Browse
Submit Data
Databases
API
Help

Dataset Information

13 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Identification of M-NH₂ -NH₂ Intermediate and Rate Determining Step for Nitrogen Reduction with Bioinspired Sulfur-Bonded FeW Catalyst.

ABSTRACT: The multimetallic sulfur-framework catalytic site of biological nitrogenases allows the efficient conversion of dinitrogen (N₂ ) to ammonia (NH₃ ) under ambient conditions. Inspired by biological nitrogenases, a bimetallic sulfide material (FeWS_x @FeWO₄ ) was synthesized as a highly efficient N₂ reduction (NRR) catalyst by sulfur substitution of the surface of FeWO₄ nanoparticles. Thus prepared FeWS_x @FeWO₄ catalysts exhibit a relatively high NH₃ production rate of 30.2 ug h^-1 mg^-1 _cat and a Faraday efficiency of 16.4 % at -0.45 V versus a reversible hydrogen electrode in a flow cell; these results have been confirmed via purified ¹⁵ N₂ -isotopic labeling experiments. In situ Raman spectra and hydrazine reduction kinetics analysis revealed that the reduction of undissociated hydrazine intermediates (M-NH₂ -NH₂ ) on the surface of the bimetallic sulfide catalyst is the rate-determing step for the NRR process. Therefore, this work can provide guidance for elucidating the structure-activity relationship of NRR catalysts.

SUBMITTER: Zhao Y

PROVIDER: S-EPMC8456964 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

A bioinspired molybdenum-copper molecular catalyst for CO2 electroreduction.

Project description:Non-noble metal molecular catalysts mediating the electrocatalytic reduction of carbon dioxide are still scarce. This work reports the electrochemical reduction of CO2 to formate catalyzed by the bimetallic complex [(bdt)MoVI(O)S2CuICN]2- (bdt = benzenedithiolate), a mimic of the active site of the Mo-Cu carbon monoxide dehydrogenase enzyme (CODH2). Infrared spectroelectrochemical (IR-SEC) studies coupled with density functional theory (DFT) computations revealed that the complex is only a pre-catalyst, the active catalyst being generated upon reduction in the presence of CO2. We found that the two-electron reduction of [(bdt)MoVI(O)S2CuICN]2- triggers the transfer of the oxo moiety to CO2 forming CO3 2- and the complex [(bdt)MoIVS2CuICN]2- and that a further one-electron reduction is needed to generate the active catalyst. Its protonation yields a reactive MoVH hydride intermediate which reacts with CO2 to produce formate. These findings are particularly relevant to the design of catalysts from metal oxo precursors.

| S-EPMC7448372 | biostudies-literature

Sulfur resistance of Ce-Mn/TiO2 catalysts for low-temperature NH3-SCR.

Project description:Ce-Mn/TiO2 catalyst prepared using a simple impregnation method demonstrated a better low-temperature selective catalytic reduction of NO with NH3 (NH3-SCR) activity in comparison with the sol-gel method. The Ce-Mn/TiO2 catalyst loading with 20% Ce had the best low-temperature activity and achieved a NO conversion rate higher than 90% at 140-260°C with a 99.7% NO conversion rate at 180°C. The Ce-Mn/TiO2 catalyst only had a 6% NO conversion rate decrease after 100 ppm of SO2 was added to the stream. When SO2 was removed from the stream, the catalyst was able to recover completely. The crystal structure, morphology, textural properties and valence state of the metals involving the novel catalysts were investigated using X-ray diffraction, N2 adsorption and desorption analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive spectroscopy, respectively. The decrease of NH3-SCR performance in the presence of 100 ppm SO2 was due to the decrease of the surface area, change of the pore structure, the decrease of Ce4+ and Mn4+ concentration and the formation of the sulfur phase chemicals which blocked the active sites and changed the valence status of the elements.

| S-EPMC5882715 | biostudies-literature

Enhanced low-temperature NH3-SCR performance of Ce/TiO2 modified by Ho catalyst.

Project description:Holmium was used as a dopant to boost the low-temperature NH3-selective catalytic reduction (SCR) performance of Ce/TiO2 catalyst. It was ascertained that certain amount of Ho-doping species could exceedingly improve the low-temperature SCR activity under 60 000 h-1 of Ce/TiO2, accompanied with the improvement of tolerance to H2O and SO2 at 200°C. Characterization results manifested that Ho modification could not only result in inhibiting the growth of TiO2 crystals and the enlargement of specific surface area but also lead to the enhanced redox ability and the increased amount of surface-adsorbed substances, all of which could promote the low-temperature NH3-SCR performance of Ce/TiO2.

| S-EPMC6458355 | biostudies-literature

N2 -to-NH3 Conversion by a triphos-Iron Catalyst and Enhanced Turnover under Photolysis.

