Formation Of Hydrocarbons Research Articles

Threshold Photoelectron Spectrum of 3,4‐Dimethylenecyclobutene

We report a study on the photoionization of the C6H6 isomer 3,4‐dimethylenecyclobutene, DMCB. The molecule is an intermediate in the formation of benzene from the propargyl radical self‐reaction, a suggested first step in the formation of polycyclic aromatic hydrocarbons and soot. From a threshold photoelectron spectrum we determine an adiabatic ionization energy of 8.75 eV. The geometry change upon ionization is associated with considerable vibrational activity, which is assigned to a symmetric in‐plane bending mode of the =CH2 groups. A breakdown diagram shows that the dissociative photoionization resembles the one observed for benzene. Computations reveal that DMCB cation isomerizes to the benzene cation and dissociates from there.

Extreme value theory analysis of high emitter trends across four US cities from 1995 to 2021.

Extreme value theory provides a direct means to characterize the distribution of high emitters within a vehicle fleet and calculate statistical confidence intervals for comparisons. Defining a "high emitter" as the maximum emitter in a random sample of N vehicles implies in the limit of large N that high emitters follow an extreme value distribution, comprised of three distinct domains. The analysis of over twenty years of roadside remote sensing emissions measurements in Chicago, Denver, Los Angeles and Tulsa reveals clear differences between gasoline vehicle high emitter distributions across pollutants (hydrocarbons (HC), carbon monoxide (CO) and nitric oxide (NO)), but very similar behavior across the four cities. As Federal emissions regulations became more stringent, HC and CO high emitters evolved from distributions bounded by the stoichiometric limits of HC and CO formation in an engine to progressively longer tailed distributions. In contrast, NO high emitter distributions have changed little over this time period. These distinct behaviors likely reflect differences in the failure mechanisms leading to high HC, CO, versus NO emissions. Whereas average HC, CO and NO fleet emissions fell dramatically over these two plus decades by factors of about 4, 6 and 7, respectively, mean high emitter emissions declined by less than half of these. The paper examines in detail similarities and differences in high emitter distributions versus pollutant, city and vehicle type, how these changed over a period of roughly twenty years and the policy implications that can be drawn.

Production of linear alkanes via the solid-state hydrogenation of interstellar polyynes

Highly unsaturated carbon chains, including polyynes, have been detected in many astronomical regions and planetary systems. With the success of the QUIJOTE survey of the Taurus Molecular Cloud-1 (TMC-1), the community has seen a "boom" in the number of detected carbon chains. On the other hand, the Rosetta mission revealed the release of fully saturated hydrocarbons, C_3H_8, C_4H_10, C_5H_12, and (under specific conditions) C_6H_14 with C_7H_16, from the comet 67P/Churyumov-Gerasimenko. The detection of the latter two is attributed to dust-rich events. Similarly, the analysis of samples returned from asteroid Ryugu by Hayabusa2 mission indicates the presence of long saturated aliphatic chains in Ryugu's organic matter. The surface chemistry of unsaturated carbon chains under conditions resembling those of molecular clouds can provide a possible link among these independent observations. However, laboratory-based investigations to validate such a chemistry is still lacking. In the present study, we aim to experimentally verify the formation of fully saturated hydrocarbons by the surface hydrogenation of C_2nH_2 (n>1) polyynes under ultra-high vacuum conditions at 10 K. We undertook a two-step experimental technique. First, a thin layer of C_2H_2 ice was irradiated by UV-photons (≥ 121 nm) to achieve a partial conversion of C_2H_2 into larger polyynes: C_4H_2 and C_6H_2. Afterwards, the obtained photoprocessed ice was exposed to H atoms to verify the formation of various saturated hydrocarbons. In addition to C_2H_6, which was investigated previously, the formation of larger alkanes, including C_4H_10 and (tentatively) C_6H_14, is confirmed by our study. A qualitative analysis of the obtained kinetic data indicates that hydrogenation of HCCH and HCCCCH triple bonds proceeds at comparable rates, given a surface temperature of 10 K. This can occur on the timescales typical for the dark cloud stage. A general pathway resulting in formation of other various aliphatic organic compounds by surface hydrogenation of N- and O-bearing polyynes is also proposed. We also discuss the astrobiological implications and the possibility of identifying alkanes with JWST.

