil via aquathermolysis. However, research on the performance of bimetallic oxide catalysts in aquathermolysis remains limited. To that end, NiO–Fe2O3 catalysts were prepared in this study using a simple physical mixing method and employed in heavy-oil aquathermolysis to investigate the synergistic relationship between NiO and Fe2O3. The product distributions and quality were systematically analyzed, and an asphaltene upgrading index was introduced to evaluate the coke-inhibiting ability of the catalysts. Interestingly, the crystal structure of Fe2O3 in the NiO–Fe2O3 catalysts remarkably influenced the catalytic performance. Particularly, the NiO/α-Fe2O3 catalyst with highly crystalline α-Fe2O3 considerably prolonged the coke induction period up to ∼30% of residue conversion and induced a high deasphalted oil yield from asphaltenes. Moreover, NiO/α-Fe2O3 improved the product quality by removing impurities (S, N, and O) and increasing the H/C ratio. However, the liquid product distribution remained dependent on the thermal cracking effect, as the NiO–Fe2O3 catalysts did not participate in C–C cleavage. Deuterium tracing was performed to elucidate the hydrogen-transfer mechanism in catalytic aquathermolysis. The formation of deuterium–carbon single bonds from catalytic aquathermolysis was three times higher than that in the absence of the catalyst, confirming that NiO/α-Fe2O3 facilitated hydrogen transfer from water molecules to hydrocarbons during aquathermolysis.

Starch-based porous carbon microsphere composited NiCo2O4 nanoflower as bifunctional electrocatalyst for zinc-air battery

It is significant to explore and design outstanding bifunctional oxygen electrocatalysts to promote the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in zinc–air batteries. Herein, a novel porous carbon microspheres (CMS2) modified by NiCo2O4 nanoflower (CMS2–NiCo2O4) have been prepared as an ORR and OER catalyst. The hierarchical porous structure of CMS provides high conductivity and abundant active sites for ORR, whereas the synergistic effect of NiCo2O4 nanosheets and a small amount of FeZn oxides act as the positive phase for OER. The efficient oxygen catalytic activity is gained by creating a coupling interface between NiCo2O4 and CMS. The optimized CMS2–NiCo2O4 shows a half–wave potential of 0.82 V toward ORR and an overpotential of 392 mV toward OER. Particularly, CMS2–NiCo2O4 also exhibits an excellent peak power density (175.5 mW cm−2) as a catalyst for zinc–air batteries, which is superior to the commercial Pt/C + RuO2 catalyst (120.5 mW cm−2), and it also demonstrates a remarkable stability even after the charge–discharge cycles of 167 h. The prepared CMS2–NiCo2O4 is promising for the application of the bimetallic oxide catalyst for zinc–air battery.

Optimization sulfur doping of electronic structure with metal active center for defect-rich FeCo bimetallic hydroxyl oxide catalysts

Defect engineering is an effective method to tune electronic states, which can provide active sites for electrocatalytic reactions. Herein, a highly efficient sulfur-doped bimetallic hydroxyl oxide (FeCo/Vc-S) has been synthesized by a two-step hydrothermal reaction, which has the rich defective and amorphous phases. The low coordination number of Co in X-ray absorption fine structure (XAFS) analysis further confirms the Co center is the active center, while Fe plays a role in optimizing the electronic structure of active Co species. Meanwhile, abundant oxygen vacancies and metal defects are also found in the material, which greatly enhances the adsorption and desorption efficiency of × OOH. Moreover, density functional theory (DFT) shows that the addition of S atom alters the electron distribution of adjacent metal atoms, thus adjusting the electron distribution of the metal active site. These positive factors endow FeCo/Vc-S with excellent OER electrocatalytic performance, with an overpotential of only 255 mV and Tafel slope is 64.3 mV·dec−1 at a current density of 10 mA cm−2. This study provides a new route for the synthesis of bimetallic hydroxyl oxides, and also provides theoretical design for the identification of active centers and defection-rich catalysts.

