Enhancing the protection of graphite electrodes against acids by using fullerene/porphyrin composite films

Graphite electrodes in acidic electrolytes suffer significant degradation due to anion interactions near the oxygen evolution potential (OEP), leading to the dissolution of the graphite basal plane. 5,10,15,20-Tetraphenyl21H,23H-porphine (H2TPP) films can protect highly oriented pyrolytic graphite (HOPG) surfaces, as shown by in-situ AFM and electrochemical analysis. Though ultrathin porphyrin films are ineffective due to imperfections on the surface, thicker films, around 25 nm, form nanocrystals which initially protect but degrade over time in acidic environments, acting as a sacrificial layer (i.e., a temporary film allowed to protect a sample and removed after serving its purpose). To enhance protection, we add a fullerene (C60) layer on the H2TPP film, leveraging noncovalent interactions to shield the porphyrin from acid attack. Although fullerenes dissolve in highly concentrated sulfuric acid, they are not affected in diluted H2SO4 electrolytes at potentials where HOPG degrades. Our findings reveal that C60/H2TPP/HOPG electrodes in 1 M H2SO4 exhibit superior protective performance compared to H2TPP/HOPG alone, suggesting that the C60 layer significantly enhances the durability of the porphyrin film, offering a more robust solution for preserving the graphite electrodes under acidic conditions.