CO Precursor Research Articles

Ultrasound-driven self-decomposition porphyrins as metal-free CO precursors for gas and sonodynamic synergistic therapy

Ultrasound-driven self-decomposition porphyrins as metal-free CO precursors for gas and sonodynamic synergistic therapy

Co(II)-Cu(II) mixed-oxide catalysts for single-step synthesis of 2,4,5-triaryl-1H-imidazole derivatives under microwave irradiation.

In this study, a catalyst composite of Co-Cu was prepared from chloride-containing precursor of Co(II) and Cu(II) metals using the milky latex of the Euphorbia neriifolia plant following green principles of synthesis. The catalyst composite was characterized using XRD, EDAX, SEM, HR-TEM, FTIR, XPS and TOF-MS. The crystallinity of the mixed-oxide composite with a distorted octahedral nature was confirmed from analysis. Chemical charge analysis of the Co-Cu mixed phase based on XPS revealed Co2+ and Cu2+ oxidation states. This material was used for synthesizing 2,4,5-triaryl-1H-imidazole (TIMDZOL) derivatives. Analysis of reaction conditions revealed that EtOH : PEG at 8 : 2 ratio under microwave conditions showed better yields with less time and better reusability of the Co-Cu catalyst.

Three-dimensional self-supporting micro-nanostructured MoS2/CoS2/CC heterojunction derived from ZIF-67 for high efficiency electrocatalytic hydrogen evolution in both acid and alkali electrolytes

In this paper, a novel three-dimensional (3D) MoS2/CoS2 micro-nano heterostructured electrocatalyst has been successfully derived from ZIF-67 on carbon cloth (CC) by a simple method of low temperature vulcanization. The metal-organic framework (MOFs) of ZIF-67 on CC was obtained at room temperature and used as both the precursor of Co and structure template to construct the 3D self-supporting spindle CoS2 nanodiscs on CC. Large amounts of 2D MoS2 nanosheets were subsequently grown on the surface of spindle-shaped CoS2 nanodiscs to form 3D self-supporting MoS2/CoS2/CC heterostructural electrocatalyst. This 3D self-supporting heterostructural electrocatalyst showed good hydrogen evolution reaction (HER) performance in both acid and alkali electrolytes. At 10 mA/cm2, the HER overpotentials of the MoS2/CoS2/CC heterostructural electrocatalyst in the alkali and acid electrolyte were 147 mV and 119 mV, and their corresponding Tafel slopes were 90.5 mV dec−1 and 111.4 mV dec−1, respectively, indicating that this MoS2/CoS2/CC heterostructural electrocatalyst had a good application prospect in the electrolysis of water to produce hydrogen. Moreover, this work provides a new idea for low-cost, scale fabrication of 3D self-supporting heterostructured transition metal sulfide catalysts.

Al‐Cu‐Fe alloys in the solar system: Going inside a Khatyrka‐like micrometeorite (KT01) from the Nubian Desert, Sudan

AbstractA recently described micrometeorite from the Nubian desert (Sudan) contains an exotic Al‐Cu‐Fe assemblage closely resembling that observed in the Khatyrka chondrite (Suttle et al., 2019; Science Reports 9:12426). We here extend previous investigations of the geochemical, mineralogical, and petrographic characteristics of the Sudan spherule by measuring oxygen isotope ratios in the silicate components and by nano‐scale transmission electron microscopy study of a focused ion beam foil that samples the contact between Al‐Cu alloys and silicates. O‐isotope work indicates an affinity to either OC or CR chondrites, while ruling out a CO or CM precursor. When combined with petrographic evidence we conclude that a CR chondrite parentage is the most likely origin for this micrometeorite. SEM and TEM studies reveal that the Al‐Cu alloys mainly consist of Al metal, stolperite (CuAl), and khatyrkite (CuAl2) together with inclusions in stolperite of a new nanometric, still unknown Al‐Cu phase with a likely nominal Cu3Al2 stoichiometry. At the interface between the alloy assemblage and the surrounding silicate, there is a thin layer (200 nm) of almost pure MgAl2O4 spinel along with well‐defined and almost perfectly spherical metallic droplets, predominantly iron in composition. The study yields additional evidence that Al‐Cu alloys, the likely precursors to quasicrystals in Khatyrka, occur naturally. Moreover, it implies the existence of multiple pathways leading to the association in reduced form of these two elements, one highly lithophile and the other strongly chalcophile.

