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Rigorous electrokinetic results are key to understanding the reaction mechanisms in the electrochemical CO reduction reaction (CORR), however, most reported results are compromised by the CO mass transport limitation. In this work, we determined mass transport-free CORR kinetics by employing a gas-diffusion type electrode and identified dependence of catalyst surface speciation on the electrolyte pH using in-situ surface enhanced vibrational spectroscopies. Based on the measured Tafel slopes and reaction orders, we demonstrate that the formation rates of C 2+ products are most likely limited by the dimerization of CO adsorbate. CH 4 production is limited by the CO hydrogenation step via a proton coupled electron transfer and a chemical hydrogenation step of CO by adsorbed hydrogen atom in weakly (7 < pH < 11) and strongly (pH > 11) alkaline electrolytes, respectively. Further, CH 4 and C 2+ products are likely formed on distinct types of active sites. Electrokinetic results are key to understanding the mechanisms in electrochemical CO reduction reaction. Here, the authors determine mass transport free kinetics using a gas-diffusion electrode and identified dependence of copper surface speciation on the electrolyte pH using in situ surface enhanced spectroscopies.

Harnessing renewable electricity to drive the electrochemical reduction of CO 2 is being intensely studied for sustainable fuel production and as a means for energy storage. Copper is the only monometallic electrocatalyst capable of converting CO 2 to value-added products, e.g., hydrocarbons and oxygenates, but suffers from poor selectivity and mediocre activity. Multiple oxidative treatments have shown improvements in the performance of copper catalysts. However, the fundamental underpinning for such enhancement remains controversial. Here, we combine reactivity, in-situ surface-enhanced Raman spectroscopy, and computational investigations to demonstrate that the presence of surface hydroxyl species by co-electrolysis of CO 2 with low concentrations of O 2 can dramatically enhance the activity of copper catalyzed CO 2 electroreduction. Our results indicate that co-electrolysis of CO 2 with an oxidant is a promising strategy to introduce catalytically active species in electrocatalysis. While the electrochemical conversion of CO 2 to highly reduced products is unique to copper, there are still gaps in understanding copper catalysts’ efficacy. Here, authors find that co-electrolysis of CO 2 with O 2 can enhance copper’s catalytic activities.

Electroreduction of carbon dioxide to hydrocarbons and oxygenates on copper involves reduction to a carbon monoxide adsorbate followed by further transformation to hydrocarbons and oxygenates. Simultaneous improvement of these processes over a single reactive site is challenging due to the linear scaling relationship of the binding strength of key intermediates. Herein, we report improved electroreduction of carbon dioxide by exploiting a one-pot tandem catalysis mechanism based on computational and electrochemical investigations. By constructing a well-defined copper-modified silver surface, adsorbed carbon monoxide generated on the silver sites is proposed to migrate to surface copper sites for the subsequent reduction to methane, which is consistent with insights gained from operando attenuated total reflectance surface enhanced infrared absorption spectroscopic investigations. Our results provide a promising approach for designing carbon dioxide electroreduction catalysts to enable one-pot reduction of products beyond carbon monoxide and formate. Carbon dioxide can be electrocatalytically reduced to valuable fuels and chemicals, but is hindered by poor catalytic efficiency and selectivity. Here the authors report improved electrocatalytic conversion of carbon dioxide into methane using a tandem catalysis strategy.

Despite the growing importance of fluorinated organic compounds in drug development, there are no direct protocols for the fluorination of aliphatic C-H bonds using conveniently handled fluoride salts. We have discovered that a manganese porphyrin complex catalyzes alkyl fluorination by fluoride ion under mild conditions in conjunction with stoichiometric oxidation by iodosylbenzene. Simple alkanes, terpenoids, and even steroids were selectively fluorinated at otherwise inaccessible sites in 50 to 60% yield. Decalin was fluorinated predominantly at the C2 and C3 methylene positions. Bornyl acetate was converted to exo-5-fluoro-bornyl acetate, and 5α-androstan-17-one was fluorinated selectively in the A ring. Mechanistic analysis suggests that the regioselectivity for C-H bond cleavage is directed by an oxomanganese(V) catalytic intermediate followed by F delivery via an unusual manganese(IV) fluoride that has been isolated and structurally characterized.

Organic molecules that contain alkyl-difluoromethyl moieties have received increased attention in medicinal chemistry, but their synthesis in a modular and late-stage fashion remains challenging. We report herein an efficient copper-catalyzed radical relay approach for the carbo-difluoromethylation of alkenes. This approach simultaneously introduces CF 2 H groups along with complex alkyl or aryl groups into alkenes with regioselectivity opposite to traditional CF 2 H radical addition. We demonstrate a broad substrate scope and a wide functional group compatibility. This scalable protocol is applied to the late-stage functionalization of complex molecules and the synthesis of CF 2 H analogues of bioactive molecules. Mechanistic studies and density functional theory calculations suggest a unique ligand effect on the reactivity of the Cu-CF 2 H species. Compounds that contain alkyl-difluoromethyl moieties are of interest for medicinal chemistry, but their synthesis is challenging. Here, the authors report a copper-catalyzed radical relay approach for the carbodifluoromethylation of alkenes that simultaneously introduces CF 2 H groups and complex alkyl or aryl groups into alkenes.

