Efficient Oxidation Catalysts Research Articles

Characterization of the Bottlenecks and Pathways for Inhibitor Dissociation from [NiFe] Hydrogenase.

[NiFe] hydrogenases can act as efficient catalysts for hydrogen oxidation and biofuel production. However, some [NiFe] hydrogenases are inhibited by gas molecules present in the environment, such as O2 and CO. One strategy to engineer [NiFe] hydrogenases and achieve O2- and CO-tolerant enzymes is by introducing point mutations to block the access of inhibitors to the catalytic site. In this work, we characterized the unbinding pathways of CO in the complex with the wild-type and 10 different mutants of [NiFe] hydrogenase from Desulfovibrio fructosovorans using τ-random accelerated molecular dynamics (τRAMD) to enhance the sampling of unbinding events. The ranking provided by the relative residence times computed with τRAMD is in agreement with experiments. Extensive data analysis of the simulations revealed that from the two bottlenecks proposed in previous studies for the transit of gas molecules (residues 74 and 122 and residues 74 and 476), only one of them (residues 74 and 122) effectively modulates diffusion and residence times for CO. We also computed pathway probabilities for the unbinding of CO, O2, and H2 from the wild-type [NiFe] hydrogenase, and we observed that while the most probable pathways are the same, the secondary pathways are different. We propose that introducing mutations to block the most probable paths, in combination with mutations to open the main secondary path used by H2, can be a feasible strategy to achieve CO and O2 resistance in the [NiFe] hydrogenase from Desulfovibrio fructosovorans.

3D-interconnected N-doped porous carbon with hierarchical pore structure as a high-efficiency catalyst for H2S oxidation at room temperature

Nitrogen-doped porous carbons (NPCs) have been regarded as an efficient metal-free catalyst for H2S oxidation. However, critical factors affecting their desulfurization ability are still unclear, making it difficult to accurately adjust their desulfurization performance to meet industrial requirements. Herein, a novel 3D-interconnected NPC with hierarchical pore structure was synthesized by one-step “leavening” strategy using rice husk and (NH4)2C2O4 as a carbon source and foaming agent, respectively, for H2S oxidation at room temperature. Pyrolysis temperature is the major factor for physicochemical properties of NPCs, and breakthrough sulfur capacity of the optimal NPC reaches up to 1036.68 mg/g, which can remain stable during three desulfurization-regeneration cycles. Comparative experiment shows that H2S capacity of NPC is 1.8 and 4.0 times those of PC and NC, respectively, revealing the excellent desulfurization performance of NPC. The structure-effect relationships between H2S and NPC reveal that both textural and chemical properties of NPC, especially specific surface area, structural defect, and pyrrolic N, play dominant roles in H2S removal. It is very necessary to balance the relationship between textural performances and pyrrolic N to synthesize optimal NPC catalyst. This work provides a valuable reference for rational design of high-efficiency carbon-based catalysts for persistent desulfurization at room temperature.

Hierarchical Porous N-Doped Carbon Particles Derived from ZIF-8 as Highly Efficient H2S Selective Oxidation Catalysts.

In the selective oxidation of H2S, the catalytic activity over N-doped carbon-based catalysts is significantly influenced by the accessibility of active sites and the mass transfer rates of reactant molecules (e.g., H2S and O2) as well as generated sulfur monomers. Therefore, it is crucial for enhancing the initial performance via the controlled synthesis of carbon-based catalysts with highly exposed active sites and unique porous structures. Herein, we reported on an efficient strategy to synthesize nanosized N-doped carbon particles with hierarchical porous structures by directly pyrolyzing an oversaturated NaCl-encapsulated ZIF-8 precursor mixture. The introduction of NaCl not only serves as a pollution-free template to promote the formation of graphitic carbon layers but also acts as an intercalating agent to guide the derivation of hierarchical porous structures, as well as enhances the amount of active nitrogen species in the catalysts. As a result, the as-prepared H-NC800 catalyst shows excellent H2S selective oxidation performance (sulfur formation rate is 794 gsulfur·kgcat-1·h-1), good stability (>80 h), and antiwater vapor properties. The characterization results and DFT calculations indicate the crucial role of pyridinic N in the adsorbing and activating reactant molecules (H2S, O2). Furthermore, nanoscale N-doped carbon particles accelerated the rapid transport of generated sulfur monomers under a hierarchical porous structure. This investigation introduces a distinctive strategy for synthesizing ZIF-8-derived N-doped carbon nanosized with a hierarchical porous structure, while its efficient and stable H2S selective oxidation performance highlights significant potential for practical implementation in the industrial desulfurization process.

