We describe a new strategy for enhancing the efficiency of electrocatalytic CO2 reduction with a homogeneous catalyst, using a room-temperature ionic liquid as both the solvent and electrolyte. The electrochemical behavior of fac-ReCl(2,2′-bipyridine)(CO)3 in neat 1-ethyl-3-methylimidazolium tetracyanoborate ([emim][TCB]) was compared with that in acetonitrile containing 0.1 M [Bu4N][PF6]. Two separate one-electron reductions occur in acetonitrile (−1.74 and −2.11 V vs Fc+/0), with a modest catalytic current appearing at the second reduction wave under CO2. However, in [emim][TCB], a two-electron reduction wave appears at −1.66 V, resulting in a ∼0.45 V lower overpotential for catalytic reduction of CO2 to CO. Furthermore, the apparent CO2 reduction rate constant, kapp, in [emim][TCB] exceeds that in acetonitrile by over one order of magnitude (kapp = 4000 vs 100 M–1 s–1) at 25 ± 3 °C. Supported by time-resolved infrared measurements, a mechanism is proposed in which an interaction between [emim]+ and the...

Electrocatalytic CO2 Reduction with a Homogeneous Catalyst in Ionic Liquid: High Catalytic Activity at Low Overpotential

We demonstrate that a microelectrode can be used as a diagnostic tool to optimize the properties of electrolytes for non-aqueous Li-air batteries, and to elucidate the influence of ion-conducting salts on O2 reduction reaction mechanisms. Oxygen reduction/evolution reactions on carbon microelectrode have been studied in dimethyl sulfoxide-based electrolytes containing Li+ and tetrabutylammonium((C4H9)4N+) ions. Analysis of chronoamperometric current-time transients of the oxygen reduction reactions (ORR) in the series of tetrabutylammmonium (TBA) electrolytes, TBAPF6, TBAClO4, TBACF3SO3, TBAN(CF3SO2)2 in DMSO revealed that the anion of the salt exerts little influence on oxygen transport. Whereas steady-state ORR currents(sigmoidal-shaped) were observed in TBA-based electrolytes, peak-shaped current-voltage profiles were seen in the electrolytes containing their Li salt counterparts. The latter response results from the combined effects of the electrostatic repulsion of the superoxide intermediate as it is reduced further to peroxide (O22−) at low potentials, and the formation of passivation films at the electrode. Raman spectroscopic data confirmed the formation of Li2O2 and Li2O on the microelectrode surface at different reduction potentials in Li salt solutions. Out of the four lithium electrolytes, namely LiPF6, LiClO4, LiCF3SO3, or LiN(CF3SO2)2 in DMSO, the LiCF3SO3/DMSO solution revealed the most favorable ORR kinetics and the least passivation of the electrode by ORR products. © 2014 The Electrochemical Society. [DOI: 10.1149/2.073403jes] All rights reserved.

http://jes.ecsdl.org/content/161/3/A381.full.pdf

Microelectrode Diagnostics of Lithium-Air Batteries

Dinuclear Coinage-Metal Complexes of Bis(NHC) Ligands: Structural Features and Dynamic Behavior of a Cu–Cu Complex

Estimation of diffusion coefficients by using a linear correlation between the diffusion coefficient and molecular weight

Modelling ac voltammetry with MECSim: facilitating simulation–experiment comparisons

Cyclic voltammetry data recorded at disk macro- (millimeter dimension) and microelectrodes (10 and 100 μm) at various scan rates are used to simultaneously determine the diffusion coefficient D of ferrocene (fc) and the electroactive surfaces A and/or radii r of the electrodes. A case study with three electrodes of different sizes in CH3CN- and propylene carbonate (PC)-based electrolytes shows the possibly large effect of incorrect D values. Diffusion coefficients of fc are determined for PC, CH3CN, CH2Cl2, DMF, and DMSO electrolytes and (except for PC) compared to those from pulse-gradient spin-echo nuclear magnetic resonance experiments in the presence of supporting electrolyte in the respective deuterated solvents. The dependence of D fc on solvent viscosity is shown to follow the Stokes–Einstein relation.

Consistent diffusion coefficients of ferrocene in some non-aqueous solvents: electrochemical simultaneous determination together with electrode sizes and comparison to pulse-gradient spin-echo NMR results

EChem++ – An object-oriented problem solving environment for electrochemistry. Part 7: Simulation of equilibrium electron transfer processes with implicit Dirichlet boundary conditions

Steffi Benthin

Papers

Consistent diffusion coefficients of ferrocene in some non-aqueous solvents: electrochemical simultaneous determination together with electrode sizes and comparison to pulse-gradient spin-echo NMR results

EChem++ – An object-oriented problem solving environment for electrochemistry. Part 7: Simulation of equilibrium electron transfer processes with implicit Dirichlet boundary conditions