Simple Organic Molecules Research Articles

Efficient and Robust Ab Initio Self-Consistent Field Acceleration Algorithm Based on a Semiempirical Model Hamiltonian.

A novel doubly iterative self-consistent field (SCF) approach using a semiempirical model Hamiltonian (denoted as the SMH algorithm) is proposed to accelerate the Hartree-Fock (HF) and density functional theory (DFT) calculations. This method first constructs the Fock matrix exactly in each SCF macroiteration, followed by a few SCF microiterations, where the Fock matrix is incrementally updated using an inexpensive semiempirical approximation. This leads to an improved wave function in each SCF macroiteration with minimal additional cost, and therefore a reduced number of exact Fock builds is required for SCF convergence. The SMH algorithm can be combined with conventional SCF convergence techniques such as level shifting, direct inversion in the iterative subspace (DIIS), and energy-DIIS (EDIIS). When integrated with DIIS, SMH enhances the convergence of simple organic molecules by approximately 10% compared to plain DIIS, with speedups of up to 60% for the more challenging transition metal systems compared to EDIIS + DIIS. Our results show that SMH is a reliable SCF accelerator that seldom deteriorates convergence and is highly robust.

Stable carbon isotope evolution of formaldehyde on early Mars

Organic matter in the Martian sediments may provide a key to understanding the prebiotic chemistry and habitability of early Mars. The Curiosity rover has measured highly variable and 13C-depleted carbon isotopic values in early Martian organic matter whose origin is uncertain. One hypothesis suggests the deposition of simple organic molecules generated from 13C-depleted CO derived from CO2 photochemical reduction in the atmosphere. Here, we present a coupled photochemistry-climate evolution model incorporating carbon isotope fractionation processes induced by CO2 photolysis, carbon escape, and volcanic outgassing in an early Martian atmosphere of 0.5–2 bar, composed mainly of CO2, CO, and H2 to track the evolution of the carbon isotopic composition of C-bearing species. The calculated carbon isotopic ratio in formaldehyde (H2CO) can be highly depleted in 13C due to CO2-photolysis-induced fractionation and is variable with changes in atmospheric CO/CO2 ratio, surface pressure, albedo, and H2 outgassing rate. Conversely, CO2 becomes enriched in 13C, as estimated from the carbonates preserved in ALH84001 meteorite. Complex organic matter formed by the polymerization of such H2CO could explain the strong depletion in 13C observed in the Martian organic matter. Mixing with other sources of organic matter would account for its unique variable carbon isotopic values.

(Invited) Development of Multifunctional Nanoscale Reactors for Electrocatalytic Oxidation of Dimethyl Ether Fuel

