Fe Catalyst Research Articles

Controlled synthesis of NO in an atmospheric pressure plasma by suppressing NO destruction channels by plasma catalysis

NO synthesis using plasma catalysis is analyzed in a parallel-plate atmospheric pressure RF plasma from N2/O2 admixed to helium exposed to Fe and Pt catalysts on a SiO2 support. The NO x species are measured by Fourier-transform infrared spectroscopy in a multi-pass cell. The trends in species densities can be well explained by air chemistry reactions, where NO’s progressive oxidation occurs with increasing oxygen admixture and ozone generation. The sequence can be controlled by the state of the surface that preferentially quenches O3 and allows for an optimum NO production. The maximum production of NO is found at 70% N2/(N2+O2) mixture ratio at 120 ∘C using sandblasted glass, with a conversion rate of 0.085%.

Regulating the Electronic Synergy of Asymmetric Atomic Fe Sites with Adjacent Defects for Boosting Activity and Durability toward Oxygen Reduction

AbstractThe oxygen reduction reaction (ORR) plays a fundamental role in sustainable energy technologies. However, the creation of non‐precious metal electrocatalysts with high ORR activity and durability under all pH conditions is of great significance but remains challenging. Herein, the aim is to overcome this challenge by creating a Fe single atom catalyst on a 2D defect‐containing nitrogen‐doped carbon support (Fe1/DNC) via a microenvironment engineering strategy. Microkinetic modeling reveals that FeN4(OH) moieties are the real active sites under reaction conditions. Due to the synergistic promotion effect of denser accessible FeN4(OH) moieties and defect‐induced electronic properties, Fe1/DNC catalyst achieves extraordinary ORR activity under alkaline, acidic, and neutral conditions, with half‐wave potentials of 0.95, 0.82, and 0.70 V, respectively. Moreover, a negligible performance decay is observed with this Fe catalyst in stability and methanol tolerance tests. Zn‐air battery employing Fe1/DNC delivers remarkable peak power density and long‐term operational durability. Theoretical analysis provides compelling evidence that the defects adjacent to FeN4(OH) moieties can endow an inductive effect to reshape electronic properties to balance the OOH* formation and OH* reduction. This work offers insight into the regulation of asymmetric coordination structure and electronic properties of metal sites for boosting electrocatalytic activity and stability.

Synergistic Effects of Silica-Supported Iron-Cobalt Catalysts for CO2 Reduction to Prebiotic Organics.

To test the ability of geochemical surfaces in serpentinizing hydrothermal systems to catalyze reactions from which metabolism arose, we investigated H2-dependent CO2 reduction toward metabolic intermediates over silica-supported Co-Fe catalysts. Supported catalysts converted CO2 to various products at 180 °C and 2.0 MPa. The liquid product phase included formate, acetate, and ethanol, while the gaseous product phase consisted of CH4, CO, methanol, and C2-C7 linear hydrocarbons. The 1/1 ratio CoFe alloy with the same composition as the natural mineral wairauite yielded the highest concentrations of formate (6.0 mM) and acetate (0.8 mM), which are key intermediates in the acetyl-coenzyme A (acetyl-CoA) pathway of CO2 fixation. While Co-rich catalysts were proficient at hydrogenation, yielding mostly CH4, Fe-rich catalysts favored the formation of CO and methanol. Mechanistic studies indicated intermediate hydrogenation and C-C coupling activities of alloyed CoFe, in contrast to physical mixtures of both metals. Co in the active site of Co-Fe catalysts performed a similar reaction as tetrapyrrole-coordinated Co in the corrinoid iron-sulfur (CoFeS) methyl transferase in the acetyl-CoA pathway. In a temperature range characteristic for deeper regions of serpentinizing systems, oxygenate product formation was favored at lower, more biocompatible temperatures.

Synergism of surface Co-rich activated carbon-supported bimetallic Co:Fe catalysts for Fischer-Tropsch synthesis

ABSTRACT The present study explores the remarkable potential of activated carbon-supported cobalt-rich bimetallic catalysts (Co:Fe) in Fischer-Tropsch (FT) synthesis. The H2/CO ratio of the syngas was maintained at 1 to simulate biomass gasification. The temperature, pressure, and GHSV were maintained at 240°C, 20 bar, and 20 mL g.cat−1 min−1, respectively. Totally five combinations of mono- and bimetallic catalysts were synthesized by sequential impregnation of Fe followed by Co, offering a novel and facile approach. The characterization studies revealed the Co-rich surface of the bimetallic catalysts with Co3O4 as an active metal species. The FT activity tests revealed the superior performance of the bimetallic catalysts than their monometallic counterparts. The selectivity to C5+ compounds increased with increase in Co content while the CO conversion increased up to 5% Fe content and then decreased further. The maximum CO conversion (67.4%) and C5+ yield (47.6%) were observed for 15Co5Fe/AC. The study provides a unique perspective on the advancement of C5+ fuel production in Fischer-Tropsch synthesis, achieved through the synergy of FTS-active cobalt and WGS-active iron.

