MICROHETEROGENEOUS DISPERSION ELECTROLYSIS WITH NANOSCALE ELECTRODE-MODIFIED ZEOLITES

This study demonstrates the utility of supported nanoscale Pt or RuO2 particles as ensembles of ultramicroelectrodes for controlled potentia l electrolyses, including implications for their use in practical elec trosyntheses. Microheterogeneous dispersions of nanoelectrode-modified aluminosilicate zeolites (M-Z) increase the effective electrode area of conventional large surface electrodes in electrolytes of customary ionic strength (mu greater than or equal to 0.1 M). For [Fe(CN)(6)](3- ) solutions (in pH 6.86 phosphate buffer), the time for total reductio n of the iron complex using a dilute 2.5 mg/ml suspension density of 1 wt.% Pt-NaY was 67% less than that for the same solution with no elec trode-modified zeolite added. The use of Pt-NaY dispersed in solutions of low electrolyte content (650 mu M) exploits the nanoelectrode natu re of the Pt particles and enables effective electron transfer to be c onducted at applied potentials similar to those applied in high ionic strength electrolyte. In the absence of dispersed nanoelectrodes, no e lectrolysis can be sustained under these conditions of high resistance . Divorcing the electrocatalyst from the reactor electrodes allows ine xpensive large area feeder electrodes to be used while the dispersed n anoscale electrodes can be a small mass of a high cost electrocatalyst . These studies demonstrate that heterogeneous dispersion electrolyses using electrode-modified zeolites can overcome the difficulties norma lly associated with industrial applications of electrosynthetic scheme s: slow reaction times, difficult electrolyte separations, and high el ectrode costs. (C) 1997 Elsevier Science S.A.