The Role of the Emeishan Large Igneous Province in Hydrocarbon Formation in the Anyue Gas Field, Sichuan Basin, China

The Role of the Emeishan Large Igneous Province in Hydrocarbon Formation in the Anyue Gas Field, Sichuan Basin, China

Beta‐carotene and astaxanthin inhibit the formation of polycyclic aromatic hydrocarbons and oxygenated polycyclic aromatic hydrocarbons in butter during heat treatment

Polycyclic aromatic hydrocarbons (PAHs) generated from heating butter pose a potential threat to consumer health. This study involved heating butter under different conditions and analysing the changes in the content of 54 PAHs. Furthermore, we investigated the inhibitory effects of β‐carotene, pure astaxanthin and astaxanthin microcapsule powder on PAH formation. Results showed that heating temperature and duration affect the formation and transformation of PAHs, with higher temperatures facilitating the synthesis of oxygenated PAHs, whereas longer heating times promote the accumulation of light PAHs. Despite an observed increase in the concentration of light PAHs following heat treatment with added antioxidants, the antioxidants significantly reduced the toxic equivalency quotients (TEQs) in butter. This study revealed the PAH production pattern during butter heating and the effectiveness of antioxidants in inhibiting their accumulation.

Soot particle morphology and polycyclic aromatic hydrocarbons formation molecular dynamics during diffusion combustion of three pentanol biofuels

Soot particles constitute a major pollutant in engine diffusion combustion, posing a serious threat to human health and the atmospheric environment. The employment of carbon-neutral biofuel, pentanol, in engines contributes to reducing soot emissions; however, its effectiveness is contingent upon the position of the OH functional group. This work investigated the soot morphology and microstructural parameters evolution of three pentanol isomers, and explored the influence mechanism of OH functional group positional isomerism on the entire process of PAHs formation at the atomic level. The results showed that the peak of primary particle size and soot volume fraction in pentanol flames showed a trend of 2-pentanol>3-pentanol>1-pentanol, and the initial formation time of soot in 1-pentanol flame is the latest, and the particle aggregate size is the smallest. The entire process of pentanol isomers soot formation can be divided into four stages: fuel pyrolysis forming initial ring, PAHs growing into initial soot, soot chain growth and structural evolution, soot morphology transformation and maturation. Among the three isomers, 2-pentanol has the fastest initial ring formation rate, the highest peak C-number in the largest molecule, and ultimately forms a more mature fullerene-like structure. 1-pentanol has the slowest initial ring formation rate, the lowest peak C-number in the largest molecule, ultimately forms a lower maturity layered structure. In terms of reaction pathways, H-atom abstraction and dehydroxylation reactions jointly dominate the initial decomposition pathway in 1-pentanol combustion, while in 2-pentanol, dehydroxylation becomes the main initial decomposition pathway due to the high stability of H atoms on β‑carbon. The dehydroxylation reaction tends to generate olefins, promoting the generation of C1-C4 hydrocarbon. The oxygen atom bonded on the α‑carbon site exhibits a stronger carbon fixation ability, and C1-C4 hydrocarbons are more inclined to participate in oxidation to form CO rather than promote the soot production.

Lithology Prediction Using K-Nearest Neighbors (KNN) Algorithm Study Case In Upper Cibulakan Formation

Abstract Knowledge in the characterization and evaluation of hydrocarbon formations by identifying the type of lithology is an important step in oil and gas exploration. However, this method is not efficient enough because it requires a lot of time and effort. This study focuses on lithology predictions using log data input by applying one of the machine learning algorithms, namely K-Nearest Neighbors (KNN). This KNN algorithm can classify data based on K values to predict lithology. The Hyperparameter K value is determined based on the number of nearest neighbors calculated using the Euclidean distance principle. The K value in KNN needs to be optimized in order to find out the best K value to get high accuracy. The accuracy value of the model is obtained by comparing the results of the actual qualitative interpretation of lithology with the prediction results of lithology with KNN resulting precision, recall and F1 as representative of model accuracy. In the data train wells KP-24, KP-54 and KP-57 as well as test data, namely the KP-34 well, the value of k = 5 has the highest accuracy value of 89.9%. With the dominance of lithology in the predicted results, namely limestone, according to the information on the well data area, namely the Cibulakan Formation above and into the well, it reaches the Baturaja Formation. These results indicate that the lithology predicted by the KNN algorithm from the train data is already representative of the actual lithology data. Comparison of the results of qualitative interpretation with the results of machine learning predictions on the KP-34 well can predict thin or small layers and data labels in a relatively short time.