Unlocking Syngas Synthesis from the Catalytic Gasification of Lignocellulose Pinewood: Catalytic and Pressure Insights.

Modern technologies transform biomass into commodity chemicals, biofuels, and solid charcoal, making it appear as a renewable resource rather than organic waste. The effectiveness of Mo, Fe, Co, and Ni metal catalysts was investigated during the gasification of lignocellulosic pinewood. The primary goal was to compare the performance of iron and nickel catalysts in the low- and high-pressure production of syngas from pinewood. This is the first study that has reported high-pressure gasification of pinewood without the use of an external gasifying agent, producing syngas containing hydrogen, carbon monoxide, and carbon dioxide along with considerable amounts of methane with or without a catalyst. Also, the same gasification at low pressures was compared. In this study, the iron catalyst produces syngas more efficiently at higher pressure and 800 °C, and contains 43 mol % H2, 22 mol % CO2, 26 mol % CH4, and 8 mol % CO in comparison to the nickel catalyst. High pressure produces a large amount of methane too. The nickel catalyst produces higher syngas at low pressure and 850 °C, and contains 55 mol % H2, 9 mol % CO2, 5 mol % CH4, and 30 mol % CO. Low-pressure gasification produces less amounts of CH4 and CO2. Also, the H2/CO ratio is ∼1.81 using the nickel catalyst at low pressures, which is good for utilizing syngas as a feedstock. These results highlight the importance of catalyst selection, reactor configuration, and operating circumstances in adjusting gasification product composition. The study's findings provide information about optimizing syngas production from pinewood, which is critical for the development of sustainable and efficient energy conversion technologies.

Inter-site structural heterogeneity induction of single atom Fe catalysts for robust oxygen reduction

Metal-nitrogen-carbon catalysts with hierarchically dispersed porosity are deemed as efficient geometry for oxygen reduction reaction (ORR). However, catalytic performance determined by individual and interacting sites originating from structural heterogeneity is particularly elusive and yet remains to be understood. Here, an efficient hierarchically porous Fe single atom catalyst (Fe SAs-HP) is prepared with Fe atoms densely resided at micropores and mesopores. Fe SAs-HP exhibits robust ORR performance with half-wave potential of 0.94 V and turnover frequency of 5.99 e−1s−1site−1 at 0.80 V. Theoretical simulations unravel a structural heterogeneity induced optimization, where mesoporous Fe-N4 acts as real active centers as a result of long-range electron regulation by adjacent microporous sites, facilitating O2 activation and desorption of key intermediate *OH. Multilevel operando characterization results identify active Fe sites undergo a dynamic evolution from basic Fe-N4 to active Fe-N3 under working conditions. Our findings reveal the structural origin of enhanced intrinsic activity for hierarchically porous Fe-N4 sites.

Enhancing Ammonia Synthesis on Co3Mo3N via Metal Support Interactions on a Single‐crystalline MgO Support

AbstractCo3Mo3N has been reported to have activity for the synthesis of ammonia surpassing that of industrial Fe catalysts under certain conditions. However, so far the research has largely focused on unsupported Co3Mo3N. We report a comprehensive study on the catalytic activity of Co3Mo3N when supported on two distinct MgO substrates. Our findings reveal that the method of MgO preparation plays a crucial role in influencing surface basicity. Remarkably, Co3Mo3N supported on single‐crystalline MgO demonstrates significantly enhanced catalytic activity, achieving a 162.0 mmol g−1metal h−1 rate. This surpasses the performance on commercial MgO support (41.2 mmol g−1metal h−1) and unsupported Co3Mo3N (15.0 mmol g−1metal h−1). While kinetic analyses show no substantial differences between the two supported catalysts, spectroscopic studies employing CO2 and N2 temperature‐programmed desorption (TPD) reveal a richer array of basic sites and adsorption/desorption phenomena on the single‐crystalline MgO support. These catalysts exhibit exceptional stability. The drastically reduced Co/Mo loading amounts in comparison to the bulk form, make the commercialization of Co3Mo3N catalysts more practical.

