Growth and electrochemical stability of a layer-by-layer thin film containing tetrasulfonated Fe phthalocyanine

Abstract

Devices based on the functionalization of surfaces with iron phthalocyanine could have potential applications in sensors as well as in clean energy generation. In this work we studied the growth and electrochemical stability of layer-by-layer (LbL) thin films composed of alternating layers of anionic iron tetrasulfonated phthalocyanine (FeTsPc) and cationic polyallylamine (PAH). Atomic force microscopy (AFM) was used to monitor film morphology and X-ray photoelectron spectroscopy (XPS) was used to monitor the film chemical composition. Films grow uniformly increasing their thickness as the number of deposited layers increases. Cyclic voltammetry (CV) was used to determine the electrochemical activity for the oxygen reduction reaction (ORR). Thin films with 1, 3, 5 and 10 FeTsPc/PAH bilayers show similar activities for the ORR after cycling 50 times. Post-electrochemical AFM and XPS show that the film restructures after electrochemical cycling forming deposits with electrochemical activities close to that of a monolayer of FeTsPc. Our results are important for the design of LbL films incorporating catalytically active redox centers.