Poly-tetrakis-5,10,15,20-(4-aminophenyl)porphyrin Films as Two-Electron Oxygen Reduction Photoelectrocatalysts for the Production of H₂O₂

Abstract

Thin films of electropolymerized porphyrin polymers, poly-tetrakis-5,10,15,20-(4-aminophenyl)porphyrin (pTAPP) and its cobalt derivative (pCoTAPP), were found to be electrocatalysts and photoelectrocatalysts for the photosynthesis of hydrogen peroxide via a two-electron reduction of oxygen. On glassy carbon (GC) electrodes, oxygen reduction potentials were measured at −0.58 (GC), −0.40 (pTAPP), and −0.05 V (pCoTAPP), compared to Pt at +0.34 V (all vs Ag/AgCl). Thin electrode films were tested as photosynthetic electrocatalysts using small positive bias potentials (0.0 to +0.3 V) and specifically measuring H2O2 production. pTAPP achieved turnover numbers (TON) of 5–6, while pCoTAPP showed TON of 14–23. Faradaic efficiency in both cases was initially high, about 50%, but decreased over 1 h.