Catecholase activity assessment of In-Situ copper complexes derived from a novel Schiff base ligand

This study focuses on the synthesis, characterization, and evaluation of catecholase activity in a series of in-situ copper complexes derived from a novel Schiff base ligand, 2,2′{(methylimino)bis[propanediylnitrilo(Z)methylylidene]}bis(5-methoxyphenol) (MBPM). The ligand MBPM and its complex [Cu(MBPM)] were successfully synthesized and characterized using various analytical techniques, including X-ray crystallography, IR spectroscopy, and 1H NMR spectroscopy. Subsequently, we investigated the catalytic activity of these complexes in the oxidation of catechol to o-quinone. The results revealed a remarkable difference in catecholase activity between the Schiff base ligand-derived complex, [Cu(MBPM)], and in-situ copper complexes. The [Cu(MBPM)] complex exhibited significantly higher catalytic activity, underscoring its potential as an efficient catalyst for catechol oxidation. This enhanced activity can be attributed to structural differences and the presence of multiple active sites within the [Cu(MBPM)] complex.

Constructing Efficient CuAg Nanoalloys on Ce0.90In0.10Oδ for Methanol Deep Oxidation Catalysis at Low Temperature.

So far, it is still extremely challenging to develop an efficient catalyst for deep oxidation of methanol at low temperature. Herein, we report the construction of the highly dispersed CuAg alloy on the surface of Ce0.90In0.10Oδ nanorods support for catalyzing methanol deep oxidation. The composition, structure and properties of catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectroscopy and X-ray photoelectron spectroscopy (XPS). The results show that the CuxAg100-x/Ce0.90In0.10Oδ alloy catalysts exhibit superior catalytic activity and stability compared to pure Ag/Ce0.90In0.10Oδ, with the highest activity observed for Cu40Ag60/Ce0.90In0.10Oδ, accompanied by the light-off temperature (T50) and full conversion temperature (T90) of 115 and 145 °C, respectively. This is attributed to the synergistic effect of CuAg alloy, which results in electron transfer, generating more Ag0, and enhanced interaction between CuAg alloy and the support, leading to increased Ce3+ content and higher oxygen vacancy concentration. This work successfully applies CuAg alloy catalysts in thermo-catalytic reaction, offering promising prospects for CuAg alloy catalysts in the methanol deep oxidation.

Light-induced phase transformation to two-dimensional amorphous spinel CoAlOx nanosheets as a tandem photothermal catalyst for efficient and durable toluene oxidation

Low temperature fabrication of spinel oxides and development of efficient and durable toluene photothermal catalysts remain challenging. Herein, two-dimensional amorphous spinel CoAlOx nanosheets (CoAl-LDH-L2) have been fabricated via a light-induced phase transformation strategy using intense photooxidation. Light-induced decomposition and phase transformation process have been used to elucidate the growth mechanism. The CoAl-LDH-L2 exhibits improved toluene adsorption and photothermal conversion, with the highest photothermal catalytic toluene conversion (∼100 % at 500 ppm) at 90 °C, outperforming most previously reported catalysts. Irradiation with mild external heating significantly increases the mineralization rate (∼90 %) and improves the long-term and cycling stability (∼5% losses within 39 h) relative to that under single-light-driven conditions. In-situ DRIFT spectroscopy was also performed for revealing the “tandem photothermal catalysis” mechanism for toluene conversion. This work offers a novel strategy for developing spinel oxides as low-temperature photothermal catalyst in a green and sustainable way.

