A Copper(III) Porphyrin Adsorbed on an Indium-Tin Oxide (ITO) Electrode Facilitates Water Oxidation in Aqueous Solutions

Magal Saphier, Chemistry, NRCN, Beer- Sheva, Israel
Dror Shamir, Chemistry, Nrcn, Beer- Sheva, Israel
Oshra Saphier, Chemical Engineering, Sami Shamoon College Of Engineering, Beer- Sheva, Israel
Zeev Gross, Chemistry, Technion, Hifa, Israel

The development of active and robust water-oxidation catalysts is crucial for the creation of artificial photosynthetic devices. The reverse reaction, the reduction of oxygen is most important for fuel cells.   Consequently, the development of active and stable water oxidation/ oxygen reduction catalysts is crucial, using heterogeneous systems.

In light of the fact that Heme–copper oxidase (HCO) catalyses the natural reduction of oxygen to water using a heme-copper centre. Copper porphryins and corrolles adsorbed on the surface can be considered as good candidates for that mission or for water oxidation.    

Following the characterization of Copper(III) tetraphenylporphyrin¹, the latter dissolved in dichloroethane was adsorbed on an ITO electrode surface. To our surprise, the adsorbed Cu(III) tetraphenylporphyrin remains stable in aqueous solutions as Cu(III) tetraphenylporphyrin (according to its known measured UV-vis spectrum) and didn’t react with the water as Cu(III) tetraphenylporphyrin in organic solution or solid state does. Electrochemical studies in aqueous solution of Cu(III)porphyrin on ITO, have point out that water oxidation occurred at a relatively low potential ( a cathodic shift of approximately 0.5 V). Gas analysis has proved the formation of O₂. The system of copper porphrin/ITO were investigated by a set of analytical techniques. We describe herein their electrocatalysts activity, and based on the analytical studies, a plausible mechanism has been evaluated.

1. The Redox Chemistry of Copper tetraphenylporphyrin revisited; J. Porphyrins Phthalocyanines 2012; 16: 2–8