There has been growing interest in utilizing small (simple) organic molecules, as alternative fuels to hydrogen, for electrochemical energy conversion in fuel cells. Dimethyl ether (DME) is one of the possible choices in this respect. But electrooxidation of DME is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.Bimetallic PtSn catalysts were found to be almost as active as PtRu for methanol oxidation, and PtSn was even more efficient toward the electrooxidation of ethanol where breaking of C-C bond is required. While PtRu forms a single-phase homogeneous (intermetallic) alloy in which Ru is largely metallic, tin does not maintain its metallic state in PtSn (heterogenous alloy) and is transformed readily to such oxygenated species as Sn oxides or hydroxides. During operation of PtSn, the Pt component retains its mostly metallic character and act independently as Pt0 catalyst. By analogy to Ru, the Sn “bifunctional agent” tends to activate the water dissociative adsorption and increases population of chemisorbed hydroxyl groups to diminish the Pt-poisoning effect through enhanced oxidation of CO-type intermediates. Nevertheless, the DME oxidation on both PtRu or PtSn is still kinetically less favorable, relative to the systems’ performance toward methanol. While Sn, and particularly Ru alloyed atoms activate readily the water dissociative adsorption on Pt and permit the oxidative stripping of the poisoning CO-type adsorbates, the feasibility of the enhancement of the of the DME adsorption and activation through alteration of the electronic structure of Pt catalytic sites has not been fully explained. By analogy to the ethanol oxidation, Pt sites in the heterogeneous PtSn alloy are active toward dissociation of the DME molecule but the Sn additive is less efficient than Ru (from intermetallic PtRu) in the oxidative removal of poisoning adsorbates. But PtRu is probably the most active during oxidation of methanol, and this small organic molecule is also the DME-oxidation-reaction intermediate. Nevertheless, in comparison to bare Pt, electrooxidation of DME starts at PtRu and PtSn at less positive potentials.We pursue a concept of utilization of multicomponent hybrid electrocatalytic systems or nanoreactors utilizing zirconia oxide matrices for supporting and activation of primarily PtSn nanoparticles supported onto Vulcan XC-72 carbon black carriers. Electrocatalytic activity of Vulcan-supported PtSn (PtSn/V) nanostructured alloys supported onto ZrO2 matrices has been significantly enhanced toward electrooxidation of DME in acid medium (0.5 mol dm-3 H2SO4) by decorating PtSn/V with bimetallic PtRu nanoparticles. The enhancement effect concerns both shifting the onset potential for the DME-oxidation toward less positive values and increase of the DME electrocatalytic current densities recorded under both cyclic voltammetric and chronoamperometric conditions. The activating capabilities of ruthenium nanostructures seem to originate from the existence (even below 0.45 V vs. RHE) of reactive ruthenium oxo/ hydroxo groups on their surfaces capable of inducing the oxidative removal of poisoning (CO-type) adsorbates from the neighboring platinum catalytic sites. In this respect, the Ru-oxo species seem to support activity of Sn forming with Pt the PtSn heterogenous alloy. The PtSn/V admixed with PtRu decorated ZrO2 exhibit very high activity toward the oxidation of methanol which is also an important DME-oxidation intermediate. On the whole, the hybrid materials composed of Vulcan-supported PtSn decorated with Ru or PtRu nanoparticles decorated zirconia oxide seem to act as multifunctional nanoreactors inducing not only stripping of poisoning adsorbates but also catalyzing oxidation of the DME-reaction intermediates (methanol). Acknowledgement Authors acknowledge financial support of the National Science Center (Poland) under Opus Project 2018/29/B/ST5/02627.

A Prebiotic Pathway to Nicotinamide Adenine Dinucleotide.

Enzymes play a fundamental role in cellular metabolism. A wide range of enzymes require the presence of complementary coenzymes and cofactors to function properly. While coenzymes are believed to have been part of the last universal ancestor (LUCA) or have been present even earlier, the syntheses of crucial coenzymes like the redox-active coenzymes flavin adenine dinucleotide (FAD) or nicotinamide adenine dinucleotide (NAD+) remain challenging. Here, we present a pathway to NAD+ under prebiotic conditions starting with ammonia, cyanoacetaldehyde, prop-2-ynal and sugar-forming precursors, yielding in situ the nicotinamide riboside. Regioselective phosphorylation and water stable light activated adenosine monophosphate derivatives allow for topographically and irradiation-controlled formation of NAD+. Our findings indicate that NAD+, a coenzyme vital to life, can be formed non-enzymatically from simple organic feedstock molecules via photocatalytic activation under prebiotically plausible early Earth conditions in a continuous process under aqueous conditions.

Multiple stimuli-responsive low-molecular-weight organogel with room temperature phosphorescence for dynamic anti-counterfeiting

Pure organic luminogens with stimuli-responsive room temperature phosphorescence (RTP) have drawn much attention due to their promising applications in dynamic anti-counterfeiting. In this work, we designed a simple organic molecule with rigid chemical structure (m-FBCM), and all-atom molecular dynamics simulation indicated that it was a potential organogelator. Moreover, the molecule comprises multiple carbonyl units and aromatic rings, which could promote the intersystem crossing process. Our experiments revealed that m-FBCM could form stable gel in DMSO, promoted by balanced intermolecular π-π interactions. Green afterglow was observed at room temperature in the gel state with lifetime 41.6 ms, ascribed to its RTP. The afterglow became invisible at 45 °C and could recover upon cooling to room temperature. Moreover, the N-acylation reaction between m-FBCM xerogel and vapor of volatile primary amine could occur in a few minutes without additional catalyst, providing an orange afterglow. The thermal-responsive and chemical-reponsive properties impart the RTP gel promising application in dynamic anti-counterfeiting.

