Jia-Xing Lu

Electrochemical activation of CO2 in ionic liquid (BMIMBF4): synthesis of organic carbonates under mild conditions

A new electrochemical procedure for electrosynthesis of organic carbonates from CO2 and alcohols has been established in CO2-saturated room temperature ionic liquid BMIMBF4 solution, followed by addition of an alkylating agent. The synthesis was carried out under mild (PCO2 =1.0 atm, T = 55 °C) and safe conditions. The use of volatile and toxic solvents and catalysts as well as of any additional supporting electrolytes has been avoided. The influence of temperature, cathode material, working potential, alcohol concentration and the charge passed on the reaction using methanol (1a) as the model compound was examined. The ionic liquid used for the reaction was recyclable. The obtained results showed that the primary and secondary alcohols were converted in good yields, whereas tertiary alcohol and phenol were unreactive.

Morphology-controlled CuO nanoparticles for electroreduction of CO2 to ethanol

CuO nanoparticles with five morphologies were synthesized in large quantities using a simple method. They were in situ reduced to metallic Cu for the electroreduction of CO2. Alcohols with excellent selectivity for ethanol were obtained. The specific morphology was demonstrated to be more electrocatalytically active than others by multiple methods.

Organically doped palladium: a highly efficient catalyst for electroreduction of CO2 to methanol

A [PYD]@Pd composite was prepared by the entrapment of a pyridine derivative within metallic palladium. Metallic Pd acts as a heterogeneous support and a pyridine ring served as an active site for electroreduction of CO2, and no additional catalyst was needed in the electrolyte. 35% Faradaic efficiency of methanol was obtained at only −0.6 V vs. SCE. Moreover, [PYD]@Pd has remarkable stability and reusability.

Electrocatalytic reduction of carbon dioxide by cobalt-phthalocyanine-incorporated polypyrrole

In the quest for catalysts for the electrocatalytic reduction of CO 2 , a cobalt phthalocyanine/polypyrrole (CoPc/PPy) composite electrode has been developed. The electrode is prepared by drop casting CoPc onto the PPy film from the CoPc/tetrahydrofuran solution (1 mg/mL). The onset potential for CO 2 reduction occurred at potentials 160 mV more positive than observed with a simple PPy electrode. Furthermore, in the potentiostatic electrolysis, the catalytic current for CO 2 reduction at CoPc/PPy was very stable, with a higher current density and current efficiency when compared to the PPy electrode.

Selective electrochemical reduction of CO2 to different alcohol products by an organically doped alloy catalyst

A highly stable and recyclable catalyst, [PYD]@Cu–Pt, was demonstrated to have dual activity for electrochemical reduction of CO2 in aqueous solution. Different alcohol products could be obtained by simply switching the working potential. Through contrast experiments, a feasible reaction pathway was proposed to explain this dual activity.

Entrapment of a pyridine derivative within a copper–palladium alloy: a bifunctional catalyst for electrochemical reduction of CO2 to alcohols with excellent selectivity and reusability

A novel bifunctional catalyst, [PYD]@Cu–Pd composite, was synthesized for the first time and used as a cathode for electrochemical reduction of CO2. Methanol with 26% and ethanol with 12% Faradaic efficiency were obtained at the same [PYD]@Cu–Pd cathode using different potentials. Under both conditions, the [PYD]@Cu–Pd cathode shows remarkable stability and reusability.

Remarkable Sensitivity of the Electrochemical Reduction of Benzophenone to Proton Availability in Ionic Liquids

The reduction of benzophenone was investigated in five different ionic liquids by using transient cyclic voltammetry, near steady-state voltammetry, and numerical simulation. Two reversible, well-resolved one-electron-reduction processes were observed in dry (≤20 ppm water, ca. 1 mM)) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Bmpyrd][NTf(2)]) and 1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide ([Bmpipd][NTf(2)]), which did not contain any readily available proton source. Upon addition of water, the second process became chemically irreversible and shifted to a more positive potential by approximately 600 mV; moreover, the two reduction processes merged into a single two-electron proton-coupled process when about 0.6 M H(2)O was present. This large dependence of potential on water content, which was not observed in molecular solvents (electrolyte), was explained by a reaction mechanism that incorporated protonation and hydrogen-bonding interactions of the benzophenone dianion with as many as seven water molecules. In the three imidazolium-based ionic liquids used herein, the first benzophenone-reduction process was again reversible, whilst the second reduction process became chemically irreversible owing to the availability of the C2-H imidazolium protons in these ionic liquids. The reversible potentials for benzophenone reduction were remarkably independent of the identity of the ionic liquids, thereby implying either weak interactions with the ionic liquids or relatively insignificant differences in the levels of ion-pairing. Thus, the magnitude of the separation of the potentials of the reversible first and irreversible second reduction processes mainly reflected the proton availability from either the ionic liquid itself or from adventitious water. Consequently, voltammetric reduction of benzophenone provides a sensitive tool for the determination of proton availability in ionic liquids.

Electrocatalytic Carboxylation of Arylic Bromides at Silver Cathode in the Presence of Carbon Dioxide

Abstract A simple and efficient electrocatalytic carboxylation of arylic bromides has been developed using silver as cathode and magnesium as anode in N,N-dimethylformamide (DMF) under mild conditions. The influences of some key factors (such as the nature of cathode material, current density, and temperature) on this reaction were investigated. The investigations were extended to other arylic bromides under the optimized conditions, and the corresponding carboxylic acids were obtained in moderate to good yields (30–78%). The electrochemical behavior was studied at different electrodes (Ag, Cu, Ni, and Ti) by cyclic voltammetry, which showed significant electrocatalytic effect of the silver electrode toward the reductive carboxylation of arylic bromides.

A unique proton coupled electron transfer pathway for electrochemical reduction of acetophenone in the ionic liquid [BMIM][BF4] under a carbon dioxide atmosphere

The mechanism of electrochemical reduction of acetophenone in 1-butyl-3-methylimidazolium tetrafluroborate ([BMIM][BF4]) under nitrogen (N2) and carbon dioxide (CO2) atmospheres have been investigated using transient voltammetry, steady-state voltammetry, bulk electrolysis and numerical simulation. Under a N2 atmosphere, acetophenone undergoes a one-electron reduction to the radical anion followed by rapid dimerization reactions with an apparent rate constant of 1.0 × 106 M−1s−1. In contrast, under a CO2 atmosphere, the electrochemical reduction of acetophenone is an overall two-electron transfer chemically irreversible process with the final electrolysis product being 1-phenylethanol, instead of the anticipated 2-hydroxy-2-phenylpropionic acid resulting from an electrocarboxylation reaction. A proton coupled electron transfer pathway leading to the formation of 1-phenylethanol requires the presence of a sufficiently strong proton donor which is not available in neat [BMIM][BF4]. However, the presence of CO2 enhances the C-2 hydrogen donating ability of [BMIM]+ due to strong complex formation between the deprotonated form of [BMIM]+, N-heterocyclic carbene, and CO2, resulting in a thermodynamically favorable proton coupled electron transfer pathway.

Electrosynthesis of cyclic carbonates from CO2 and epoxides on a reusable copper nanoparticle cathode

A highly stable and reusable Cu NP cathode was prepared by a simple method and used for the electrosynthesis of cyclic carbonates by electroreduction of CO2 in the presence of epoxides under mild conditions. No added metal catalyst is required and the yields vary from moderate to very good. Furthermore, the activity of the cathode was shown to depend on the size of the Cu NPs.