Copper-zeolite-modified electrodes: An intrazeolite ion transport mechanism

A new method for preparing mechanically stable dense 1 μm zeolite monograin layers on substrate electrodes allows detailed information on the electrochemical behaviour of Cu2+-zeolite-modified electrodes to be obtained. The conductivity of the Cu2+-Y-zeolite layers depends on the electrolyte cations and decreases in the order Cs+ & >; K+ & >; Na+ & >; Li+. Experiments on thick zeolite layers composed of stacked zeolite particles show that only the Cu2+ ions in the first layer take part in the electrode process. Significant differences between the cyclic voltammograms of Cu2+ at the unmodified glassy carbon electrodes and at the zeolite-modified electrodes are observed. Our experiments clearly demonstrate that the electrochemical processes at monograin Cu2+-Y-zeolite-modified electrodes are of intrazeolite ion transport type. Cu2+ ions in A zeolites are electrochemically ‘silent’ in the potential range from 0.5 to −0.8 V/SCE, in strong contrast with Cu2+-Y-zeolite but in agreement with the fact that A zeolites do not support high Cu2+ exchange.