Correction to “Thermoresponsive Polymeric Nanoparticles as Efficient Pickering Interfacial Catalysts for Selective Oxidation of Sulfides”

Correction to “Thermoresponsive Polymeric Nanoparticles as Efficient Pickering Interfacial Catalysts for Selective Oxidation of Sulfides”

Cellulose conversion to 5-hydroxymethylfurfural via a simple and efficient phosphate-doped hafnium oxide catalyst

The efficient catalytic conversion of cellulose to 5-hydroxymethylfurfural (HMF) can provide a valuable reference for the high-value utilization of biomass. In this work, a series of simple phosphate-doped hafnium oxide catalysts (x-P-HfO2) were prepared, and their physicochemical properties were analyzed by ICP-OES, XRD, XPS, FTIR, SEM-EDX, N2 adsorption-desorption isotherms, NH3-TPD and Py-FTIR characterizes. Detailed evaluation of the reaction conditions demonstrated the ideal catalytic performance of the x-P-HfO2 catalysts, and the HMF yield from cellulose reached a satisfactory 61% in the water(NaCl)/tetrahydrofuran biphasic reaction system. Based on the captured intermediates and detected by-products, possible catalytic pathways are summarized. Meanwhile, the hydrothermal stability of the catalyst was also investigated, and the reason for its performance degradation after five cycles was determined to be the loss of useful Brønsted active sites. In addition, the effects of the phosphating and sulfating modification approaches on the catalyst activity were also compared, verifying that the introduction of phosphate is more conducive to the catalyst expressing high activity for the formation of HMF from cellulose.

Construction of Co3S4/MoS2 p-p heterojunction as an efficient catalyst for water splitting and electrochemical oxidation of organic molecules

Electrolysis of wastewater containing urea or small organic molecules while obtaining hydrogen energy is a promising strategy for realizing energy acquisition and environmental protection. Construction of semiconductor heterojunctions to regulate the transfer of interfacial electrons has been regarded as an efficient approach to improve the electrocatalytic performance of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) for the materials, and obtain the bifunctional electrocatalysts aiming to construct a water splitting cell using one non-precious metal material. Herein, a bifunctional Co3S4/MoS2 electrocatalyst with a p-p heterojunction and hollow structure has been successfully prepared through the precipitation-hydrothermal method, which presents the high bifunctional electrocatalytic performance due to the formed path of electron transfer in the heterojunction interface being favorable for OH- adsorption. The accelerated electron transfer in heterojunction interfaces endows Co3S4/MoS2 presenting the superior electrocatalytic performance including OER, urea oxidation reaction (UOR) and oxygen evolution reaction in lactic acid solution (OER-LA). At 50 mA cm−2, the voltages of HER, OER, UOR and OER-LA are −0.123, 1.511, 1.400, 1.440 V vs. RHE, respectively. In a two-electrode electrolytic cell using Co3S4/MoS2 as anode and cathode displays the outstanding electrocatalytic performance in 1 M KOH, 1 M KOH containing 0.5 M urea, and 1 M KOH containing 0.5 M lactic acid electrolytes, superior to the most reported materials. This research provides a strategy for the construction of advanced bifunctional electrocatalysts using metal sulfides to form heterojunction for realizing the high bifunctional catalytic activities in hydrogen production and organic molecule decontamination.

Interface Engineering of Electrocatalysts for Efficient and Selective Oxygen Evolution in Alkaline/Seawater

Electrochemical water splitting is regarded as an effective technology for producing green hydrogen, which is crucial for addressing energy and environmental challenges. In particular, direct seawater splitting offers significant economic and environmental advantages. However, its efficiency is hindered by the high overpotential required for the oxygen evolution reaction (OER) and the competition from chloride oxidation. This review highlights the potential of interface engineering to overcome these limitations and develop efficient OER electrocatalysts. We comprehensively explore recent advancements in interface engineering for OER in both alkaline and seawater environments. We begin by introducing the mechanisms of freshwater and seawater electrolysis, emphasizing key considerations for OER catalyst design. Subsequently, we review the recent progress made in various interface engineering strategies, analyzing their impact on OER performance in both electrolytes. Finally, we outline promising future directions for developing efficient seawater oxidation catalysts through interface engineering.

