Electrochemical reduction of carbon dioxide on copper in methanol with various potassium supporting electrolytes at low temperature

The electrochemical reduction of CO₂ at a Cu electrode was investigated in a methanol-based electrolyte using such potassium supporting salts as CH₃COOK, KBr, KI and KSCN at extremely low temperature (−30 °C). The main products obtained from CO₂ by the electrochemical reduction were methane, ethylene, ethane, carbon monoxide and formic acid. The maximum Faradaic efficiency of ethylene was 19.9% in KI/methanol-based catholyte at −3.0 V vs. Ag/AgCl saturated KCl. The best methane formation (27.0%) was obtained in CH₃COOK/methanol electrolyte at −3.0 V. In the system containing a potassium halide, the efficiency of hydrogen formation, being a competitive reaction against CO₂ reduction, was suppressed to less than 8.1%. The product selectivity of the electrochemical reduction of CO₂ in methanol was greatly affected by the anionic species. This research can contribute to the large-scale manufacturing of useful organic products from readily available and cheap raw materials: CO₂-saturated methanol from industrial absorbers (the Rectisol process). Received: 11 November 1998 / Accepted: 1 February 1999     

Densely Packed,Ultra Small SnO Nanoparticles for Enhanced Activity and Selectivity in Electrochemical CO2 Reduction

Controlling the selectivity in electrochemical CO₂ reduction is an unsolved challenge. While tin (Sn) has emerged as a promising non‐precious catalyst for CO₂ electroreduction, most Sn‐based catalysts produce formate as the major product, which is less desirable than CO in terms of separation and further use. Tin monoxide (SnO) nanoparticles supported on carbon black were synthesized and assembled and their application in CO₂ reduction was studied. Remarkably high selectivity and partial current densities for CO formation were obtained using these SnO nanoparticles compared to other Sn catalysts. The high activity is attributed to the ultra‐small size of the nanoparticles (2.6 nm), while the high selectivity is attributed to a local pH effect arising from the dense packing of nanoparticles in the conductive carbon black matrix.     

Densely Packed,Ultra Small SnO Nanoparticles for Enhanced Activity and Selectivity in Electrochemical CO2 Reduction

Controlling the selectivity in electrochemical CO₂ reduction is an unsolved challenge. While tin (Sn) has emerged as a promising non‐precious catalyst for CO₂ electroreduction, most Sn‐based catalysts produce formate as the major product, which is less desirable than CO in terms of separation and further use. Tin monoxide (SnO) nanoparticles supported on carbon black were synthesized and assembled and their application in CO₂ reduction was studied. Remarkably high selectivity and partial current densities for CO formation were obtained using these SnO nanoparticles compared to other Sn catalysts. The high activity is attributed to the ultra‐small size of the nanoparticles (2.6 nm), while the high selectivity is attributed to a local pH effect arising from the dense packing of nanoparticles in the conductive carbon black matrix.     

Controlling the Product Platform of Carbon Dioxide Reduction: Adaptive Catalytic Hydrosilylation of CO2 Using a Molecular Cobalt(II) Triazine Complex

The catalytic reduction of carbon dioxide (CO₂) is considered a major pillar of future sustainable energy systems and chemical industries based on renewable energy and raw materials. Typically, catalysts and catalytic systems are transforming CO₂ preferentially or even exclusively to one of the possible reduction levels and are then optimized for this specific product. Here, we report a cobalt‐based catalytic system that enables the adaptive and highly selective transformation of carbon dioxide individually to either the formic acid, the formaldehyde, or the methanol level, demonstrating the possibility of molecular control over the desired product platform.     

Aqueous Electrochemical Reduction of Carbon Dioxide and Carbon Monoxide into Methanol with Cobalt Phthalocyanine

Conversion of CO₂ into valuable molecules is a field of intensive investigation with the aim of developing scalable technologies for making fuels using renewable energy sources. While electrochemical reduction into CO and formate are approaching industrial maturity, a current challenge is obtaining more reduced products like methanol. However, literature on the matter is scarce, and even more for the use of molecular catalysts. Here, we demonstrate that cobalt phthalocyanine, a well‐known catalyst for the electrochemical conversion of CO₂ to CO, can also catalyze the reaction from CO₂ or CO to methanol in aqueous electrolytes at ambient conditions of temperature and pressure. The studies identify formaldehyde as a key intermediate and an unexpected pH effect on selectivity. This paves the way for establishing a sequential process where CO₂ is first converted to CO which is subsequently used as a reactant to produce methanol. Under ideal conditions, the reaction shows a global Faradaic efficiency of 19.5 % and chemical selectivity of 7.5 %.     