A detailed analysis of the key steps of the cyclopentene autoignition mechanism from calculated RRKM rate constants associated with ignition delay time simulations

Cyclopentene, a prototype for studying the combustion chemistry of cyclic olefins, appears in the oxidation of cyclic hydrocarbons and can provide key information in the understanding of the formation of polycyclic aromatic hydrocarbons. The ▪ addition to the double-bond is one of the main steps in low-temperature oxidation mechanisms of unsaturated organic compounds. In the case of cyclopentene, addition of ▪ yields a hydroxycyclopentyl radical, that can further react with O2. In this work, we studied the potential energy surface and reaction rates for the subsequent reactions of O2 with the hydroxycyclopentyl radical. The temperature and pressure dependence of the rate constants were determined using master equation simulations, with microcanonical rate coefficients calculated by RRKM theory. The potential energy surface was extracted from high-level electronic structure theory, based on geometries and frequencies obtained using density functional theory. Our results indicate that a Waddington-type mechanism, which produces glutaraldehyde and regenerates ▪ , is the dominant reaction pathway. However, at low-temperatures, a secondary pathway leading to the formation of epoxycyclopentanol and ▪ becomes equally significant. The thermochemistry of all ▪ radicals involved were also evaluated. The kinetic and thermodynamic data were incorporated into a comprehensive mechanism of cyclopentene autoignition, in order to simulate the associated ignition delays. The updated reaction mechanism resulted in shorter ignition delays compared to the non-updated mechanism. Sensitivity analysis was performed to identify the primary contributors.Novelty and Significance StatementCyclopentene is an important intermediate in the oxidation of cyclic olefins and serves as a precursor in the formation of polycyclic aromatic hydrocarbons. Kinetic modeling studies require detailed information on elementary reactions, much of which is typically unavailable from experiments. The novelty and significance of this study lie in the theoretical calculations of rate constants for key reactions in the oxidation of cyclopentene and their evaluation within the comprehensive mechanism proposed by Lokachari et al. The results demonstrate that the studied reactions significantly influence the ignition delays of cyclopentene at low temperatures. Furthermore, the data presented here can be applied in future studies focusing on the oxidation of cyclic olefins.

The role of manganese in CoMnOx catalysts for selective long-chain hydrocarbon production via Fischer-Tropsch synthesis

Cobalt is an efficient catalyst for Fischer−Tropsch synthesis (FTS) of hydrocarbons from syngas (CO + H2) with enhanced selectivity for long-chain hydrocarbons when promoted by Manganese. However, the molecular scale origin of the enhancement remains unclear. Here we present an experimental and theoretical study using model catalysts consisting of crystalline CoMnOx nanoparticles and thin films, where Co and Mn are mixed at the sub-nm scale. Employing TEM and in-situ X-ray spectroscopies (XRD, APXPS, and XAS), we determine the catalyst’s atomic structure, chemical state, reactive species, and their evolution under FTS conditions. We show the concentration of CHx, the key intermediates, increases rapidly on CoMnOx, while no increase occurs without Mn. DFT simulations reveal that basic O sites in CoMnOx bind hydrogen atoms resulting from H2 dissociation on Co0 sites, making them less available to react with CHx intermediates, thus hindering chain termination reactions, which promotes the formation of long-chain hydrocarbons.

Effect of Zataria multiflora essential oil, saffron infusion, and fat content on the formation of polycyclic aromatic hydrocarbons, organoleptic score, and toxic potency of Kebab Koobideh

Kebab Koobideh ranks among the most popular in Iran, Turkey, and other countries. This product is prepared by mixing minced meat, onion, and various spices. The objective of our study was to examine the influence of Zataria multiflora essential oil (ZMEO), fat, and saffron infusion as independent variables on the formation of four polycyclic aromatic hydrocarbons (PAH4) and sensory attributes of Kebab Koobideh. The findings indicated that all independent variables exerted a significant impact on the formation of ∑PAH4. Zataria multiflora essential oil was observed to exert an inhibitory effect on the production of ∑PAH4. The saffron infusion demonstrated a reduction in impact at lower concentrations, while increased effectiveness was observed at higher concentrations. Additionally, a sample meeting the desired specifications, containing 18.5 % fat, 0.008 % saffron infusion, and 0.02 % ZMEO, was prepared with consideration of two dependent responses. The desirability of this sample was quantified at 0.72. The sample contained 2.20 ng g−1 of ∑PAH4 and was rated as acceptable by sensory analysis, with a score of 84.60 out of 100. All samples exhibited a margin of exposure (MOE) exceeding 100,000, indicating that there is minimal cause for concern. The incremental lifetime cancer risk (ILCR) for the samples with 10 % fat, 0.05 % saffron infusion, and 0.02 % ZMEO, as well as for the sample with 10 % fat, 0 % saffron infusion, and 0.01 % ZMEO, was found to be negligible. The assessment of overall quality is contingent upon the evaluation of fat content. In conclusion, the integration of effective variables can result in a sample that exhibits satisfactory organoleptic characteristics while simultaneously reducing the concentration of PAHs.