Hierarchical organic microspheres from diverse molecular building blocks

Microspherical structures find broad application in chemistry and materials science, including in separations and purifications, energy storage and conversion, organic and biocatalysis, and as artificial and bioactive scaffolds. Despite this utility, the systematic diversification of their morphology and function remains hindered by the limited range of their molecular building blocks. Drawing upon the design principles of reticular synthesis, where diverse organic molecules generate varied porous frameworks, we show herein how analogous microspherical structures can be generated under mild conditions. The assembly of simple organic molecules into microspherical structures with advanced morphologies represents a grand challenge. Beginning with a partially condensed Schiff base which self-assembles into a hierarchical organic microsphere, we systematically synthesized sixteen microspheres from diverse molecular building blocks. We subsequently explicate the mechanism of hierarchical assembly through which these hierarchical organic microspheres are produced, isolating the initial monomer, intermediate substructures, and eventual microspheres. Furthermore, the open cavities present on the surfaces of these constructs provided distinctive adsorptive properties, which we harnessed for the immobilization of enzymes and bacteriophages. Holistically, these hierarchical organic microspheres provide an approach for designing multi-functional superstructures with advanced morphologies derived from simple organic molecules, revealing an extended length scale for reticular synthesis.

A Fusion-Growth Protocell Model Based on Vesicle Interactions with Pyrite Particles.

Protocell models play a pivotal role in the exploration of the origin of life. Vesicles are one type of protocell model that have attracted much attention. Simple single-chain amphiphiles (SACs) and organic small molecules (OSMs) possess primitive relevance and were most likely the building blocks of protocells on the early Earth. OSM@SAC vesicles have been considered to be plausible protocell models. Pyrite (FeS2), a mineral with primitive relevance, is ubiquitous in nature and plays a crucial role in the exploration of the origin of life in the mineral-water interface scenario. "How do protocell models based on OSM@SAC vesicles interact with a mineral-water interface scenario that simulates a primitive Earth environment" remains an unresolved question. Hence, we select primitive relevant sodium monododecyl phosphate (SDP), isopentenol (IPN) and pyrite (FeS2) mineral particles to build a protocell model. The model investigates the basic physical and chemical properties of FeS2 particles and reveals the effects of the size, content and duration of interaction of FeS2 particles on IPN@SDP vesicles. This deepens the understanding of protocell growth mechanisms in scenarios of mineral-water interfaces in primitive Earth environments and provides new information for the exploration of the origin of life.

Experimental and theoretical aspects of magnetic circular dichroism and magnetic circularly polarized luminescence in the UV, visible and IR ranges: A review

A historical sketch of the MCD (magnetic circular dichroism) spectroscopy is reported in its experimental and theoretical aspects. MCPL (magnetic circularly polarized luminescence) is also considered. The main studies are presented encompassing porphyrinoid systems, aggregates and materials, as well as simple organic molecules useful for the advancement of the interpretation. The MCD of chiral systems is discussed with special attention to new studies of natural products with potential pharmaceutical valence, including Amaryllidaceae alkaloids and related isocarbostyrils. Finally, the vibrational form of MCD, called MVCD, which is recorded in the IR part of the spectrum is also discussed. A final brief note on perspectives is given.

