Electrochemical oxygen reduction at soft interfaces catalyzed by the transfer of hydrated lithium cations

Abstract

Initial oxygen concentration (ref. [2-4]) DMFc D 7.26 × 10 −6 cm•s −1 Diffusion coefficient of DMFc and DMFc + (ref. [5]) 2 O D 2.76 × 10 −5 cm•s −1 Diffusion coefficient of O2 (ref. [2]) ' OH w o o φ − ∆ ; however, to make the simulated CVs symmetric, and for the sake of convenience, −0.696 V was employed. 2 Component 1 (comp1) 2.1 Definitions 2.1.1 Variables Variables 3 Selection Geometric entity level Boundary Selection Boundary 2 Name Expression Description intcpl_source_Ibar pi*(rd^2)*F*(chds.ndflux_Maq-chds.ndflux_OHaq + chds.ndflux_Fcplusaq) 2.1.2 Component Couplings Integration 1 Coupling type Integration Operator name intop1 Source selection Geometric entity level Boundary Selection Boundary 2 2.2 Geometry 1 Geometry 1 Units Length unit m Angular unit deg Geometry statistics Property Value Space dimension 1 Number of domains 2 Number of boundaries 3 2.2.1 Interval 1 (i1) Selections of resulting entities Name Value Number of intervals One Left endpoint-0.01 Right endpoint 0 2.2.2 Interval 2 (i2) Selections of resulting entities Name Value Number of intervals One Left endpoint 0 Right endpoint 0.01 2.3 Transport of Diluted Species (chds) Transport of Diluted Species Selection Geometric entity level Domain Selection Domain 1 Equations Settings Description Value Concentration Linear Compute boundary fluxes On Apply smoothing to boundary fluxes On Value type when using splitting of complex variables Real Migration in electric field 0 2.5.1 Size (size) Settings Name Value Maximum element size 5e-6 Minimum element size 6.0E-6 Curvature factor 0.3 Maximum element growth rate 1.3 Custom element size Custom 2.5.2 Edge 1 (edg1) Selection Geometric entity level Remaining

Gold Nanofilm Redox Catalysis for Oxygen Reduction at Soft Interfaces

“…Crucially, the observation of this wave at an applied D w o f significantly below that required for IT of hydrated Li + (a key step in the biphasic reduction of organic solubilised O 2 [17]) is clear evidence that, under the experimental conditions described herein, aqueous solubilised O 2 is indeed being reduced (discussed more below). The reaction took place much faster with the AuNP nanofilm present (tens of minutes) than is the case for the Li + IT induced mechanism (equations (3) and (4)), which occurs on the time-scale of hours.…”

“…The IT step can be catalysed by the presence of various aniline derivatives [9,30] and free-base-or metalloporphyrins [44,45], porphines [42] or phthalocyanines [31] in the organic phase and the desired reduction product (H 2 O versus H 2 O 2 ) can be favoured by interfacial assemblies of cobalt porphyrins [12,32,33] or choice of electron donor [10]. Recently, biphasic O 2 reduction has been achieved under neutral and alkaline conditions [17]. Therein, the ET reduction of organic solubilised O 2 was facilitated by IT of hydrated metal cations (M + ) across the soft interface (see equations (3) and (4)).…”

“…However, to initiate such an IT required a substantial positive polarisation of the soft interface (D w o f% +500 mV) [17].…”

“…A burgeoning area of research is concerned with the biphasic electrocatalysis of redox reactions of interest for energy research, including the oxygen (O 2 ) reduction reaction (ORR) [9][10][11][12][13][14][15][16][17][18][19] and the hydrogen (H 2 ) evolution reaction (HER) [20][21][22][23][24][25][26][27][28], using soft interfaces functionalized with molecular species, metallic NPs or inorganic non-precious metal-based materials. The use of adsorbed solid particulate electrocatalysts at electrochemically polarisable soft interfaces has recently been reviewed by Dryfe and co-workers [29].…”

“…Whereas several reports have highlighted the catalysis of biphasic reactions by (i) facilitating the transfer of protons [12,30,31], or other ions [17], across the soft interface and (ii) the use of interfacial species, either molecular [12,32,33] or solid particulates [22,26], to coordinate reactants to enable electrocatalysis, far less common is (iii) the use of NPs as bipolar electrodes to facilitate catalysis via direct interfacial electron transfer (IET) between a lipophilic electron donor and a hydrophilic electron acceptor or vice versa [8]. Such a process is termed interfacial redox catalysis.…”