Evaluation of Different Cooking Methods to Control the Formation of Polycyclic Aromatic Hydrocarbons (PAHs) During Heat Treatment

Evaluation of Different Cooking Methods to Control the Formation of Polycyclic Aromatic Hydrocarbons (PAHs) During Heat Treatment

Electrochamical CO2 Reduction Characteristics with Various Copper-Based Alloy Plating Electrodes

Climate change caused by global warming has led to disasters in many countries around the world. The Sustainable Development Goals (SDGs) call for "taking specific measures against climate change." The time has come for humanity to think concretely about ways to suppress the increase in greenhouse gases, which ate thought to be the cause of global warming, and to actually implement them. Among the known greenhouse gases, carbon dioxide (CO2) accounts for about 75% and is recognized as an important target. Various efforts have already been made to reduce CO2 emissions. On the other hand, in order to reduce the amount of CO2 emitted into the atmosphere, technologies for geological storage and conversion of CO2 are indispensable. CO2 becomes a resource if it can be converted into useful industrial resources such as carbon monoxide, formic acid, or hydrocarbons in processes that utilize surplus or renewable energy. Many electrochemical reduction techniques have been studied for CO2 conversion, and Dr. Yoshio Hori has conducted a comprehensive study of electrochemical reduction of CO2 using metal electrocatalysts1). It has been clarified that the products are different depending on the metal species, and studies are underway to change the surface morphology and crystal planes of metal electrodes and to combine multiple metals in metal electrocatalysts. These previous studies were to reveal that the adsorption strength of CO2 and electrodes is based on the metal type of the electrode, and that changing the electrode metal changes the path, efficiency, and products of the electrochemical reduction reaction.The object of this research is to take a bird's-eye view of the characteristics of CO2 electrochemical reduction using copper-based alloy plating electrodes, which we have been development. Among metal electrodes, copper, which can produce hydrocarbons, has been the most widely studied for CO2 electrochemical reduction. When a copper-cobalt electrode is prepared by alloy plating, the ratio of the hydrocarbons, methane and ethylene, changes depending on the mixing ratio of cobalt. In this copper-cobalt electrode, cobalt exists as a substituted solid solution in the copper crystal structure, and it is considered that the generation efficiency of ethylene is reduced and that of methane is increased due to the inhibition of C-C bonding.When copper-tin electrodes are prepared by alloy plating, unlike cobalt, a solid solution or an intermetallic compound may be formed depending on the ratio of copper and tin. Since the atomic radii of tin atoms are quite different from those of copper atoms, tin atoms do not exist only in substituted solid solution as in the case of cobalt, but their crystal structure changes. The reduction properties of CO2 electrochemical reduction at a copper-tin electrode were changed. Copper produces hydrocarbons and tin produces formic acid as the main products of CO2 electrochemical reduction, while carbon monoxide is produced as the main product at a copper/tin ratio of 87:13.Computational chemistry studies predict that the formation of hydrocarbons by copper is via the two-electron reduction product carbon monoxide. The presence of tin near the copper atoms is considered to weaken the adsorption between copper and carbon monoxide. The modeling of the adsorption and the attempt to elucidate the cause by computational science revealed that the tin atoms are weakly bonded to the reaction intermediates and act only as the active sites for the formation of formic acid. It was found that the copper atom weakens the bond with carbon monoxide due to the presence of the tin atom next to the copper atom, and that it decreases the amount of adsorption of hydrogen and carbon monoxide. It is reported that the amount of carbon monoxide adsorbed on copper atoms is important for the formation of hydrocarbons, which is stabilized by the formation of hydrogen bonds with CHO*, the reaction intermediate to hydrocarbons. These results suggest that the adsorbed carbon monoxide is destabilized, and carbon monoxide is desorbed from the copper atom, resulting in an increase in carbon monoxide as a product.