An Exceptional Valorization of CuO Nanoparticles in Ionic Liquids as an Efficient Medium for the Electrophilic Substitution of Indole Towards the Formation of Bis(indolyl)methanes

Aim: Ionic liquids are promising green solvents with simple but unique structure-related physical properties such as negligible vapour pressure, exceptional thermal conductivity, remarkable thermal stability and their suitability and inertness towards a broad range of catalytic applications. CuO NPs have been addressed as a cost-effective and a reagent of a choice that necessitates only mild reaction conditions to offer a high yield of the desired products with exceptional selectivity in a short duration of time. Therefore, in the present work, attempts have been made to explore the catalytic potentials of CuO NPs in an ionic liquid medium to synthesize biologically important bis(indolyl)methanes. Background: Catalytic explorations of metal oxide nanoparticles in ionic liquids offers a cooperative effect that has a significant impact on the kinetics as well as on the outcome of the reaction. Therefore, such catalytic systems in the present times have seized the scientific community's interest from the perspectives of sustainable development in synthetic organic chemistry. The combination of metal oxide nanoparticles with highly tunable ionic liquids is not only used to synthesize simple organic molecules but also explored in the synthesis of complex organic molecules of high commercial and biological relevance. Objectives: The current work offers a rapid and robust protocol for synthesizing bis(indolyl)methanes via electrophilic substitution reaction between indole and various aldehydes in the presence of a CuO nanoparticles-ionic liquid system. The discussion focuses on the high tolerance of different functionalities by the catalytic system leading to the synthesis of bis(indolyl)methanes. Methods: CuO NPs have been synthesized via the co-precipitation method using ionic liquid. The applicability of metal oxide nanoparticles-IL matrix was further investigated in synthesizing bis(indolyl)methanes. Results: The FT-IR absorption below 600 cm-1 and the XRD pattern showing all the peaks in the diffraction diagram revealed the formation of CuO NPs. FESEM images show the flake-shaped morphology of CuO NPs and are found to be separated from the agglomerated clusters Conclusion: Ionic liquid-CuO NPs matrix reveals good to exceptional catalytic properties, and their advancements as a catalytic system at room temperature open new avenues for synthetic organic chemists.

Modulating solvated structure of Zn2+ and inducing surface crystallography by a simple organic molecule with abundant polar functional groups to synergistically stabilize zinc metal anodes for long-life aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have attracted significant attention owing to their inherent security, low cost, abundant zinc (Zn) resources and high energy density. Nevertheless, the growth of zinc dendrites and side reactions on the surface of Zn anodes during repeatedly plating/stripping shorten the cycle life of AZIBs. Herein, a simple organic molecule with abundant polar functional groups, 2,2,2-trifluoroether formate (TF), has been proposed as a high-efficient additive in the ZnSO4 electrolyte to suppress the growth of Zn dendrites and side reaction during cycling. It is found that TF molecules can infiltrate the solvated sheath layer of the hydrated Zn2+ to reduce the number of highly chemically active H2O molecules owing to their strong binding energy with Zn2+. Simultaneously, TF molecules can preferentially adsorb onto the Zn surface, guiding the uniform deposition of Zn2+ along the crystalline surface of Zn(002). This dual action significantly inhibits the formation of Zn dendrites and side reactions, thus greatly extending the cycling life of the batteries. Accordingly, the Zn//Cu asymmetric cell with 2 % TF exhibits stable cycling for more than 3,800 cycles, achieving an excellent average Columbic efficiency (CE) of 99.81 % at 2 mA cm−2/1 mAh cm−2. Meanwhile, the Zn||Zn symmetric cell with 2 % TF demonstrates a superlong cycle life exceeding 3,800 h and 2,400 h at 2 mA cm−2/1 mAh cm−2 and 5 mA cm−2/2.5 mAh cm−2, respectively. Simultaneously, the Zn//VO2 full cell with 2 % TF possesses high initial capacity (276.8 mAh/g) and capacity retention (72.5 %) at 5 A/g after 500 cycles. This investigation provides new insights into stabilizing Zn metal anodes for AZIBs through the co-regulation of Zn2+ solvated structure and surface crystallography.