How to Control the Chemoselectivity of the Catalytic Formation of Chiral γ-Lactams or 2,3-Disubstituted Pyrroles by the Choice of Solvent

Summary. The reaction of the unsaturated imine methyl(3-phenylallylidene)amine with ethylene and carbon monoxide in the presence of catalytical amounts of Ru₃(CO)₁₂ leads to the formation of two heterocyclic products. One of the products is a chiral γ-lactam, the other one a 2,3-disubstituted pyrrole derivative, in which only the carbon atom from carbon monoxide is incorporated. The selectivity in the formation of the products may be controlled by the choice of solvent. In general, in nonpolar solvents the formation of the lactam is preferred whereas the use of more polar solvents enhances the yield of the pyrrole. For most of the solvents used there is a linear dependence of the product ratio on the relative permittivity of the corresponding solvent. Typically, polar aprotic solvents do not follow this rule.     

Variation of the activity of СuO·ZnO·K<Subscript>2</Subscript>O/SiO<Subscript>2</Subscript> catalysts during generation in dehydrogenation of methanol to formaldehyde

The development of the catalytic properties of supported model catalysts СuO·ZnO·K₂O/SiO₂ with different component ratios in methanol dehydrogenation was studied. In the temperature interval 400–500°С, the formation of the target product, formaldehyde, is accompanied by the formation of surface polymeric hydrocarbons, which undergo gradual condensation to coke with the evolution of hydrogen and carbon dioxide. By properly combining the concentrations of the supported components and the sequence of the deposition of zinc, copper, and potassium oxides, it is possible to reduce the time in which the steady-state catalyst operation mode is reached and to improve the catalyst selectivity with respect to formaldehyde formation.     

A New Nanocomposite Based on Pt-rGO Embedded Polymelamine Formaldehyde Nanocomposite for Reduction of Carbon Dioxide

Here, polymelamine formaldehyde was decorated on the surface of reduced graphene oxide whose surface was then electrodeposited with a sub-monolayer of platinum nanoparticles. The nanocomposite thus prepared was characterized using several spectroscopic methods. Using the nanocomposite as a potential electrocatalyst for carbon dioxide reduction, the products were detected by Raman spectroscopy, gas chromatography, ¹³C-NMR spectroscopy, and gas chromatography-mass spectrometry. The analytical results identified methanol as the main product of CO₂ reduction. Moreover, analysis of the liquid products confirmed methanol as the predominant product with a current density of 0.4 mA/cm and a Faradaic efficiency of 93 %.     

Effect of sodium cation on the electrochemical reduction of CO<Subscript>2</Subscript> at a copper electrode in methanol

The electrochemical reduction of CO₂ with a Cu electrode in methanol was investigated with sodium hydroxide supporting salt. A divided H-type cell was employed; the supporting electrolytes were 80 mmol dm⁻³ sodium hydroxide in methanol (catholyte) and 300 mmol dm⁻³ potassium hydroxide in methanol (anolyte). The main products from CO₂ were methane, ethylene, carbon monoxide, and formic acid. The maximum current efficiency for hydrocarbons (methane and ethylene) was 80.6%, at −4.0 V vs Ag/AgCl, saturated KCl. The ratio of current efficiency for methane/ethylene, r _f(CH₄)/r _f(C₂H₄), was similar to those obtained in LiOH/methanol-based electrolyte and larger relative to those in methanol using KOH, RbOH, and CsOH supporting salts. In NaOH/methanol-based electrolyte, the efficiency of hydrogen formation, a competing reaction of CO₂ reduction, was suppressed to below 4%. The electrochemical CO₂ reduction to methane may be able to proceed efficiently in a hydrophilic environment near the electrode surface provided by sodium cation.     