(Invited) Novel Nitrogen and Sulfur Doped Colloid Imprinted Carbons (CICs) As Catalysts for Electrochemical CO2 Reduction

Electrochemical carbon dioxide (CO2) reduction represents a promising strategy for transforming this ubiquitous greenhouse gas into valuable commodities. Moreover, it offers a solution for storing intermittent renewable electricity by converting CO2 to chemical fuels. Unlike the formation of hydrocarbons, the reduction of CO2 to carbon monoxide (CO) involves only two electron/proton transfers, making it a less complex process. Also, CO is a very useful product as it can be used as a crucial feedstock for the production of fuels via the catalytic Fischer-Tropsch process. Nevertheless, the electrocatalytic conversion of CO2 to CO, carried out typically at metals, experiences significant challenges due to changing morphology with time, poor CO2RR product selectivity, and unavoidable competition with the hydrogen evolution reaction in aqueous environments.Therefore, attention has also been extended to CO2RR at carbon-based catalysts, as carbon possesses a plethora of inherent advantages, including its customizable and stable porous structures, high surface area, low cost, and environmental friendliness. While these properties make carbon highly favorable as a catalyst, it is inactive towards CO2 reduction in its pure state and must be doped or surface modified to achieve reasonable CO2RR kinetics. As an example, nitrogen-doped carbons (N-C) have shown acceptable activity towards the CO2RR,[1] attributed to the electronic modulation of conjugated sp2 carbon atoms by adjacent nitrogen dopants, disrupting electroneutrality by delocalizing π-orbital electrons within the carbon framework and creating active sites for CO2 activation. Even so, as N-C catalysts require significant overpotentials to attain satisfactory reaction rates and as the Faradaic efficiencies can be low and unstable, there is a pressing need to devise novel strategies to enhance the catalytic efficacy of N-C materials and achieve highly efficient CO2-to-CO conversion.To overcome these limitations, a dual-doping approach has been suggested, with the observed enhancement in activity of co-doped catalysts (e.g., N and sulfur) generally attributed to synergistic effects between nitrogen and the secondary atoms.[2] Computational simulations have predicted that the inclusion of sulfur into N-graphene could increase the asymmetrical spin density of the carbon system due to the higher polarizability of sulfur atoms compared to nitrogen and carbon atoms, thereby leading to improved catalytic performance. Moreover, sulfur modification can offer a potentially effective avenue for enhancing CO2RR performance over N-C materials by leveraging the electronic contribution from sulfur.[3] However, to the best of our knowledge, there are limited reports on the implementation of sulfur decoration strategies for electrocatalytic CO2RR.Our team has been working on a family of fully tunable monodisperse mesoporous carbon sheets, designated as nanoporous carbon scaffolds (NCS), along with colloid imprinted carbon (CIC) powders as carbon support materials. The CIC and NCS materials possess identical ordered monodisperse pore diameters, selected to be anywhere between 10 and 100 nm. These mesoporous carbons present numerous advantages compared to microporous carbons, notably their internal accessibility to solutions and gases, as well as their highly defective surfaces, making them easily modified. Specifically, the NCS offers additional benefits due to its self-supported nature and suitability for conducting fundamental CO2RR membrane electrode assembly (MEA) studies. To date, we have successfully N-doped both the CICs and the NCS and are now moving towards co-doping with S. N-doping has been achieved by subjecting the carbons to an NH3 atmosphere at 800 °C and S-doping is carried out by heat treatment of a mixture of the carbons and benzyl disulfide in Ar. We are also investigating a carbon precursor having intrinsic N and S content to simplify the preparation steps. In this case, the N,S-C catalysts were prepared by ball milling of dry silica particles (85 nm) and Alberta-sourced mesophase pitch. Subsequently, the mixture underwent carbonization at 900 °C for 2 hours, followed by removal of silica using a NaOH solution to yield the final product. CO2RR testing of these first generation of N,S doped catalysts has been carried out primarily in CO2-saturated bicarbonate solutions in an H-cell, giving an impressive CO Faradaic efficiency of 80% at overpotentials of only 390 mV and maintaining their stability for many hours of polarization. XPS studies are underway to establish a correlation between S, N content and speciation with the electrocatalytic activity and durability of these materials, with CO2RR testing also being carried out under flow conditions for comparison. Acknowledgements We would like to thank Momentum Materials Solution (Calgary) for providing the mesophase pitch. This work was supported by NSERC and CANSTOREnergy. References Wu, J., et al., ACS nano, 2015. 9(5).Duan, X., et al., Advanced Materials, 2017. 29(41).Pan, F., et al., Applied Catalysis B: Environmental, 2019. 252.