Ultrasound Effect on the Hydrogen Peroxide Oxidation of Corn Starch, Molecular Structure, and Functional Properties of Obtained Starch Derivatives

AbstractThis study aims to determine the effect of ultrasound on the oxidation process of starch, molecular structure, and its functional properties. Corn starch is oxidized by hydrogen peroxide (with Cu(II) or Fe(II) ions as catalysts) in the ultrasound field. Changes in starch structure are identified based on determinations of the carboxyl, carbonyl groups, copper, iron content, molecular characterization by GPC, crystallinity, gelatinization characteristics, and surface area. Functional properties are determined based on analysis of color parameters, water binding capacity, solubility in water, and pasting characteristics. It is found that the effectiveness of the starch oxidation under ultrasound is affected by the presence and type of catalysts. The content of metal incorporated into starch during oxidation is approximately 15% lower when an ultrasound treatment is applied. When starch oxidation is assisted with ultrasound, the metal incorporation preferentially occurs in the pores and holes of the grain. Starches oxidized in the presence of Fe(II) and Cu(II) catalysts can be successfully used not only as thickeners in food industry but also as metal carriers in many industries.

Catalyst Selection over an Electrochemical Reductive Coupling Reaction toward Direct Electrosynthesis of Oxime from NOx and Aldehyde.

Aqueous electrochemical coupling reactions, which enable the green synthesis of complex organic compounds, will be a crucial tool in synthetic chemistry. However, a lack of informed approaches for screening suitable catalysts is a major obstacle to its development. Here, we propose a pioneering electrochemical reductive coupling reaction toward direct electrosynthesis of oxime from NOx and aldehyde. Through integrating experimental and theoretical methods, we screen out the optimal catalyst, i.e., metal Fe catalyst, that facilitates the enrichment and C-N coupling of key reaction intermediates, all leading to high yields (e.g., ∼99% yield of benzaldoxime) for the direct electrosynthesis of oxime over Fe. With a divided flow reactor, we achieve a high benzaldoxime production of 22.8 g h-1 gcat-1 in ∼94% isolated yield. This work not only paves the way to the industrial mass production of oxime via electrosynthesis but also offers references for the catalyst selection of other electrochemical coupling reactions.

Catalytic Reduction of Cyanide to Ammonia and Methane at a Mononuclear Fe Site.

Nitrogenase enzymes catalyze nitrogen reduction (N2R) to ammonia and also the reduction of non-native substrates, including the 7H+/6e- reduction of cyanide to CH4 and NH3. CN- and N2 are isoelectronic, and it is hence fascinating to compare the mechanisms of synthetic Fe catalysts capable of both CN- and N2 reduction. Here, we describe the catalytic reduction of CN- to NH3 and CH4 by a highly selective (P3Si)Fe(CN) catalyst (P3Si represents a tris(phosphine)silyl ligand). Catalysis is driven in the presence of excess acid ([Ph2NH2]OTf) and reductant ((C6H6)2Cr), with turnover as high as 73 demonstrated. This catalyst system is also modestly competent for N2R and structurally related to other tris(phosphine)Fe-based N2R catalysts. The choice of catalyst and reductant is important to observe high yields. Mechanistic studies elucidate several intermediates of CN- reduction, including iron isocyanides (P3SiFeCNH+/0) and terminal iron aminocarbynes (P3SiFeCNH2+/0). Aminocarbynes are isoelectronic to iron hydrazidos (Fe═N-NH2+/0), which have been invoked as selectivity-determining intermediates of N2R (NH3 versus N2H4 products). For the present CN- reduction catalysis, reduction of aminocarbyne P3SiFeCNH2+ is proposed to be rate but not selectivity contributing. Instead, by comparison with the reactivity of a methylated aminocarbyne analogue (P3SiFeCNMe2), and associated computational studies, formation of a Fischer carbene (P3SiFeC(H)(NH2)+) intermediate that is on path for either CH4 and NH3 (6 e-) or CH3NH2 (4 e-) products is proposed. From this carbene intermediate, pathways to the observed CH4 and NH3 products (distinct from CH3NH2 formation) are considered to compare and contrast the (likely) mechanism/s of CN- and N2 reduction.