Project description:Bridging iron hydrides are proposed to form at the active site of MoFe-nitrogenase during catalytic dinitrogen reduction to ammonia and may be key in the binding and activation of N2 via reductive elimination of H2 . This possibility inspires the investigation of well-defined molecular iron hydrides as precursors for catalytic N2 -to-NH3 conversion. Herein, we describe the synthesis and characterization of new P2P'Ph Fe(N2 )(H)x systems that are active for catalytic N2 -to-NH3 conversion. Most interestingly, we show that the yields of ammonia can be significantly increased if the catalysis is performed in the presence of mercury lamp irradiation. Evidence is provided to suggest that photo-elimination of H2 is one means by which the enhanced activity may arise.

| S-EPMC5595421 | biostudies-literature

Experimental identification of aminomethanol (NH2CH2OH)-the key intermediate in the Strecker Synthesis.

Project description:The Strecker Synthesis of (a)chiral α-amino acids from simple organic compounds, such as ammonia (NH3), aldehydes (RCHO), and hydrogen cyanide (HCN) has been recognized as a viable route to amino acids on primordial earth. However, preparation and isolation of the simplest hemiaminal intermediate - the aminomethanol (NH2CH2OH)- formed in the Strecker Synthesis to even the simplest amino acid glycine (H2NCH2COOH) has been elusive. Here, we report the identification of aminomethanol prepared in low-temperature methylamine (CH3NH2) - oxygen (O2) ices upon exposure to energetic electrons. Isomer-selective photoionization time-of-flight mass spectrometry (PI-ReTOF-MS) facilitated the gas phase detection of aminomethanol during the temperature program desorption (TPD) phase of the reaction products. The preparation and observation of the key transient aminomethanol changes our perception of the synthetic pathways to amino acids and the unexpected kinetic stability in extreme environments.

| S-EPMC8770675 | biostudies-literature

Novel TiO2 catalyst carriers with high thermostability for selective catalytic reduction of NO by NH3.

Project description:A series of TiO2 catalyst carriers with ceria additives were prepared by a precipitation method and tested for selective catalytic reduction (SCR) of NO by NH3. These samples were characterized by XRD, N2-BET, NH3-TPD, H2-TPR, TEM, XPS and in situ DRIFTS, respectively. Results showed that the appropriate addition of ceria can enhance the catalytic activity and thermostability of TiO2 catalyst carriers significantly. The maximum catalytic activity of Ti-Ce-Ox-500 is 98.5% at 400 °C with a GHSV of 100 000 h-1 and the high catalytic activity still remains even after the treatment at high temperature for 24 h. The high catalytic performance of Ti-Ce-Ox-500 can be attributed to a series of superior properties, such as larger specific surface area, more Brønsted acid sites, more hydrogen consumption, and the higher proportion of chemisorbed oxygen. Ceria atoms can inhibit the crystalline grain growth and the collapse of small channels caused by high temperatures. Furthermore, in situ DRIFTS in different feed gases show that the SCR reaction over Ti-Ce-Ox-500 follows both E-R and L-H mechanisms.

| S-EPMC6469708 | biostudies-literature

Understanding the Hydrogen-Bonded Clusters of Ammonia (NH3) n (n = 3-6): Insights from the Electronic Structure Theory.

Project description:Although it is well known that hydrogen bonds commonly exist in ammonia clusters and play an important role, there are still many challenges in understanding the electronic structure properties of hydrogen bonds. In this paper, the geometric and electronic structure properties of cyclic ammonia clusters are investigated by using first-principles density functional theory (DFT) and the Møller-Plesset perturbation theory (MP2). The calculation results show that the pentamer and hexamer have deviated from the perfect plane, while the trimer and tetramer present planarization that has been confirmed by infrared (IR) spectra. The electronic structure analysis further shows that the covalent properties play a non-negligible role in hydrogen bonding. The results also indicate that the electronic structure facilitates structure planarization. Our work not only provides insight into the role and nature of hydrogen bonds in ammonia clusters but also provides a theoretical basis for frontier science in fields such as atmospheric haze and biomolecular functions.

| S-EPMC7745437 | biostudies-literature

Hybrid Chlorides with Methylhydrazinium Cation: [CH3NH2NH2]CdCl3 and Jahn-Teller Distorted [CH3NH2NH2]CuCl3.

