Enzyme-Like Catalytic Activity of Porphyrin-Functionalized Ceria Nanotubes for Water Oxidation

Artificial enzymes have broad applications in catalysis and can be used to help understand catalytic mechanisms. Nanoceria has various enzyme-mimetic properties that depend on the relative content of Ce³⁺ and Ce⁴⁺ . In this context, CeO₂ nanotubes was investigated as catalase mimics for water oxidation. The photosensitizer 5,10,15,20-meso-tetra(4-carboxyphenyl) porphyrin (TCPP) was facilely embedded in CeO₂ nanotubes (TCPP@CeO₂ NTs), and photoinduced charge transfer was shown to occur between the strongly coupled TCPP and CeO₂ , which leads to effective charge separation and charge redistribution within the hybrids. As a consequence, formation of H₂ O₂ , a competing process in water oxidation and a key factor that affects the oxidative stability of photoelectrodes, was effectively inhibited on TCPP@CeO₂ NTs. These findings show that enzyme mimics can be used for the selective generation of reactive oxygen species, and therefore to control the kinetics of water oxidation.