One-Step Hydrothermal/Solvothermal Preparation of Pt/TiO2: An Efficient Catalyst for Biobutanol Oxidation at Room Temperature.

The selective oxidation of biobutanol to prepare butyric acid is an important conversion process, but the preparation of low-temperature and efficient catalysts for butanol oxidation is currently a bottleneck problem. In this work, we prepared Pt-TiO2 catalysts with different Pt particle sizes using a simple one-step hydrothermal/solvothermal method. Transmission electron microscopy and X-ray diffraction results showed that the average size of the Pt particles ranged from 1.1 nm to 8.7 nm. Among them, Pt-TiO2 with an average particle size of 3.6 nm exhibited the best catalytic performance for biobutanol. It was capable of almost completely converting butanol, even at room temperature (30 °C), with a 98.9% biobutanol conversion, 98.4% butyric acid selectivity, and a turnover frequency (TOF) of 36 h-1. Increasing the reaction temperature to 80 and 90 °C, the corresponding TOFs increased rapidly to 355 and 619 h-1. The relationship between the electronic structure of Pt and its oxidative performance suggests that the synergistic effect of the dual sites, Pt0 and Pt2+, could be the primary factor contributing to its elevated reactivity.

Controlled synthesis of Co3O4@CoP heterostructured nanoarrays as efficient electrocatalysts in alkaline seawater and urea

How to prepare clean energy has always been a problem to be solved by the modern green chemical industry. Compared with the electrolysis of water to produce hydrogen, electrolysis of seawater for raw material requirements are lower and more widely used. However, the lacks of maturity of the technology, the high cost and the generation of harmful gases such as chlorine in the electrocatalytic process have hindered the development of this process. This study demonstrates a construction of heterogeneous structure based on Co ions as an efficient multifunctional catalyst for overall seawater splitting and urea oxidation. This hybrid structure can combine nanosheets and nanowires, thus exposing the catalyst to more active sites and shortening the ion diffusion path. Comparing the hybrid structure with the single structure, Co3O4@CoP exhibits excellent multifunctional catalytic activity in alkaline seawater and urea. In the oxygen evolution reaction, the working potential is only 1.60 V and 1.70 V at a current density of 50 mA/cm2 and 100 mA/cm2. And in the hydrogen evolution reaction, the working potential was only −0.16 V at a current density of −10 mA/cm2, demonstrating excellent bifunctional activity. On this basis, the catalyst also demonstrated excellent activity for urea oxidation reaction in alkaline environment, with an operating potential of only 1.28 V at a current density of 10 mA/cm2. And the durability of this catalyst is good, it can keep 5 mA/cm2 for 12 h under the constant voltage of 1.45 V, but the initial potential falls off too fast, and there is a decline in performance, which is closely related to the corrosion of Cl- present in seawater. It was shown by density functional theory (DFT) that hierarchical nanostructures can increase the transfer rate of reaction intermediates and the water adsorption energy. At the end of this study, by comparing single nanostructures with hybrid nanostructures, it can be reasonably conjectured that the accompanying increase in the number the heterostructure is resistant to Cl- corrosion in seawater.