Design and synthesis of simple quinoline-based organic molecules as dual/multifunctional chemosensors for the detection of Cu2+/Fe3+ ions

The current research deals with the sensitivity of a turn-on-off fluorescence chemosensor using the probe, namely (E)-2-(((2‑hydroxy-5-methylphenyl) imino)methyl) quinolin-8-ol (HQ-AMP) as a selective detection of Cu2+/Fe3+ ions in DMSO: H2O (1:1, v/v). The probe HQ-AMP was synthesized using a simple acid catalyst, Schiff base condensation, which involves the reaction between aldehyde and amine. This probe shows a significant fluorescence response towards Cu2+ and Fe3+ ions among the other alkaline earth metal ions. The HQ-AMP forms a 1:1 stoichiometry complex with a high binding constant for Cu2+ and Fe3+ ions with a low detection limit of 34 nM and 47 nM, respectively. Due to their strong intermolecular charge transfer properties, the probe HQ-AMP shows intense fluorescence at 488 nm upon excitation at 350 nm. The selective fluorescence quenching of probe HQ-AMP with Cu2+/Fe3+ ions shows static/dynamic quenching and their quenching constant of 1.93 × 10−8 and 2.06 × 10−8, respectively. Also, the probe shows the highest selectivity towards Cu2+/Fe3+ ions over the other tested metal ions.

Cation exchange to montmorillonite induces selective adsorption of amino acids

Concentrating simple organic molecules, such as amino acids, in the adsorbed phase could have been an early step in prebiotic evolution towards more complex bio-macromolecules on the early Earth. Smectite clay minerals represent potential selective sorbents for prebiotic molecules because of their negative structural charge and high surface area. This study evaluated the adsorption behavior of amino acids to montmorillonite, a well-characterized smectite, at varying pH and fluid compositions. At both pH 5 and 7 in a sodium chloride fluid, amino acids with basic sidechains (L-arginine and L-lysine), which are primarily cationic under these conditions, were selectively adsorbed to montmorillonite with Langmuir constants much greater than amino acids that were predominantly zwitterionic or anionic in solution. On average, the Langmuir constants for the cationic amino acids were 30 (pH 5) and 50 (pH 7) times greater than the constants for zwitterionic amino acids and 120 (pH 5) and 80 (pH 7) times greater than the constants for L-glutamic acid. Under the same pH conditions in a magnesium chloride solution, the adsorption of L-arginine and L-lysine was substantially inhibited with Langmuir constants ∼ 10 times smaller. These observations suggest that cation exchange is the dominant adsorption mechanism for amino acids on montmorillonite. X-ray diffraction and infrared spectroscopy indicate that L-arginine and L-lysine enter the smectite interlayer where the protonated amino sidechain has the strongest interactions with the mineral surface, further supporting adsorption driven primarily through electrostatic interactions. Therefore, smectites on the early Earth may have selectively concentrated cationic amino acids, providing a potential template for the polymerization of α-amine linked peptides.

Scaffolded Structure Determination Activities Utilizing 2D NMR Spectroscopy of Simple Organic Molecules

Scaffolded Structure Determination Activities Utilizing 2D NMR Spectroscopy of Simple Organic Molecules

Application of the synergistic Ti/SnO2–Sb–Cu anode and Ti/ZnO/CuO cathode in the electrochemical treatment of wastewater