Low-cost Co–Al spinel and M–Co–Al (M = Fe and Ce) catalysts for selective catalytic reduction of NOx with NH3

Low-cost Co–Al spinel and M–Co–Al (M = Fe and Ce) catalysts for selective catalytic reduction of NOx with NH3

Highly Dispersed K- and Pd-Comodified Fe Catalyst for CO2 Hydrogenation to Higher Alcohols

Highly Dispersed K- and Pd-Comodified Fe Catalyst for CO₂ Hydrogenation to Higher Alcohols

Synergy between Fe and Mo single atom catalysts for ammonia electrosynthesis

Electrochemical nitrate to ammonia conversion provides an eco-friendly route for a highly valued product. However, nitrite intermediate formation and hydrogen evolution competition hinder full conversion. Here, we implement a Fe-Mo dual single-atom catalyst where the two metals work in tandem to achieve nitrate to ammonia conversion with excellent activity and stability, an ammonia yield rate of up to 13.56 mg cm−2 h−1 and a Faradaic efficiency up to 94%. In-situ Raman and Fourier-transform infrared spectroscopy confirms nitrite as the intermediate bound to metal sites. Time-dependent detection of products and DFT calculations support a tandem mechanism: the Mo single atoms are the preferred sites for the conversion of nitrate to nitrite, while the Fe single atoms catalyze the further conversion of nitrite to ammonia. This discovery paves the way for energy-relevant transformations using bimetallic single-atom catalysts.

Simultaneous Removal of Gas-Phase Pollutants CO and NO Using Ni-Fe Bimetallic Oxides Catalyst

Many studies have been conducted on methods to remove air pollutants. Among them, a representative commercial technology for reducing nitrogen oxides (NO<sub>X</sub>) is selective catalytic reduction (SCR) using NH<sub>3</sub> as a reductant. However, the NH<sub>3</sub>-SCR technology has problems, such as the need for additional NH<sub>3</sub> gas (Active-SCR), the fact that unreacted NH<sub>3</sub> (slipped-NH<sub>3</sub>) in the reaction process can be re-oxidized to NO<sub>X</sub>, and the facility system cost according to the added NH<sub>3</sub> gas. In order to solve these problems, CO gas that is naturally generated in industrial processes can be used, and NO and CO can be removed at the same time using passive-SCR technology that does not require a separate injection of a reductant. In this study, transition metals Ni and Fe were used as catalytic materials to replace expensive precious metals. The results confirmed that both NO<sub>X</sub> and CO removal efficiencies were about 90% or more in the catalyst with combined Ni-Fe, compared to the single catalyst. The addition of Ni to the Fe catalyst increased the catalytic reducing power, which also affected the increase in acid sites. Therefore, it is expected that this catalyst can simultaneously remove NO and CO without the use of NH<sub>3</sub> gas. These results could be explained through XRD, FT-IR, TEM, BET, H<sub>2</sub>-TPR and CO-TPD analyses, and compared to single catalysts, it was confirmed that the catalyst had higher low-temperature desorption ability for CO as a reductant and reducing capability.

Fabrication of Bi2MoO6/MIL-101 (Fe) Composites for Visible Light Photocatalytic Activity Enhancement

Bi2MoO6/MIL-101 (Fe) composite photocatalyst was prepared by a two-step solvothermal method, the photocatalytic decomposition reaction was carried out using visible light as light source and Congo red (CR) aqueous solution as the simulated dye wastewater. The results showed that the photocatalytic activity of Bi2MoO6/MIL-101 (Fe) composite photocatalyst was better than pure MIL-101(Fe) catalyst for the degradation of CR. Bi2MoO6/MIL-101(Fe) composite photocatalyst could compensate for the slower electron mobility and the easy compounding of photogenerated electron-hole pairs of MIL-101(Fe). The degradation efficiency of Bi2MoO6/MIL-101(Fe) photocatalyst for CR remained high after five cycles, indicating its good stability and reusability.

Effect of increasing Fe catalytic decomposition layer of ammonia on the performance and stability of ammonia electrode

In a direct ammonia proton ceramic fuel cell (DA-PCFC), attaching a catalyst layer on the surface of the ammonia electrode is known to optimize the cell's electrochemical performance and long-term stability. In this study, the Fe catalyst layer is added to the ammonia electrode of the full cell which is prepared with the structure Ni– BaZr0.1Ce0.7Y0.1Yb0.1O3-δ(BZCYYb) (support layer)|Ni-BZCYYb (active layer)|BZCYYb|La0.6Sr0.4Co0.2Fe0.8O3-δ to investigate its impact on the electrochemical performance and stability of the electrode. Under the conditions of 700 oC and 20 ml min−1 ammonia fuel, the peak power densities of cells with and without the Fe layer reach 585.051 and 463.671 mW cm−2, respectively. It is evident that the addition of the Fe catalytic layer significantly improves the electrochemical performance of the cell. Stability tests are carried out for cells with and without the Fe layer at 650 oC, 0.36 A cm−2, and 0.32 A cm−2 constant current discharge. After discharge for 313 and 372 h, both cells show good stability, and the discharge curves of the two cells are consistent after 100 h. The high M-N binding energy of the Fe catalytic layer improved the initial performance of the cell, but this improvement is not sustained over the stability.

