Oxygen Reduction at the Liquid–Liquid Interface: Bipolar Electrochemistry through Adsorbed Graphene Layers

Abstract

The reduction of oxygen and protons at the interface between two immiscible electrolyte solutions (ITIES) has received a great deal of interest over the last decade, with various materials being used to catalyse these reactions. Probing the mechanisms through which these reactions proceed when using interfacial catalysts is important from both from the perspective of fundamental understanding and for catalyst optimisation. Herein, we have used interfacial‐assembled graphene to probe the importance of simple electron conductivity towards the catalysis of the oxygen reduction reaction (ORR) at the ITIES, and a bipolar setup to probe the homogeneous/heterogeneous nature of the ORR proceeding through interfacial graphene. We found that interfacial graphene provides a catalytic effect towards the reduction of oxygen at the ITIES, proceeding via the heterogeneous mechanism when using a strong reducing agent.

Electrochemical Investigation of Adsorption of Single-Wall Carbon Nanotubes at a Liquid/Liquid Interface

“…Dibenzo‐18‐crown‐6 (98+%) was a product of Lancaster Synthesis. The bis(triphenylphosporanylidene) ammonium tetrakis(4‐chlorophenyl) borate (BTPPATPCl) used as the organic‐phase electrolyte was prepared as described previously . Ultrapure water (18.2 MΩ cm resistivity, Milli‐Q Direct 8, Merck Millipore, USA) was used for aqueous solutions preparation.…”

“…This was utilized to functionalize interfacial SWCNT and graphene layers with metal nanoparticles by reducing aqueous metal salts using an organic electron donor, and a conducting polymer poly(pyrrole), through oxidation of the pyrrole monomer dissolved in the organic phase by an aqueous oxidizing agent. Similarly, the electron‐transfer‐mediating properties of pristine liquid‐phase exfoliated graphene at the water/organic interface were found to result in a catalytic effect on the heterogeneous oxygen reduction reaction . Furthermore, the electrochemical doping of the interfacial SWCNTs was investigated by using in situ Raman spectroelectrochemistry …”

H2O2 Generation at a Carbon‐Paste Electrode with Decamethylferrocene in 2‐Nitrophenyloctyl Ether as a Binder: Catalytic Effect of MoS2 Particles

“…It is also important to emphasize that these color changes are not seen under anaerobic conditions, which indicates negligible formation of hydrogen in studied system. [15][16][17][18][19] The progress of reactionw as also followedb yU V/Vis spectroscopy ( Figure 2A)O ne can see ad ecrease in the band at l = 425 nm, whichi sc haracteristic of DMFc in organic solution, and the appearance of ab and at l = 779 nm, which is characteristicoft he presence of DMFc + . [7] When KI ands tarch werea dded to the aqueous phase taken from the experiments with acidic aqueous solution, the color changed to violet (Figure1C, flasks 1a nd 3) due to the oxidation of iodide to triiodide by newly formed H 2 O 2 and subsequent formation of av iolet complex of I 3 À with starch.…”

“…When NPOE is in contact with the acidic solution, the change in color is even more pronounced in the presence of MoS 2 particles (Figure A, B, flask 3), which demonstrates their catalytic activity in this reaction. It is also important to emphasize that these color changes are not seen under anaerobic conditions, which indicates negligible formation of hydrogen in studied system . The progress of reaction was also followed by UV/Vis spectroscopy (Figure A) One can see a decrease in the band at λ =425 nm, which is characteristic of DMFc in organic solution, and the appearance of a band at λ =779 nm, which is characteristic of the presence of DMFc + …”

Molecular Caging of Graphene with Cyclohexane: Transfer and Electrical Transport

“…Such organic–aqueous interfaces have been used for separating and extracting products of chemical reactions 15,16 and have the potential for in situ graphene functionalization 17,18 and electrochemistry. 19,20 …”