The current research mostly focused on the single working electrode of anode for the treatment of wastewater. Therefore, a low-cost dual-electrode system using Ti/SnO2–Sb–Cu (TSSC) as the anode and Ti/ZnO/CuO (TZC) as the cathode was constructed for the synergistic treatment of methylene blue dye wastewater. Electrochemical analyses of the TSSC electrode show an ultra-high oxygen evolution potential of 2.2 V, the greater stability and the excellent corrosion resistance when compared with the traditional Ti/SnO2–Sb (TSS) electrodes. Hydroxyl radicals (•OH) are thought to be the main oxidants in the degradation process, the results show that the content of •OH of the TZC cathode is 57 % higher than that of ordinary inert electrode. Due to the synergistic effect of the two electrodes, the color of methylene blue can be quickly removed by 99 % in 20 min, and the highest chemical oxygen demand (COD) removal rate can reach 79.5 %. The optimal operation conditions were a pH of 4, a current density of 20 mA cm−2 and an initial concentration of 50 mg L−1. Finally, the degradation pathway of MB was investigated using GC-MS technique and UV absorption spectroscopy. The results suggest that the large organic molecules are continuously cleaved to produce simple aromatic hydrocarbons, which are then destroyed to simple minor organic molecules, ultimately oxidized to CO2 and H2O. This investigation suggests a new idea for the design of an efficient and cost-effective double electrode for the electrocatalytic degradation of dye wastewater.

Clustering triggered emissive liquid crystalline template for dual mode upconverted and downconverted circularly polarized luminescence.

Liquid crystalline materials have attracted significant attention in chiroptical research due to their ability to form long range ordered helical superstructures. Research focus has been on exploiting the unique properties of liquid crystalline materials to demonstrate highly dissymmetric circularly polarised luminescent (CPL) systems. In this study, we present a thermally driven, facile approach to fabricate CPL-active materials utilizing cholesteryl benzoate as the active substrate. Cholesteryl benzoate, a well-known thermotropic liquid crystal, has been found to manifest intriguing optical characteristics upon subjecting to repeated heating-cooling cycles. Despite the absence of conventional fluorescent moieties, the material exhibited luminescence through aggregation induced clustering triggered emission mechanism. Systematic investigations revealed excitation-dependent CPL for solid cholesteryl benzoate films when subjected to multiple thermal cycles. The excited state chiroptical investigation performed after multiple thermal cycles showed a luminescence anisotropy (glum) of 8 × 10-2, which is a high value for simple organic molecules. Moreover, upon co-assembly with lanthanide-based upconversion nanophosphors (UCNPs), the hybrid system demonstrated upconverted circularly polarised luminescence (UC-CPL). Benefiting from the ability to endow upconversion nanoparticles of various sizes, fabrication of UCNP-ChB hybrid nanocomposites exhibiting multicoloured upconversion CPL was demonstrated. These findings highlight the potential of liquid crystalline materials for diverse applications, including 3D optical displays and anticounterfeiting technologies.

Core-level spectroscopic probing of the heteromolecular H-bonding interaction in Cyanuric Acid/Melamine 2D networks

The preparation of complex molecular architectures routinely exploits the directionality and cooperative strength of hydrogen bonding interactions, which can be used for a reversible control of molecular self-assembly of simple organic molecules. Cyanuric acid (CA) and Melamine (M) are two such examples of simple organic molecules which can assemble in well-ordered two-dimensional networks on solid surfaces. Their CA*M adduct is a prototypical molecular system exhibiting two complementary NH••O and NH••N hydrogen bonds. In this work we exploit the initial state locality of K-shell core-electron excitation/ionization process to get a detailed information on the electronic structure modification which characterizes the long-range order of the heteromolecular H-bonding motif of the CA*M adduct as compared to the homomolecular CA and M extended structures. Both of N 1s X-Ray Photoelectron spectroscopy (XPS) and N K-shell Near Edge X-Ray Absorption Fine-Structure (NEXAFS) spectroscopy and are used to get complementary information on the prototypical CA*M heteromolecular system characterizing both the H-donor/H-acceptor nature of the molecular constituents and the extent of heteromolecular H-bond formation, due to the quenching of σ*(N–H) resonances.