Electrodeposition of Cu with Amino Acids Toward Electrocatalytic Enhancement of CO₂ Reduction Reactions

The electrochemical reduction of carbon dioxide (CO2) is attracting technology because it can convert CO2 into a useful resource with zero emissions by using surplus electricity and renewable energy. For achieving efficient electrolysis of CO2, the development of a high performance electrocatalysts is required. Copper (Cu) is the only metal that is capable of electrochemically converting CO2 to hydrocarbons, but the high overpotential of hydrocarbon formation and the low selectivity of the reduction products have been problems. One of the solutions to these problems is the hybridization of metal and organic materials, in which the metal serves as the CO2 reduction reaction sites and the organic material stabilizes the intermediates [1]. In this study, we have electrodeposited Cu with five different types of amino acids which is expecting stabilization of CO2 reductive intermediates and evaluated its catalytic activity of electrochemical reduction of CO2.The electrodeposited Cu with amino acids was obtained by a constant current electrolysis at -2.0 mA cm-2 for 1.0 C cm-2 from the aqueous solutions containing 10 mmol dm-3 CuSO4･5H2O, 0.1 mol dm-3 Na2SO4, and 1.0 mmol dm-3 amino acids in a three-electrode cell with carbon paper (CP) as the working electrode, platinum wire as the counter electrode, and Ag/AgCl as the reference electrode. The pH of electrolytic bath was fixed at 1.10 by adding H2SO4. The obtained electrodeposited Cu samples were characterized by Raman measurement, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray spectroscopy (EDS) measurement, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical reduction of CO2 has been conducted by a constant potential electrolysis at -1.27 V vs. RHE of 0.5 mol dm-3 KHCO3 aqueous solutions saturated with CO2. The amount of reductive gas products was quantified by gas chromatograph- mass spectrometer (GC-MS) and gas chromatograph thermal conductivity detector (GC-TCD).The chronopotentiograms obtained during the electrodeposition of Cu, both in the presence and absence of 1.0 mmol dm−3 of the various amino acids showed different potential required to reach a current of −4.0 mA depending on the amino acids. However, considering the result of the open-circuit-potential measurement, the amino acids do not form complexes with Cu2+, suggesting that the electrolysis species remain consistent regardless of the amino acid present in the Cu electrodeposition bath. Therefore, the differences observed in the chronopotentiograms during Cu electrodeposition are attributed to the adsorption of amino acids on the electrodeposited Cu. The adsorption of amino acids on electrodeposited Cu was confirmed by Raman spectra and EDS spectra obtained from cross-sectional HAADF-STEM images. The peak of Raman spectra originating from amino acids was observed from electrodeposited Cu when Cu electrodeposition was conducted with amino acids, confirming the higher ratio of N and Cu on the surface compared to within the particle in the EDS spectra. Surface morphologies were observed by using SEM. CP has fiber-like structure but electrodeposited Cu without and with amino acids were deposited such coating CP fiber. The particle size of electrodeposited Cu with amino acids was more homogeneous, and the particles were more densely packed together than pure electrodeposited Cu. However, changing diffraction patterns and peak broadening due to loading amino acids in XRD were not observed.The electrochemical reduction of CO2 on electrodeposited Cu samples was performed and the faradic efficiency (FE) of the CO2 reduction gas products were calculated. All electrodeposited Cu with and without amino acids showed a higher FE for the electrochemical reduction of CO2 to CH4 compared to Cu foil (24.2%) and different values depending on amino acids. In particular, electrodeposited with L-histidine containing imidazole groups showed a high FE of 67.6%, effectively suppressing the hydrogen evolution reaction. This finding highlights the important role of functional groups in amino acids, especially imidazole, in facilitating the electrochemical conversion of CO2 to CH4. This study shows that certain functional groups in amino acids have a crucial influence on the catalytic efficiency of electrodeposited Cu in CO2 reduction reaction applications.[1] S. Jia et al., Angew. Chem. Int. Ed. 2021, 60, 10977–10982.

