Paired electrosynthesis: micro-flow cell processes with and without added electrolyte

The thin layer flow cell geometry with working and auxiliary electrodes directly facing each other, allows electrosynthetic processes to be conducted in flow-through mode. At sufficiently small cell height, the two diffusion layers of working and auxiliary electrode overlap or become 'coupled'. As a result electro-generated acids or bases are instantaneously neutralised, products from anode and cathode can interact, and, more importantly, bulk electrolysis is possible without intentionally added electrolyte. In this preliminary report, the operation of a micro-flow cell with coupled diffusion layers is demonstrated for the one electron oxidation of ferrocene and for the two electron-two proton reduction of tetraethyl ethylenetetracarboxylate dissolved in ethanol. In proof-of-principle bulk electrolysis experiments without intentionally added electrolyte, high yields of the product, tetraethyl ethanetetracarboxylate are obtained at a nickel working electrode. It is demonstrated that a sufficient concentration of electrolyte for bulk electrolysis is generated locally and in situ between working and auxiliary electrode. (C) 2002 Elsevier Science B.V. All rights reserved.