Project description:The synthesis, structural, phonon, optical, and magnetic properties of two hybrid organic-inorganic chlorides with monoprotonated methylhydrazinium cations (CH3NH2NH2+, MHy+), [CH3NH2NH2]CdCl3 (MHyCdCl3), and [CH3NH2NH2]CuCl3 (MHyCuCl3), are reported. In contrast to previously reported MHyMIICl3 (MII = Mn2+, Ni2+, and Co2+) analogues, neither compound undergoes phase transitions. The MHyCuCl3 has a crystal structure familiar to previous crystals composed of edge-shared 1D chains of the [CuCl5N] octahedra. MHyCuCl3 crystallizes in monoclinic P21/c symmetry with MHy+ cations directly linked to the Cu2+ ions. The MHyCdCl3 analogue crystallizes in lower triclinic symmetry with zig-zag chains of the edge-shared [CdCl6] octahedra. The absence of phase transitions is investigated and discussed. It is connected with slightly stronger hydrogen bonding between cations and the copper-chloride chains in MHyCuCl3 due to the strong Jahn-Teller effect causing the octahedra to elongate, resulting in a better fit of cations in the accessible space between chains. The absence of structural transformation in MHyCdCl3 is due to intermolecular hydrogen bonding between two neighboring MHy+ cations, which has never been reported for MHy+-based hybrid halides. Optical investigations revealed that the bandgaps in Cu2+ and Cd2+ analogues are 2.62 and 5.57 eV, respectively. Magnetic tests indicated that MHyCuCl3 has smeared antiferromagnetic ordering at 4.8 K.

| S-EPMC9865361 | biostudies-literature

Unraveling the rate-determining step of C2+ products during electrochemical CO reduction.

Project description:The electrochemical reduction of CO has drawn a large amount of attention due to its potential to produce sustainable fuels and chemicals by using renewable energy. However, the reaction's mechanism is not yet well understood. A major debate is whether the rate-determining step for the generation of multi-carbon products is C-C coupling or CO hydrogenation. This paper conducts an experimental analysis of the rate-determining step, exploring pH dependency, kinetic isotope effects, and the impact of CO partial pressure on multi-carbon product activity. Results reveal constant multi-carbon product activity with pH or electrolyte deuteration changes, and CO partial pressure data aligns with the theoretical formula derived from *CO-*CO coupling as the rate-determining step. These findings establish the dimerization of two *CO as the rate-determining step for multi-carbon product formation. Extending the study to commercial copper nanoparticles and oxide-derived copper catalysts shows their rate-determining step also involves *CO-*CO coupling. This investigation provides vital kinetic data and a theoretical foundation for enhancing multi-carbon product production.

| S-EPMC10828390 | biostudies-literature

Flexibility Enhances Reactivity: Redox Isomerism and Jahn-Teller Effects in a Bioinspired Mn4O4 Cubane Water Oxidation Catalyst.

Project description:Understanding how water oxidation to molecular oxygen proceeds in molecular metal-oxo catalysts is a challenging endeavor due to their structural complexity. In this report, we unravel the water oxidation mechanism of the highly active water oxidation catalyst [Mn4V4O17(OAc)3]3-, a polyoxometalate catalyst with a [Mn4O4]6+ cubane core reminiscent of the natural oxygen-evolving complex. Starting from the activated species [Mn4 4+V4O17(OAc)2(H2O)(OH)]1-, we scrutinized multiple pathways to find that water oxidation proceeds via a sequential proton-coupled electron transfer (PCET), O-O bond formation, another PCET, an intramolecular electron transfer, and another PCET resulting in O2 evolution, with a predicted thermodynamic overpotential of 0.71 V. An in-depth investigation of the O-O bond formation process revealed an essential interplay between redox isomerism and Jahn-Teller effects, responsible for enhancing reactivity in the catalytic cycle. This is achieved by redistributing electrons between metal centers and weakening relevant bonds through Jahn-Teller distortions, introducing flexibility to the otherwise rigid cubane core of the catalyst. These mechanistic insights are expected to advance the design of efficient bioinspired Mn cubane water-splitting catalysts.

| S-EPMC8576808 | biostudies-literature