Oxide-Metal Transition Processes of CuxO Foams during CO2RR Probed by Operando Quick-XAS

Electrochemical CO2 reduction reaction (CO2RR) is a promising alternative for large-scale production of hydrocarbons. However, there are still some challenges including poor product selectivity and highly complex multiple-step reaction mechanisms.[1,2] To enhance the electrochemically active surface area and create more active surface sites, one of the promising approaches is the use of partial or complete (surface) oxidation of nanostructured copper materials. These Cu oxide precursor catalyst materials are not stable during the cathodic potentials applied for CO2RR, but still show an enhanced selectivity for the formation of C2+ products.[3,4] Interestingly, few studies proposed that oxygen can be present under CO2RR conditions in a few nm thick amorphous copper layer, while DFT calculations indicate that no subsurface oxygen remains thermodynamically stable at these highly cathodic potentials.[5-7] So far, only Valesco-Vélez et al. studied the Cu oxidation state changes (Cu2+ and Cu+ to metallic Cu) during CO2RR in CO2-saturated 0.1 M KHCO3 probed by operando X-ray absorption spectroscopy (XAS).[8] However, for pure CuO no reduction to metallic copper or Cu2O even at highly cathodic conditions is found, due to the formation of a copper carbonate passivation layer.[8] Thus, it is still poorly understood how the structure of the Cu/CuxO precursor materials and their simultaneous reduction processes to metallic copper influence the CO2RR product distribution and the overpotential required for hydrocarbon formation. Recently, we have shown the critical potential of oxide-metal transition processes for a Cu oxide foam annealed at 300 °C in air probed by operando XAS, X-ray diffraction (XRD), and Raman spectroscopy techniques.[9,10]Using Cu K-edge Quick-XAS technique, we aim to understand the potential-dependent reduction of different Cu2+:Cu+ ratios to Cu0 for nanoporous CuxO foam precursor catalysts under CO2RR conditions. The CuxO foams were prepared by electrodeposition and subsequent thermal annealing between 100 and 450 °C in air to generate the different Cu2+:Cu+:Cu0 ratios. Initially, from ex-situ XANES, XRD, and XPS analyses, we found that a rise in annealing temperature leads to an increase in the proportion of Cu2+ species and their degree of crystallinity within the CuxO foams. After annealing at 100 °C and 200 °C, the CuO phase/species are amorphous and mainly found at the surface of the foam. Once the annealing temperature reaches 300 °C or higher, the CuO phase is entirely crystalline.With these different chemical states of the precursor catalyst, the Cu oxide-metal transition kinetics during cathodic potential increment (ΔE = 100 mV), step (ΔE > 100 mV), and jump (ΔE > 500 mV) experiments in CO2-saturated 0.5 M KHCO3 were comprehensively investigated using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) and Linear Combination Fit (LCF) analyses of the operando Cu K-edge Quick-XANES data. Our results demonstrate that different oxide-metal transition kinetics were found strongly dependent on the initial abundance of Cu2+ species and precursor structure (ordered vs. amorphous) as well as on the applied potential protocol to the CuxO foam precursor catalysts. More precisely, a high initial population of crystalline CuO, which is found for the CuxO foams annealed at 300 °C and 450 °C, leads to a significant shift of the oxide-metal transition potential towards lower cathodic overpotentials. For example, for the CuxO foam annealed at 450 °C (rich in crystalline CuO phases) the oxide-metal transition potential is shifted to 0 VRHE, while for the foam annealed at 100 °C this transition occurs at – 0.6 VRHE. Furthermore, smaller potential increments increase the formation and accumulation of Cu+ species, thereby slowing down the reduction kinetics. For the CuxO foam annealed at 200 °C, we could observe a full reduction to metallic Cu if jumping from OCP directly to – 0.5 VRHE, whereas no full reduction took place if using incremental potentials before applying – 0.5 VRHE.Overall, we show the substantial influence of crystalline CuOand the applied potential protocol on the reduction of CuxO foam precursor materials to metallic Cu during CO2RR.

Kinetics of formation of individual C1-C5 hydrocarbons during stepwise dry pyrolysis of kerogen from Domanik shale after hydrothermal treatment

Kinetics of formation of individual C1-C5 hydrocarbons during stepwise dry pyrolysis of kerogen from Domanik shale after hydrothermal treatment

Chemical structure analysis of chitosan-modified road bitumen after de-icing salt treatment