Chimie organometallique : XII. Homologation du methanol par des catalyseurs homogenes derives du rhodium

Reaction of methanol, carbon monoxide and hydrogen in the presence of a rhodium catalyst gives the homologization product, ethanol, with a selectivity of up to 50%, for a H₂/CO ratio equal to 40. A mechanism for the reaction is suggested.     

铜锌催化剂上吸附动力学参数的非线性动态分析

本文得到了适应于一氧化碳加氢加压体系非线性动态分析不同吸附物种动力学参数的模型，并优化出工业铜锌催化剂上合成甲醇反应中可逆吸附氢和可逆吸附一氧化碳的吸附速率常数及吸附平衡常数。结果表明：铜锌催化剂上吸附可逆氢比吸附一氧化碳快７倍左右。由于铜锌催化剂上甲醇的生成是可逆吸附氢与可逆吸附一氧化碳共同作用的结果，且铜锌催化剂 可逆吸一氧化碳的表面浓度随气相一氧化碳分压的增加而增加，因而加压将有利于合成甲醇     

Using the Secondary PH/BH Functional Groups of an Active Geminal Frustrated Lewis Pair for Carbon Monoxide Reduction and Reactions with Nitriles and Isonitriles

Reaction of the secondary alkynyl(Mes*)PH phosphane 2 with (Fmes)BH₂?SMe₂ gives the geminal PH/BH frustrated Lewis pair (FLP) 3 . The PH and the BH functions are jointly used in the reduction of carbon monoxide under mild reaction conditions to give the [P]‐CH₂‐O‐[B] product. A subsequent cycloaddition sequence results in the liberation of formaldehyde. The FLP 3 reacts with benzonitrile to give a P‐benzamidine, and it couples two isonitriles at the FLP framework.     

Lateral Adsorbate Interactions Inhibit HCOO− while Promoting CO Selectivity for CO2 Electrocatalysis on Silver

Ag is a promising catalyst for the production of carbon monoxide (CO) via the electrochemical reduction of carbon dioxide (CO₂ER). Herein, we study the role of the formate (HCOO^?) intermediate *OCHO, aiming to resolve the discrepancy between the theoretical understanding and experimental performance of Ag. We show that the first coupled proton‐electron transfer (CPET) step in the CO pathway competes with the Volmer step for formation of *H, whereas this Volmer step is a prerequisite for the formation of *OCHO. We show that *OCHO should form readily on the Ag surface owing to solvation and favorable binding strength. In situ surface‐enhanced Raman spectroscopy (SERS) experiments give preliminary evidence of the presence of O‐bound bidentate species on polycrystalline Ag during CO₂ER which we attribute to *OCHO. Lateral adsorbate interactions in the presence of *OCHO have a significant influence on the surface coverage of *H, resulting in the inhibition of HCOO^? and H₂ production and a higher selectivity towards CO.     

Electrochemical and FTIR spectroscopic study of CO2 reduction at a nanostructured Cu/reduced graphene oxide thin film

Here we report a facile approach to synthesize a novel nanostructured thin film comprising Cu nanoparticles (NPs) and reduced graphene oxide (rGO) on a glassy carbon electrode (GCE) via the direct electrochemical reduction of a mixture of cupper and graphene oxide (GO) precursors. The effect of the applied potential on the electrochemical reduction of CO₂ was investigated using linear sweep voltammetric (LSV) and chronoamperometric (CA) techniques. Carbon monoxide and formate were found as the main products based on our GC and HPLC analysis. The electrochemical reduction of CO₂ at the Cu/rGO thin film was further studied using in situ ATR-FTIR spectroscopy to identify the liquid product formed at different applied cathodic potentials. Our experimental measurements have shown that the nanostructured Cu/rGO thin film exhibits an excellent stability and superb catalytic activity for the electrochemical reduction of CO₂ in an aqueous solution with a high current efficiency of 69.4% at − 0.6 V vs. RHE, promising for the efficient electrochemical conversion of CO₂ to valuable products.     