Chemical evolution of primordial salts and organic sulfur molecules in the asteroid 162173 Ryugu

Samples from the carbonaceous asteroid (162173) Ryugu provide information on the chemical evolution of organic molecules in the early solar system. Here we show the element partitioning of the major component ions by sequential extractions of salts, carbonates, and phyllosilicate-bearing fractions to reveal primordial brine composition of the primitive asteroid. Sodium is the dominant electrolyte of the salt fraction extract. Anions and NH4+ are more abundant in the salt fraction than in the carbonate and phyllosilicate fractions, with molar concentrations in the order SO42− > Cl− > S2O32− > NO3− > NH4+. The salt fraction extracts contain anionic soluble sulfur-bearing species such as Sn-polythionic acids (n < 6), Cn-alkylsulfonates, alkylthiosulfonates, hydroxyalkylsulfonates, and hydroxyalkylthiosulfonates (n < 7). The sulfur-bearing soluble compounds may have driven the molecular evolution of prebiotic organic material transforming simple organic molecules into hydrophilic, amphiphilic, and refractory S allotropes.

Conformational analysis of simple oxygenated hydrocarbons in a solid parahydrogen matrix

Acetone, acetaldehyde, propylene oxide, propionaldehyde, and 2-propanol are all simple oxygen-containing organic molecules, and play an important role in combustion chemistry, atmospheric chemistry, and astrochemistry. These small molecules are often produced by chemical reactions or UV photolysis of larger molecules containing oxygen atoms. Thus, knowing the IR spectrum of these molecules is important for the identification of (photo)chemical processes of various molecules. In this study, the IR spectra of these five common organic molecules were studied using parahydrogen (pH2) matrix isolation with Fourier transform infrared spectroscopy. Conformational analysis of the IR spectra revealed two conformers of propionaldehyde and 2-propanol exist in the pH2 matrix at 3.8 K. This work will be useful for the identification of products in future pH2 photochemistry experiments.

Techno-Economic Analysis of Electrochemical Refineries Using Solid Oxide Cells for Oxidative Coupling of Methane

With the shift away from fossil resources, there is a need for alternative pathways to carbon-based commodities such as ethylene. The electrochemical oxidative coupling of methane (OCM) enables the synthesis of higher hydrocarbons from simple organic molecules i.e., methane and has the potential to replace conventional ethylene production in the future. However, current solid oxide OCM cell development is still in an early stage and more comprehensive system-level analyses are needed to better understand operating conditions and economics to guide research and development. For this purpose, process models and new integration strategies for the electrochemical OCM process were developed. The integration of the electrochemical OCM unit into the plant revealed to be challenging based on current solid oxide cell designs and will be discussed as part of this presentation. The performance of the OCM plant is benchmarked against current state-of-the-art ethane steam cracker plants. In this context, key performance metrics are efficiency, direct and indirect carbon dioxide emissions, power consumption, plant cost and cost of ethylene. Of particular interest are aspects of hydrogen co-production and carbon dioxide utilization as well as the impact of carbon dioxide emission factors from the grid, which have shown to be of particular importance for electrochemical processes. Moreover, critical aspects of heat integration will be discussed including fuel pre-heating, carbon deposition and thermal cell management. The analysis will provide new insights into economic cost driving factors and the impact of cell cost, current density, overpotentials and Faraday efficiency upon the cost of ethylene. Based upon this information, performance targets will be recommended that will allow electrochemical OCM to become economically competitive in a free market environment.

Structure and Reactivity of Metal-Oxide-Supported Noble Metal Nanoparticles: Electrooxidation of Simple Organic Molecules

There has been growing interest in utilizing small (simple) organic molecules, as alternative fuels to hydrogen, in electrochemical energy conversion systems. In addition to ethanol (biofuel), that can be ideally oxidized to carbon dioxide thus delivering twelve electrons, recent important systems include dimethyl ether as well. But realistically the respective reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium.We pursue a concept of utilization of mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of methanol, ethanol, formic acid and dimethyl ether. Among important issues is incorporation of Rh nanostructures capable of weakening, or even breaking, the C-C bond in the ethanol molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol is partitioned (at Rh) to methanolic residues further oxidized at PtRu cannot be excluded.