Size-controlled Co/CoO heterogeneous nanoparticles confined in N-doped mesoporous carbon for efficient oxygen reduction in zinc-air batteries

The size of metal compound particles and interface electronic structure of heterojunctions in a matrix greatly affect oxygen reduction performance in zinc-air batteries. However, it is still a big challenge to precisely control or regulate the size of these metal compound particles and the heterojunction structure. Herein, cobalt complexes with different-sized ligands are chosen as cobalt resources and adsorbed onto a mesoporous carbon, after which they are coated with polydopamine and calcined. Under the confinement effect of mesopores and the isolation effect of ligands and dopamine, the as-obtained Co/CoO heterogeneous nanoparticles are restricted to nano-size and uniformly dispersed in N-doped carbon (NC). The sizes of Co/CoO are estimated to be 39.7, 24.9 and 15.6 nm with increased CoO contents, corresponding to the adopted cobalt precursors of Co(OAc)2, Co(acac)2 and Co(acac)3, respectively. The smallest Co/CoO/NC-S shows excellent catalytic activity for oxygen reduction reaction, with a half-wave potential of 0.82 V vs. RHE and a limiting current density of 4.59 mA cm−2. When applied to the cathode of zinc-air battery, a high peak power density of 131.9 mW cm−2 is achieved, which surpasses that of the battery powered by Pt/C. The excellent performance can be attributed to the formation of heterogeneous structures between Co and CoO, the smaller Co/CoO nanoparticles, and N-doped mesoporous carbon with effective charge/mass transport. This work provides an effective way to regulate the size and phase contents of heterogeneous particles in mesoporous carbon, which is highly valuable in electrocatalytic systems.

Synthesis, Reactivity and Coordination Chemistry of Group 9 PBP Boryl Pincer Complexes: [(PBP)M(PMe3)n] (M = Co, Rh, Ir; n = 1, 2).

The unsymmetrical diborane(4) derivative [(d(CH2P(iPr)2)abB)-Bpin] (1) proved to be a versatile PBP boryl pincer ligand precursor for Co(I) (2a, 4a), Rh(I) (2-3b) and Ir(I/III) (2-3c, 5-6c) complexes, in particular of the types [(d(CH2P(iPr)2)abB)M(PMe3)2] (2a-c) and [(d(CH2P(iPr)2)abB)M-PMe3] (2b-c). Whilst similar complexes have been obtained before, for the first time, the coordination chemistry of a homologous series of PBP pincer complexes, in particular the interconversion of the five- and four-coordinate complexes 2a-c/3a-c, was studied in detail. For Co, instead of the mono phosphine complex 2a, the dinitrogen complex [(d(CH2P(iPr)2)abB)Co(N2)(PMe3)] (4a) is formed spontaneously upon PMe3 abstraction from 2a in the presence of N2. All complexes were comprehensively characterised spectroscopically in solution via multinuclear (VT-)NMR spectroscopy and structurally in the solid state through single-crystal X-ray diffraction. The unique properties of the PBP ligand with respect to its coordination chemical properties are addressed.

Illustrating new understanding of adsorbed water on silica for inducing tetrahedral cobalt(II) for propane dehydrogenation

Highly dispersed metal sites on the surface of silica, achieved from immobilization of metal precursor within hydroxyl groups, has gained increasing attention in the field of heterogeneous catalyst. However, the special role of adsorbed water derived by hydroxyl groups on the silica is generally ignored. Herein, a new understanding of adsorbed water on the formation of highly dispersed tetrahedral Co(II) (Td-cobalt(II)) sites is illustrated. It is indicated that sufficient adsorbed water induces the transformation of precursor of Co(NO3)2 into intermediate of [Co(H2O)6]2+. Subsequently, [Co(H2O)6]2+ makes the highly dispersed Td-cobalt(II) sites to be available during direct H2-reduction process. A systematic characterization and DFT calculation prove the existence of the adsorbed water and the importance of the intermediate of [Co(H2O)6]2+, respectively. The as-synthesized catalyst is attempted to the propane dehydrogenation, which shows better reactivity when compared with other reported Co based catalysts.