Experimental study of photocatalytic oxidation of formaldehyde and its by-products

Formaldehyde is one of the most harmful pollutants that endanger occupants' health and the way of its effective removal has become a focus in the field of air quality. This paper studies the static photocatalytic removal of formaldehyde experimentally and finds out that carbon monoxide, which is more harmful to occupants' health than the formaldehyde itself, is one of the by-products in the process of photocatalytic oxidation of formaldehyde. The increase of carbon monoxide concentration should be taken into consideration in the photocatalytic application. The photocatalyst surface at room temperature can weakly adsorb CO and CO₂, which can deactivate the photocatalysts.     

Wet Conversion of Methane and Carbon Dioxide in a DBD Reactor

The influence of water on the plasma assisted conversion of methane and carbon dioxide in a dielectric barrier discharge (DBD) plug flow reactor was studied. The plasma at atmospheric pressure was ignited by a power supply at a frequency of 13.56?MHz. Product formation was studied at a power range between 35 and 70?W. The concentrations of the three gases were altered and diluted with helium to 3?%. FTIR spectroscopy and mass spectroscopy were applied to analyze the inlet and the product streams. The main product of this process are hydrogen, carbon monoxide and ethane. Ethene, ethine, methanol and formaldehyde are generated beside the main products in this DBD in lower concentrations. The conversion of methane, the ratio of the synthesis gas components (n(H₂):n(CO)), and the yield of oxygenated hydrocarbons and hydrogen increases by adding water. The total consumed energy reaches lower values for small amounts of water. Additional water does not influence the generated amount of C2 hydrocarbons and of CO, but decreases the carbon dioxide conversion.     

Decarbonylation of N-carbazolylacetyl chloride in the friedel-crafts acylation reaction

Reaction products of N-carbazolylacetyl chloride under Friedel-Crafts reaction conditions include carbon monoxide, the reaction product from carbazole and formaldehyde (CF condensate), and carbazole. It is postulated that decarbonylation of N-carbazolylacetyl chloride involves intermediate formation of a N-carbazolylmethyl cation.     

纳米晶枝CuAu合金催化剂对二氧化碳电催化还原性能的研究

利用可再生清洁能源将CO2转化为CO和其他小分子是合成含碳燃料的可观方法之一.间歇性可再生能源存储的重要策略之一是将二氧化碳进行电化学还原.选择具有高活性和稳定性的电催化剂对于电化学还原CO2至关重要.在这项研究中,我们使用简单的电沉积方法合成了具有纳米晶枝状结构的CuAu合金电极.各项表征显示原子比约为1∶1的CuA...     

Methane Photooxidation with Nearly 100 % Selectivity Towards Oxygenates: Proton Rebound Ensures the Regeneration of Methanol

Restrained by uncontrollable dehydrogenation process, the target products of methane direct conversion would suffer from an inevitable overoxidation, which is deemed as one of the most challenging issues in catalysis. Herein, based on the concept of a hydrogen bonding trap, we proposed a novel concept to modulate the methane conversion pathway to hinder the overoxidation of target products. Taking boron nitride as a proof-of-concept model, for the first time it is found that the designed N−H bonds can work as a hydrogen bonding trap to attract electrons. Benefitting from this property, the N−H bonds on the BN surface rather than C−H bonds in formaldehyde prefer to cleave, greatly suppressing the continuous dehydrogenation process. More importantly, formaldehyde will combine with the released protons, which leads to a proton rebound process to regenerate methanol. As a result, BN shows a high methane conversion rate (8.5 %) and nearly 100 % product selectivity to oxygenates under atmospheric pressure.     

Production of acetylene by a microwave catalytic reaction of water and carbon

The feasibility of producing hydrocarbons in a microwave induced catalytic reaction of carbon and water was successfully demonstrated. The major reaction products are acetylene, methane, ethylene and ethane. Other significant products include propylene, propyne, cyclopropane, carbon dioxide and carbon monoxide. Relative product yields and their distribution depend on a number of experimental variables, such as irradiation time, incident microwave power, water/carbon ratio and the characteristics of the microwave pulse train. At short irradiation times and low incident power only C₁ — C₂ products were observed, their rates of formation being an exponential function of the incident microwave power. High incident power led to the formation of C₃ to C₆ hydrocarbons at the expense of acetylene. Initial addition of methane and carbon dioxide to the reaction mixture increased the yield of acetylene, whereas addition of methanol to water resulted in a sharp increase in the amounts of both methane and acetylene. Mechanisms are considered to account for these observations.