Unraveling the Oxygen Vacancy Site Mechanism of a Self-Assembly Hybrid Catalyst for Efficient Alkaline Water Oxidation

Unraveling the Oxygen Vacancy Site Mechanism of a Self-Assembly Hybrid Catalyst for Efficient Alkaline Water Oxidation

ZIF-67-derived Co@NC as an efficient catalyst for magnesium sulfite oxidation in the flue gas desulfurization process

Magnesium desulfurization is a wet flue gas desulfurization (WFGD) technology widely used in China, however, the low oxidation rate of magnesium sulfite (MgSO3), a byproduct of WFGD, causes the subsequent oxidation and crystallization process to require amount energy. Here, we prepared a cobalt-based nitrogen-doped porous carbon catalyst (Co@NC) using ZIF-67 as a precursor for the efficient catalytic oxidation of MgSO3 generated during magnesium desulfurization. The performance of Co@NC catalysts obtained at an optimal calcination temperature of 650 °C showed that the catalysts with oxidation rates up to 0.1332 mmol·L−1·s−1 of MgSO3 were considerably better than those previously studied, which outperformed the catalysts described in earlier research by a considerable margin. Further studies revealed that the Co@NC’s exceptional catalytic activity was attributed to both its special porous structure and the exposed active Co sites in the organic skeleton. The uniformly dispersed Co species act as the active sites of the Co@NC that can be fully contacted with the reactant. The presence of 0.5 g·L−1 Co@NC increases the MgSO3 oxidation rate by about 14 times compared to the noncatalytic benchmark. A practical tactic is furnished by this research for energy saving and emission reduction in the WFGD process, especially for the efficient oxidation and resource conversion of the by-product MgSO3.

Constructing Efficient CuO-Based CO Oxidation Catalysts with Large Specific Surface Area Mesoporous CeO2 Nanosphere Support.

CeO2 is an outstanding support commonly used for the CuO-based CO oxidation catalysts due to its excellent redox property and oxygen storage-release property. However, the inherently small specific surface area of CeO2 support restricts the further enhancement of its catalytic performance. In this work, the novel mesoporous CeO2 nanosphere with a large specific surface area (~190.4 m2/g) was facilely synthesized by the improved hydrothermal method. The large specific surface area of mesoporous CeO2 nanosphere could be successfully maintained even at high temperatures up to 500 °C, exhibiting excellent thermal stability. Then, a series of CuO-based CO oxidation catalysts were prepared with the mesoporous CeO2 nanosphere as the support. The large surface area of the mesoporous CeO2 nanosphere support could greatly promote the dispersion of CuO active sites. The effects of the CuO loading amount, the calcination temperature, mesostructure, and redox property on the performances of CO oxidation were systematically investigated. It was found that high Cu+ concentration and lattice oxygen content in mesoporous CuO/CeO2 nanosphere catalysts greatly contributed to enhancing the performances of CO oxidation. Therefore, the present mesoporous CeO2 nanosphere with its large specific surface area was considered a promising support for advanced CO oxidation and even other industrial catalysts.

Development of Molybdenum oxide Promoted CeO2−SiO2 Mixed‐oxide Catalyst for Efficient Catalytic Oxidation of Benzylamine to N‐Benzylidenebenzylamine

AbstractThis study explores a rational synthesis of a molybdenum‐promoted Ce−Si mixed oxide catalyst (MoO3/CeO2−SiO2) to regulate synergies between MoO3 and SiO2 dopant on CeO2, achieving high selectivity in solvent‐free catalytic oxidative coupling of amines to imines using molecular O2 as the oxidant. Comparative efficiency tests were conducted with bare CeO2, CeO2−SiO2, and MoO3/CeO2 catalysts. Characterization techniques, including XRD, Raman spectroscopy, N2‐adsorption‐desorption analysis, FTIR, NH3−TPD, TEM, and XPS, were employed to assess textural properties, acidic features, promoter and dopant dispersion in CeO2 lattice, and oxygen defects. Mo/Ce−Si catalyst exhibited superior acidic sites and a higher concentration of Ce3+ ions (Iu/ITotal), indicating increased oxygen vacancies. This catalyst demonstrated exceptional performance in the oxidative coupling of benzylamine, providing higher conversion and selectivity to the corresponding imine. Remarkably, the Mo/Ce−Si catalyst maintained consistent performance over five recycling runs. The catalyst also proved effective for the selective oxidative coupling of various amine substrates with diverse steric and electronic properties. Experimental results confirmed a plausible reaction mechanism within the concise catalyst design.