Hexaamminecobalt(III)] Dichloride Permanganate—Structural Features and Heat-Induced Transformations into (CoII,MnII)(CoIII,MnIII)2O4 Spinels

We synthesized and characterized (IR, Raman, UV, SXRD) hexaamminecobalt(III) dichloride permanganate, [Co(NH3)6]Cl2(MnO4) (compound 1) as the precursor of Co–Mn–spinel composites with atomic ratios of Co:Mn = 1:1 and 1:3. The 3D−hydrogen bond network includes N–HO–Mn and N–HCl interactions responsible for solid-phase redox reactions between the permanganate anions and ammonia ligands. The temperature-limited thermal decomposition of compound 1 under the temperature of boiling toluene (110 ∘C) resulted in the formation of (NH4)4Co2Mn6O12. which contains a todorokite-like manganese oxide network (MnII4MnIII2O1210−). The heat treatment products of compounds 1 and [Co(NH3)5Cl](MnO4)2 (2) synthesized previously at 500 ∘C were a cubic and a tetragonal spinel with Co1.5Mn1.5O4 and CoMn2O4 composition, respectively. The heating of the decomposition product of compounds 1 and 2 that formed under refluxing toluene (a mixture with an atomic ratio of Co:Mn = 1:1 and 1:2) and after aqueous leaching ((NH4)4Co2Mn6O12, 1:3 Co:Mn atomic ratio in both cases) at 500 ∘C resulted in tetragonal Co0.75Mn2.25O4 spinels. The Co1.5Mn1.5O4 prepared from compound 1 at 500 ∘C during the solid-phase decomposition catalyzes the degradation of Congo red with UV light. The decomposition rate of the dye was found to be nine times faster than in the presence of the tetragonal CoMn2O4 spinel prepared in the solid-phase decomposition of compound 2. The todorokite-like intermediate prepared from compound 1 under N2 at 115 ∘C resulted in a 54 times faster degradation of Congo red, which is a great deal faster than the same todorokite-like phase that formed from compound 2 under N2.

The reaction mechanism and sulfur evolution during vulcanized nature rubber pyrolysis in the atmosphere of H2O: A ReaxFF molecular dynamics study

In this work, the evolution of pyrolytic products of nature rubber (NR) and vulcanized NR were studied by performing a series of ReaxFF molecular dynamics simulations. The simulations under different temperatures (2400, 2600, 2800, 3000 K) were performed to investigate the influence of temperature on the distribution and characterization of product. The effect of water on product distribution and sulfur evolution during vulcanized NR pyrolysis were investigated by adding different amount of water molecules (50 and 200) into reaction systems. The mechanism of water molecules promoting the decomposition of vulcanized NR was discussed and proposed. The results show that vulcanized cross-linked structure promotes the decomposition of carbon chains resulting more gas product at low temperature. Water can promote the further decomposition of heavy and light tars into gas product and inhibit the secondary formation of heavy tar. Moreover, water also facilitate the transfer of sulfur atoms to H2S and reduce the content of thiophene compounds at high temperature. Results indicate that water condition can provide a stronger cracking environment by generating OH radicals and reacting with intermediate products of vulcanized NR pyrolysis forming R-C-OH radicals, which are the main precursors of CO and other oxygen-containing products.

Copper Carbonate Hydroxide as Precursor of Interfacial CO in CO2 Electroreduction.

Copper electrodes are especially effective in catalysis of C2 and further multi‐carbon products in the CO2 reduction reaction (CO2RR) and therefore of major technological interest. The reasons for the unparalleled Cu performance in CO2RR are insufficiently understood. Here, the electrode–electrolyte interface was highlighted as a dynamic physical‐chemical system and determinant of catalytic events. Exploiting the intrinsic surface‐enhanced Raman effect of previously characterized Cu foam electrodes, operando Raman experiments were used to interrogate structures and molecular interactions at the electrode–electrolyte interface at subcatalytic and catalytic potentials. Formation of a copper carbonate hydroxide (CuCarHyd) was detected, which resembles the mineral malachite. Its carbonate ions could be directly converted to CO at low overpotential. These and further experiments suggested a basic mode of CO2/carbonate reduction at Cu electrodes interfaces that contrasted previous mechanistic models: the starting point in carbon reduction was not CO2 but carbonate ions bound to the metallic Cu electrode in form of CuCarHyd structures. It was hypothesized that Cu oxides residues could enhance CO2RR indirectly by supporting formation of CuCarHyd motifs. The presence of CuCarHyd patches at catalytic potentials might result from alkalization in conjunction with local electrical potential gradients, enabling the formation of metastable CuCarHyd motifs over a large range of potentials.

Preparation of high entropy nitride ceramic nanofibers from liquid precursor for CO2 photocatalytic reduction

AbstractSubjected to the manufacturing methods (sputtering or mechanochemical synthesis), the reported high entropy nitrides (HENs) were limited to the forms of coating and powder. Here, we report a novel strategy in preparing HEN ceramic nanofibers (HENCNFs) from liquid precursor via electrospinning followed by high‐temperature NH3 atmosphere nitridation. The as‐prepared HENCNFs include five uniform dispersed metal elements, Ti, Hf, Nb, Ta, and Mo, and have a single face‐centered cubic structure. Interestingly, the obtained HENCNFs show photocatalyst activity in CO2 reduction. The product selectivity of photocatalytic CO2 reduction reaction is 96.4%, and no performance degradation was detected during five cycles photocatalysis test.