Asphalt pavements are constantly exposed to many destructive environmental factors including de-icing salts. The problem of the negative effect of salt ions on the performance and consequently the durability of road pavements occurs mainly in temperate climates and regions directly neighboring saline water areas. The salt ions react chemically with the bitumen components, which consequently changes their electronic structure and results in a weakening of the intermolecular interactions occurring between them. Therefore, this study focused primarily on an investigation into the potential for inhibiting the destructive erosion process of bitumen by its modification with chitosan. Studies involving changes in the acidity of the eroding solution as well as chemical and surface properties of the eroded bitumen were carried out for three different salts (NaCl, MgCl2, CaCl2) at varying concentrations, i.e. 5%, 10%, 15% (w/w) after 7 and 28 days of erosion process. Main findings demonstrate that chitosan prevents negative changes in the bitumen physico-chemical properties occurring during the salt erosion process. This effect is especially visible for the bitumen eroded with a solution of MgCl2 and CaCl2. For these salts, chitosan biopolymer reduces the introduction of Cl− ions into the bitumen-building hydrocarbon structures and formation of C–Cl bonds, which is demonstrated by a reduction in the pH changes of the eroding solutions. In addition, chitosan biopolymer inhibits leaching of organic matter from the bitumen, prevents C = O groups formation and reduces the negative effects of de-icing salts on the cohesion energy of the bitumen.

Upcycling Polyethylene to High-Purity Hydrogen under Ambient Conditions via Mechanocatalysis.

Polyethylene (PE) is the most abundant plastic waste, and its conversion to hydrogen (H2) offers a promising route for clean energy generation. However, PE decomposition typically requires high temperatures due to its strong chemical bonds, leading to significant carbon emissions and low H2 selectivity (theoretically less than 75 vol % after accounting for further steam-reforming reactions). Here, we report a mechanocatalytic strategy that upcycles PE into high-purity H2 (99.4 vol %) with an exceptional H2 recovery ratio of 98.5 % (versus 15.7 % via thermocatalysis), using manganese as a catalyst at a low temperature of 45 °C. This method achieves a reaction rate 3 orders of magnitude higher than thermocatalysis. The marked improvement in H2 recovery ratio is mainly due to metal carbides formation induced by the mechanocatalytic process, which does not catalyze hydrocarbons formation. This work is expected to advance studies of the conversion of polyolefins to high-purity H2 with net-zero carbon emissions.

Inhibition of Polycyclic Aromatic Hydrocarbons Formation During Supercritical Water Gasification of Sewage Sludge by H2O2 Combined with Catalyst

This work evaluated the alterations in the levels and types of polycyclic aromatic hydrocarbons (PAHs) within both liquid and solid products throughout the process of the catalytic supercritical water gasification of dewatered sewage sludge to examine the catalytic effect of various catalysts and the inhibit reaction pathways. The addition of Ni, NaOH, Na2CO3, H2O2, and KMnO4 reduced the concentrations of PAHs, with Ni and H2O2 showing the best performance. The concentrations of PAHs, especially higher-molecular-weight compounds in the residues, decreased sharply as the H2O2 amount increased. At a 10 wt% H2O2 addition, the levels of PAHs in the liquid and solid products were reduced by 91% and 88%, respectively. High-ring PAHs were not detected in the residues as the H2O2 amount increased to an 8 wt%. H2O2 addition evidently inhibits PAH formation by promoting the ring-opening reactions of initial aromatic compounds in raw sludge and inhibiting the polymerization of open-chain intermediate products. The addition of NaOH + H2O2 or Ni + H2O2 as combined catalysts significantly lowered PAH concentrations while increasing the H2 yield. The addition of 5 wt% Ni + H2O2 reduced PAH concentrations in the liquid and solid residues by 70% and 44%, respectively, while the H2 yield escalated from 0.13 mol/kg OM to 3.88 mol/kg OM. Possible mechanisms associated with the reaction pathways of these combined catalysts are proposed.

Upcycling Polyethylene to High‐Purity Hydrogen under Ambient Conditions via Mechanocatalysis

Polyethylene (PE) is the most abundant plastic waste, and its conversion to hydrogen (H2) offers a promising route for clean energy generation. However, PE decomposition typically requires high temperatures due to its strong chemical bonds, leading to significant carbon emissions and low H2 selectivity (theoretically less than 75 vol% after accounting for further steam‐reforming reactions). Here, we report a mechanocatalytic strategy that upcycles PE into high‐purity H2 (99.4 vol%) with an exceptional H2 recovery ratio of 98.5% (versus 15.7% via thermocatalysis), using manganese as a catalyst at a low temperature of 45 °C. This method achieves a reaction rate 3 orders of magnitude higher than thermocatalysis. The marked improvement in H2 recovery ratio is mainly due to metal carbides formation induced by the mechanocatalytic process, which does not catalyze hydrocarbons formation. This work is expected to advance studies of the conversion of polyolefins to high‐purity H2 with net‐zero carbon emissions.