Electrocatalytic Properties Of Metal Phthalocyanine Tetrasulfonate Intercalated In Metal Layered Simple Hydroxides (Metal: Co, Cu, And Zn)

A series of hybrid metal (Zn, Cu, and Co) layered simple hydroxides (LSH) functionalized by surfactants, namely, dodecylsulfonate (DS0) or dodecylsulfate (DS-) and by tetrasulfonato metal (Cu, Co)-phthalocyanines, was synthesized by anionic exchange reactions and characterized by ancillary techniques. The electrochemical properties of these compounds were investigated by cyclic voltammetry in phosphate buffer solutions over a wide potential range including that suitable for oxygen reduction. The electroactivity of intralayer metal cations (Cu and Co) was evidenced as a function of the phosphate buffer pH. The redox properties of Co- and Cu-PcTS0 grafted in LSH (Zn, Co, and Cu) were also investigated in neutral pH solution, under argon, air, or O-2 atmospheres. Interestingly, these hybrid compounds display an electrocatalytic behavior toward the reduction of oxygen. In particular with CoPcTS0-LSH, a sharp electrocatalytic reduction wave is observed at -0.40 V/Ag-AgCl with an intensity that depends on the oxygen concentration. The formation of a CoPc-O-2 grafted species in the presence of oxygen was confirmed by electron paramagnetic resonance spectroscopy.