The oxidative dehydrogenation of propane, primarily sourced from shale gas, holds promise in meeting the surging global demand for propylene. However, this process necessitates high operating temperatures, which amplifies safety concerns in its application due to the use of mixed propane and oxygen. Moreover, these elevated temperatures may heighten the risk of overoxidation, leading to carbon dioxide formation. Here we introduce a microchannel reaction system designed for the oxidative dehydrogenation of propane within an aqueous environment, enabling highly selective and active propylene production at room temperature and ambient pressure with mitigated safety risks. A propylene selectivity of over 92% and production rate of 19.57 mmol m Cu −2 h −1 are simultaneously achieved. This exceptional performance stems from the in situ creation of a highly active, oxygen-containing Cu catalytic surface for propane activation, and the enhanced propane transfer via an enlarged gas-liquid interfacial area and a reduced diffusion path by establishing a gas-liquid Taylor flow using a custom-made T-junction microdevice. This microchannel reaction system offers an appealing approach to accelerate gas-liquid-solid reactions limited by the solubility of gaseous reactant. The activation of propane at mild conditions is challenging. Now a microfluidic reaction system with a Cu microtube serving as both the catalyst and the microchannel reactor can selectively convert propane to propylene at room temperature and ambient pressure.

Electrochemical reduction of CO2 (CO2ER) into fuels is a crucial strategy for mitigating climate change and meeting sustainable energy demands. Among catalytic materials, copper stands out due to its ability to convert CO2 into a diverse range of hydrocarbons and oxygenates with significant current density. Quantum mechanical studies have greatly advanced the understanding of CO2ER on copper surfaces; however, most have focused on thermodynamics and/or kinetics to elucidate reaction mechanisms or explain experimental trends, leaving orbital‐level insights largely unexplored. In this study, density functional theory calculations combined with intrinsic bond orbital analysis to track orbital evolution across 13 protonation steps involved in CO2ER to methane are employed. Based on these results, an arrow‐pushing diagram is constructed to illustrate the electron flow for each step. This methodology allows to identify the key orbital used by each CO2ER intermediate to accommodate the transferred proton. Furthermore, this approach also reveals that the copper electrode actively participates in six protonation steps by exchanging pairs of electrons with CO2ER intermediates that are either selectivity‐determining or rate‐determining steps. These insights deepen the understanding of CO2ER mechanisms and provide a foundation for developing strategies to enhance its efficiency and selectivity. Electrochemical CO2 reduction (CO2ER) on copper produces diverse fuels, yet orbital‐level insights remain limited. Using density functional theory and intrinsic bond orbital analysis, electron flow in 13 steps toward methane is tracked. The approach reveals how intermediates accept protons and how copper actively participates in key steps, offering a new framework to improve CO2ER efficiency.

The rotation of a C = C bond in an alkene can be efficiently accelerated by creating the high-strain ground state and stabilizing the transition state of the process. Herein, the synthesis, structures, and properties of several highly twisted alkenes are comprehensively explored. A facile and practical synthetic approach to target molecules is developed. The twist angles and lengths of the central C = C bonds in these molecules are 36–58° and 1.40–1.43 Å, respectively, and confirmed by X-ray crystallography and DFT calculations. A quasi-planar molecular half with the π-extended substituents delivers a shallow rotational barrier (down to 2.35 kcal/mol), indicating that the rotation of the C = C bond is as facile as that of the aryl-aryl bond in 2-flourobiphenyl. Other versatile and unique properties of the studied compounds include a broad photoabsorption range (from 250 up to 1100 nm), a reduced HOMO-LUMO gap (1.26–1.68 eV), and a small singlet-triplet energy gap (3.65–5.68 kcal/mol). The rotation of a carbon double bond in an alkene can be efficiently accelerated by creating the high strain ground state and stabilizing the transition state of the process. Here, the authors report the synthesis, structures, and properties of several highly twisted alkenes.

Electrochemical reduction of CO 2 (CO 2 ER) into fuels is a crucial strategy for mitigating climate change and meeting sustainable energy demands. Among catalytic materials, copper stands out due to its ability to convert CO 2 into a diverse range of hydrocarbons and oxygenates with significant current density. Quantum mechanical studies have greatly advanced the understanding of CO 2 ER on copper surfaces; however, most have focused on thermodynamics and/or kinetics to elucidate reaction mechanisms or explain experimental trends, leaving orbital‐level insights largely unexplored. In this study, density functional theory calculations combined with intrinsic bond orbital analysis to track orbital evolution across 13 protonation steps involved in CO 2 ER to methane are employed. Based on these results, an arrow‐pushing diagram is constructed to illustrate the electron flow for each step. This methodology allows to identify the key orbital used by each CO 2 ER intermediate to accommodate the transferred proton. Furthermore, this approach also reveals that the copper electrode actively participates in six protonation steps by exchanging pairs of electrons with CO 2 ER intermediates that are either selectivity‐determining or rate‐determining steps. These insights deepen the understanding of CO 2 ER mechanisms and provide a foundation for developing strategies to enhance its efficiency and selectivity.

Light alkane activation under mild conditions remains a substantial challenge. Here we report an aqueous reaction system capable of selectively converting light alkanes into corresponding olefins and oxygenates at room temperature and ambient pressure using Cu powder as the catalyst and O 2 as the oxidant. In ethane activation, we achieved a combined production of ethylene and acetic acid at a rate of 2.27 mmol g Cu −1  h −1 , with a combined selectivity up to 97%. Propane is converted to propylene with a selectivity up to 94% and a production rate up to 1.83 mmol g Cu −1  h −1 , while methane is converted mainly to carbon dioxide, methanol and acetic acid. On the basis of catalytic experiments, isotopic labelling experiments, spectroscopic insights and density functional theory calculations, we put forward mechanistic understandings in which the C–H bond is activated by the surface oxide species generated during the oxidation process, forming alkyl groups as key reaction intermediates. The activation of light alkanes under mild conditions is a challenging task. Now the conversion of alkanes into the corresponding olefins and oxygenates is achieved in solution using Cu powder at ambient temperature and pressure.