Improvement of electrochemically mediated atom transfer radical polymerization: Use of aluminum as a sacrificial anode in water

The simplest electrolytic devices are undivided electrochemical cells without any separator between anodic and cathodic compartments. These simple yet efficient electrochemical cells often require the use of sacrificial metal counter electrodes, which, however, are incompatible with many electrocatalytic systems. In this article, we investigate the effect of the presence of an Al anode on an electrocatalytic reaction in water, namely electrochemically-mediated atom transfer radical polymerization (eATRP) catalyzed by common Cu complexes with amine ligands. It was found that the sacrificial anode could undermine the reactivity of the aqueous Cu catalysts in two ways: i) protonation of the amine ligand promoted by the release of acidic Al3+ ions; ii) spontaneous deposition of Cu0 on the Al metal surface. Both pathways led to decomposition of the original copper catalyst. To avoid undesired side reactions arising from the Al anode, simple strategies involving the use of appropriate amine ligands and pH buffers are described.