How palladium inhibits CO poisoning during electrocatalytic formic acid oxidation and carbon dioxide reduction

Development of reversible and stable catalysts for the electrochemical reduction of CO2 is of great interest. Here, we elucidate the atomistic details of how a palladium electrocatalyst inhibits CO poisoning during both formic acid oxidation to carbon dioxide and carbon dioxide reduction to formic acid. We compare results obtained with a platinum single-crystal electrode modified with and without a single monolayer of palladium. We combine (high-scan-rate) cyclic voltammetry with density functional theory to explain the absence of CO poisoning on the palladium-modified electrode. We show how the high formate coverage on the palladium-modified electrode protects the surface from poisoning during formic acid oxidation, and how the adsorption of CO precursor dictates the delayed poisoning during CO2 reduction. The nature of the hydrogen adsorbed on the palladium-modified electrode is considerably different from platinum, supporting a model to explain the reversibility of this reaction. Our results help in designing catalysts for which CO poisoning needs to be avoided.

Atomically dispersed Co–N–C electrocatalysts synthesized by a low-speed ball milling method for proton exchange membrane fuel cells

A green method of low-speed ball milling was applied to synthesize the precursor of Co–N–C catalysts with high performance.

TFBen (Benzene-1,3,5-triyl triformate): A Powerful and Versatile CO Surrogate.

Carbonylative reactions by the using of CO surrogates constitute a facile avenue for the assembly of valuable carbonyl-containing compounds due to the colorless, toxic, flammable, and not easy-handing character of carbon monoxide gas. Recent advances in the carbonylative transformations with TFBen (benzene-1,3,5-triyl triformate) as a safe and convenient CO precursor are systematically summarized and discussed, which can be divided into three parts based on the patterns of the obtained products. This Review focuses on the discussion of the application of TFBen in carbonylative synthesis of various carbonyl-containing compounds.

Covariation of Airborne Biogenic Tracers (CO2, COS, and CO) Supports Stronger Than Expected Growing Season Photosynthetic Uptake in the Southeastern US

AbstractThe Atmospheric Carbon Transport (ACT)‐America Earth Venture mission conducted five airborne campaigns across four seasons from 2016 to 2019, to study the transport and fluxes of Greenhouse gases across the eastern United States. Unprecedented spatial sampling of atmospheric tracers (CO2, carbon monoxide [CO], carbonyl sulfide [COS]) related to biospheric processes offers opportunities to improve our qualitative and quantitative understanding of seasonal and spatial patterns of biospheric carbon uptake. Here, we examine co‐variation of boundary layer enhancements of CO2, CO, and COS across three diverse regions: the crop‐dominated Midwest, evergreen‐dominated South, and deciduous broadleaf‐dominated Northeast. To understand the biogeochemical processes controlling these tracers, we compare the observed co‐variation to simulated co‐variation resulting from model‐ and satellite‐ constrained surface carbon fluxes. We found indication of a common terrestrial biogenic sink of CO2 and COS and secondary production of CO from biogenic sources in summer throughout the eastern US, driven by stomatal conductance. Upper Midwest crops drive CO2 and COS depletion from early to late summer. Northeastern temperate forests drive CO2 and COS depletion in late summer. The unprecedented ACT‐America flask samples uncovered evidence that southern humid temperate forests photosynthesize and absorb CO2 and COS, and emit CO precursors, deep into the growing season. Satellite‐ constrained carbon fluxes capture much of the observed seasonal and spatial variability, but underestimate the magnitude of net CO2 and COS depletion in the South, indicating a stronger than expected net sink of CO2 in late summer. Additional sampling of the South will more accurately constrain underlying biological processes and climate sensitivities governing southern carbon dynamics.