Effect of Fe/Mn Ratio on the Catalytic Oxidation of Toluene over Porous γ-Al2O3 Supported Fe and Mn Bimetal Catalysts

Effect of Fe/Mn Ratio on the Catalytic Oxidation of Toluene over Porous γ-Al2O3 Supported Fe and Mn Bimetal Catalysts

Nickel- and/or iron-based ceria-supported catalysts for CO oxidation in combustion exhaust gases

We present a series of Ni, Fe, and mixed NiFe-based catalysts, deposited onto ceria prepared with either soft templated (with CTAB) or hard templated (with SBA-15) syntheses. The prepared materials were thoroughly characterized with SEM, HRTEM, EDX, ICP-MS, PXRD, and N2 adsorption techniques, to fully comprehend their physicochemical properties. All catalysts were then tested for carbon monoxide oxidation reaction at different temperatures, aiming to reach temperature and feed composition conditions typical of combustion exhausts from industrial and power plants (350–400 °C, in the presence of competitive species such as CO2 and H2O in the feed). Advanced reaction tests highlighted outstanding materials (especially NiFe catalyst deposited onto hard-templated ceria), displaying catalytic performances able to compete with those typical of noble metal–based catalysts. Such catalysts were further investigated by means of Raman, NEXAFS, H2–TPR, and CO@FT-IR, unraveling their surface and reduction properties, which make them excellent candidates for replacing more costly noble metal-based catalysts currently employed for CO oxidation reaction.

Reactivity of Ni-modified MIL-100(Fe) catalysts for C3H6-SCR and reaction mechanism

Metal-organic frameworks (MOFs)-based carrier, MIL-100(Fe), was synthesized by hydrothermal method and Ni was supported on the MIL-100(Fe) by wet impregnation method to prepare the catalysts for selective catalytic reduction of NO with C3H6 (C3H6-SCR). The addition of Ni significantly improved the reactivity of C3H6-SCR. At 275 °C, the NO conversion of MIL-100(Fe) was 74.5%, whereas the NO conversion of 5.8%Ni/MIL-100(Fe) with 100% N2 selectivity was 100%. The in-situ DRIFTS prove that the interaction between NO2−/NO3− and CxHyOz substances generated intermediate isocyanates (R-NCO), and the reaction pathway was proposed based on the DRIFTS results to understand the mechanism.

Salt Effect Engineering Single Fe-N2P2-Cl Sites on Interlinked Porous Carbon Nanosheets for Superior Oxygen Reduction Reaction and Zn-Air Batteries.

Developing efficient metal-nitrogen-carbon (M-N-C) single-atom catalysts for oxygen reduction reaction (ORR) is significant for the widespread implementation of Zn-air batteries, while the synergic design of the matrix microstructure and coordination environment of metal centers remains challenges. Herein, a novel salt effect-induced strategy is proposed to engineer N and P coordinated atomically dispersed Fe atoms with extra-axial Cl on interlinked porous carbon nanosheets, achieving a superior single-atom Fe catalyst (denoted as Fe-NP-Cl-C) for ORR and Zn-air batteries. The hierarchical porous nanosheet architecture can provide rapid mass/electron transfer channels and facilitate the exposure of active sites. Experiments and density functional theory (DFT) calculations reveal the distinctive Fe-N2P2-Cl active sites afford significantly reduced energy barriers and promoted reaction kinetics for ORR. Consequently, the Fe-NP-Cl-C catalyst exhibits distinguished ORR performance with a half-wave potential (E1/2) of 0.92V and excellent stability. Remarkably, the assembled Zn-air battery based on Fe-NP-Cl-C delivers an extremely high peak power density of 260mWcm-2 and a large specific capacity of 812mAhg-1, outperforming the commercial Pt/C and most reported congeneric catalysts. This study offers a new perspective on structural optimization and coordination engineering of single-atom catalysts for efficient oxygen electrocatalysis and energy conversion devices.