Inverted Linear Correlation Between the Catalytic Activity of Iron Phthalocyanines and the Formal Potential of the Catalyst in the Electrooxidation of l-Cysteine

• DOI: 10.1007/s12678-012-0097-y
• Publication Date: 2012-05-15T23:53:13Z
• Authors: Cristian Gutierrez; J. Francisco Silva; Jorge Pavez; Fethi Bedioui; José H. Zagal
• Keywords: 01 natural sciences; 0104 chemical sciences

The formal potential of macrocyclic complexes is a reactivity index that can serve to predict their electrocatalytic activity. We have investigated the effect of the Fe(II)/(I) formal potential E°′ of several iron phthalocyanines preadsorbed on graphite electrodes on their catalytic activity for the electrooxidation of l-cysteine. A linear and inverted correlation is observed between the catalytic activity (as log I at constant E) versus the Fe(II)/(I) formal potential of the catalyst, i.e., the activity decreases as the driving force of the catalyst increases. The slope of the correlation is close to −2RT/F and seems to be the falling region of an incomplete volcano plot so the decrease of the activity with increasing E°′ can be attributed to a gradual increase in the coverage of l-cysteine molecules adsorbed on the Fe sites with a subsequent decrease in free Fe(II) active sites.