Paradoxical effect of the redox potential of adsorbed metallophthalocyanines on their activity for the oxidation of 2-mercaptoethanol. Inner versus outer sphere electrocatalysis
作者： José H. Zagal , Miguel A. Gulppi , Claudia A. Caro , Gloria I. Cárdenas-Jirón
DOI: 10.1016/S1388-2481(99)00076-4
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摘要: Abstract We have studied the effect of redox potential metallophthalocyanines (M-Pcs) adsorbed on graphite their electrocatalytic activity for oxidation 2-mercaptoethanol (ME). This was achieved by: (i) changing metal in phthalocyanine (M-Pc where M=Cr, Mn, Fe, Co, Ni and Cu) (ii) using cobalt phthalocyanines with electron-donor electron-withdrawing substituents macrocyclic ligand. For different metals a plot log k versus catalyst gives straight line slope 0.10 V decade −1 which is close to value obtained (0.12 ) from Tafel plots all M-Pcs investigated. In contrast, when substituted are compared, negative (−0.240 rate decreases driving force. Since ME electrooxidation aqueous media most likely proceeds via an inner-sphere mechanism rate-determining step same investigated, decrease constant force may be due electronic coupling between center sulfur ME. Preliminary PM3 semi-empirical theoretical calculations associated interaction molecule support this explanation.
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