Light-induced in-situ transformation from MOF to construct heterostructured Co3O4/Co catalyst for efficient photothermal catalytic oxidation

The construction of hybrid nanocatalysts with enhanced active surfaces/interfaces is crucial for the catalytic oxidative removal of volatile organic compounds (VOCs). In this study, we report an in-situ conversion approach to synthesize a heterostructured Co3O4/Co catalyst (Co@NC-0.5) for efficient photothermal catalytic oxidation of acetone. The catalysts were prepared by pyrolyzing a mixture of ZIF-67 and melamine. The exposed cobalt species underwent in-situ oxidation to form a Co3O4/Co heterostructure under photothermal conditions. This unique catalyst structure exhibited over 90% conversion within 16 minutes under full solar spectrum irradiation and excellent reusability with continuous maintenance of 100% acetone conversion rate after nine cycles performance tests. Notably, its specific mass activity under thermocatalytic conditions was 2.13 times higher than that of Co3O4. Our work provides a facile and effective strategy for developing highly active and durable non-precious metal catalysts suitable for various photothermal catalytic reactions.

Highly Efficient Ce and Co Codoped OMS-2 Catalyst for NO Oxidation

Highly Efficient Ce and Co Codoped OMS-2 Catalyst for NO Oxidation

Hydrophobic modification of zeolite-supported platinum catalysts for complete oxidation of toluene

Zeolite-supported noble metal nanoparticles have been reported as active catalysts for complete oxidation of volatile organic compounds (VOCs) due to the combination of advantages of zeolite supports and noble metal species, where introducing more Al species (reduction of SiO2/Al2O3 ratios, SAR) and increasing hydrophobicity for zeolite supports are favorable for the complete oxidation of VOCs. Unfortunately, introduction of more Al species in the zeolite frameworks normally reduces the hydrophobicity of zeolite crystals. To overcome this problem, we rationally synthesize hydrophobic zeolites with low SAR by anchoring methyl group, exhibiting exceptionally catalytic performances in the complete oxidation of toluene at very low temperature (T90 at 144 °C) after loading Pt species (1 wt%). Characterizations of the catalysts show a vital role of hydrophobic zeolites for adsorption of more toluene and fast desorption of water. The strategy for preparation of hydrophobic zeolite-supported noble metal catalysts might offer an alternative way to develop highly efficient heterogeneous catalysts for the complete oxidation of VOCs in the future.

H2 production based on a ternary mixture of commercial CuO-NiO-TiO2 in a solar pilot plant

Glycerol is a by-product in biodiesel production (in the range of g·L−1), so its photoreforming by photocatalysis is a way of valorising it. TiO2 in photocatalysis has been widely studied, although its efficiency is limited by the high energy band gap, and the electron-hole recombination. Its combination with different semiconductors should improve charge separation, extending also the absorption from UV to visible light. Cu and Ni oxides are two of the most efficient low-cost transition metal oxide catalysts. Experiments were carried out in a 25 L pilot plant connected to a compound parabolic solar collector. Different combinations of the three semiconductors, based on the concentration of each metal on TiO2 (Me, 5%, 7.2% and 10%) were evaluated. Evonik P25-TiO2, CuO and NiO were combined by mechanical mixing. Hydrogen was quantified by a micro gas chromatograph, and copper and nickel leaching by ICP-MS. The best hydrogen production (0.060 mMol kJ−1) was attained with a proportion of 10:1 of TiO2:MeO, that corresponds to a total metal concentration of 7.2 wt%, being Cu and Ni in the same proportion. Metal content in solution increased as the reaction progressed, but Ni lixiviation of <0.012 mg L−1 was not significant. Significant Cu leaching (>1 mg L−1) was observed. This article presents novel results, in a solar pilot plant, for determining which ternary mixture can give better results, as well as metal leaching into water. Handling relevant volume of water in anoxic conditions can help to understand the application of this technology for the production of hydrogen.