Hydrodeoxygenation of lignin-derived phenolics over facile prepared bimetallic RuCoNx/NC

Cyclohexanols, promising oxygenated fuel additives and value-added chemicals, can be obtained by hydrodeoxygenation (HDO) of lignin-derived phenolics. Here, an N-doped bimetallic RuCoNx/NC catalyst was facilely prepared for HDO by direct pyrolysis of chitin impregnated with precursors of Ru and Co. Characterization of RuCoNx/NC with N2 sorption, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and NH3 temperature-programmed desorption (NH3-TPD) reveal that the metallic particles of electron-deficient Ru species and electron-enriched Co species were uniformly anchored on the micro-mesoporous N-doped carbon matrix with high dispersion and nano-scale size. The abundant accessible active sites and continuous spillover of H from Ru to Co make RuCoNx/NC an excellent HDO catalyst. 4-Propylguaiacol, a typical phenolic compound from lignin degradation, was hydrodeoxygenated into 92% 4-propylcyclohexanol over RuCoNx/NC at 210 ℃. With temperature increasing, propylcyclohexane became the major product, possessing 95% selectivity at 280 °C after 6 h. Reusability tests show that RuCoNx/NC can be recycled four times without the loss of conversion and initial selectivity. HDO of other phenolic compounds confirms the general applicability of RuCoNx/NC.

Palladium-catalyzed carbonylative synthesis of 3-arylquinolin-2(1H)-ones from benzyl chlorides and o-nitrobenzaldehydes

• A general and straightforward palladium-catalyzed aminocarbonylation procedure of benzyl chlorides have been developed. • o- nitrobenzaldehydes have been used as stable nitrogen sources for the synthesis of 3-arylquinolin-2(1 H )-ones. • Mo(CO) 6 has been used both as CO precursor and reductant. A palladium-catalyzed carbonylative cyclization of benzyl chlorides with o- nitrobenzaldehydes has been developed for the synthesis of 3-arylquinolin-2(1 H )-ones. Mo(CO) 6 played a dual role as both a CO surrogate and a reductant in this carbonylative transformation.

Investigation on solid state pyrolytic decomposition of bimetallic fumarate and tartrate precursors of Co (II), Ni (II) and Zn (II) with manganese

The complexes of Co (II), Ni (II), and Zn (II) with manganese were synthesized by co-precipitation techniques such as fumarates and tartrates. The formation of these dicarboxylate complexes characterized by elemental analysis, infrared spectroscopy, and X-ray powder diffraction studies. The thermal decomposition behaviors of these complexes were investigated using thermal analysis (TGA, DTG, and DTA) and d. c. electrical conductivity measurements under normal atmosphere. Based on conductivity measurements and isothermal studies, a probable mechanism for the decomposition was proposed. After dehydration, the anhydrous complexes decompose to yield respective carbonate intermediate in the temperature range 200 – 350 °C. Decomposition of this carbonate species to the formation of the respective spinel in the temperature ranges 350 – 500 °C. The infrared spectra and X-ray powder diffraction studies were made for the identification of intermediate products. The X-ray diffraction studies of the end product indicate that spinel such as CoMn2O4, NiMn2O4, and ZnMn2O4 formed as a final product. The electrical conductivity measurements were found to give additional information on the solid-state reaction as compared to that obtained from conventional thermal techniques (such as TGA, DTG, and DTA).

A simple method for the synthesis of anatase-rutile mixed phase TiO2 using a convenient precursor and higher visible-light photocatalytic activity of Co–doped TiO2

This work reports a novel and simple method for the synthesis of mixed phase TiO2 (Anatase 70% and Rutile 30%). Refluxing aqueous solution of potassium titanyl oxide oxalate lead to direct crystallization of titanium oxalate complex [Ti2O3(H2O)2(C2O4).3H2O] and this complex on calcination at 450 ˚C for one hour yielded TiO2 powder. The powder samples were characterized by XRD, Raman spectroscopy, FESEM-EDX, TEM, XPS, FT-IR, UV–Visible spectroscopy and BET techniques. The XRD, TEM and Raman spectra of TiO2 indicates the coexistence of anatase and rutile phases. The XRD result shows that the primary particle size of anatase crystals is 8.3 nm and that of rutile crystals is 35 nm. From the UV–Visible DRS spectrum, the bandgap of TiO2 was found to be 3.0 eV. Co–doped TiO2 (Co:Ti ratio 1:99) was prepared by adding cobalt nitrate to the precursor solution. On Co–ion doping, anatase:rutile composition was changed to 84:16. The visible light photocatalytic activity of Co–doped TiO2 was found to be better than that of undoped and Degussa TiO2 due to higher visible light absorption caused by Co2+ energy levels due lowered bandgap.

Effect of the Chemical Structure of Hydrocarbons on the Emissions of CO, CO2 and Soot Precursors Issued from Cyclohexane and Benzene Premixed Flames

Effect of the Chemical Structure of Hydrocarbons on the Emissions of CO, CO2 and Soot Precursors Issued from Cyclohexane and Benzene Premixed Flames