Low-temperature dehydrogenation of dodecahydro-N-ethylcarbazole catalyzed by PdCo bimetallic oxide

Liquid organic hydrogen carriers have attracted significant attention for hydrogen storage and transportation and have been extensively investigated. Pd-based noble metal catalysts have been reported as some of the most active catalysts, however, achieving an optimal Pd utilization efficiency and stability remains challenging but significant. Herein, a PdCoOx-based bimetallic oxide catalyst was prepared and applied for the low-temperature dehydrogenation of dodecahydro-N-ethylcarbazole (12H-NECZ) to produce H2, utilizing the following advantages: (1) the activity of Pd was enhanced by introducing Co to form a PdCoOx bimetallic oxide site; (2) the electronic state of the catalyst was tuned based on the interfacial effect between the PdCoOx and Zr-C3N4 supports. Thus, PdCo bimetallic oxide formation improved the electronic transfer rate and the interaction between the support and PdCoOx, thereby enhancing the catalytic dehydrogenation activity. Consequently, 12H-NECZ was completely dehydrogenated with 95.6 % selectivity at 140 °C for 8 h, with only 2.63 wt% Pd loading.

Excellent operating temperature window and H2O/SO2 resistances of Fe-Ce catalyst modified by different sulfation strategies for NH3-SCR reaction.

Expecting to gain an excellent operating temperature window and superior catalytic activity of the catalyst in SCR reaction, the Fe-Ce bimetallic oxide catalyst was firstly prepared and sulfated with two different sulfation strategies by H2SO4. It is interestingly found that both the two sulfation strategies can significantly broaden the operating temperature window of the catalyst. In particular, the SFC and FCS both exhibit superior resistance to H2O + SO2, and the NOx conversion of the SFC even displays no changes in the coexistence of H2O and SO2. The characterization results show that different sulfation strategies can generate amorphous sulfate species rather than bulk sulfate species. Furthermore, more surface-adsorbed oxygen as well as higher contents of Ce3+ and Fe3+ can be obtained on the sulfated catalysts, especially for the SFC catalyst. Meanwhile, different sulfation strategies will progressively enhance the redox ability and amounts of strong acid sites, which will contribute to broadening the operating temperature window for the NH3-SCR reaction. Additionally, different sulfation methods do not change the reaction pathway of catalysts. However, the adsorption of ad-NH3 species and reactivity of ad-NOx species are significantly changed. These lead to the reaction pathway shifts to E-R direct over the SFC and the promotion of E-R and L-H mechanisms over the FCS catalyst.

V-Cu bimetallic oxide supported catalysts for synergistic removal of toluene and NOx from coal-fired flue gas: The crucial role of support

It is a major challenge to achieve effective synergistic reduction of NOx and VOCs in coal-fired flue gas under complex working conditions. In this work, V-Cu bimetallic oxide catalysts with different supports were designed. V1-Cu5 bimetallic oxide supported on TiO2 showed significantly higher activity for simultaneous toluene oxidation and NOx reduction than that supported on ZSM-5, SiO2 and γ-Al2O3. Meanwhile, it exhibited excellent stability and anti-poisoning performance, and could block the formation of toxic polycyclic aromatic hydrocarbons in by-products. Compared with ZSM-5, SiO2 and γ-Al2O3, TiO2 as support was conducive to the formation of abundant acidic sites and oxygen vacancies. In addition, the strong interaction between the metal active sites and TiO2 accelerated the electron transfer from Cu to adsorbed O2, thus promoting the formation of active O2−. This work can provide guidance for the development of catalysts designed for the simultaneous catalytic removal of NOx and VOCs.

Improved redox synthesis of Mn-Co bimetallic oxide catalysts using citric acid and their toluene oxidation activity.

In this work, high-activity cobalt-doped α-MnO2 hybrid materials were prepared using the citric acid oxidation reduction (CR) technique and applied to the catalytic oxidation of toluene. Compared to the traditional processes such as sol-gel, co-precipitation and our previous reported self-driving combustion process, the microstructure of Mn-Co bimetallic oxide catalyst is easier to regulated as well as the dispersion of active phase. Moreover, some accurate characterization techniques such as XRD, H2-TPR, O2-TPD, SEM, TEM, and XPS have been employed, to further illustrate the intrinsic factors for the efficient catalytic oxidation of toluene. It was ultimately found that the CR-Mn10Co1 prepared by citric acid oxidation reduction method could catalyze the oxidation of 90% of toluene at 232 °C, and its excellent catalytic performance was significantly related to its large specific surface area, excellent oxidation reduction ability, and abundant Mn3+ species and oxygen vacancy content. Therefore, citric acid oxidation reduction (CR) provides a convenient and effective route for the efficient and low-cost synthesis of Mn-Co catalysts for removing VOCs.

Ce–Fe bimetallic oxide catalysts for CO catalytic oxidation at a high concentration of SO2

The doping of Fe into the CeO2 lattice played a positive role in enhancing the CO oxidation activity and SO2-poisoning resistance of Ce0.7Fe0.3.