Permanent electrochemical promotion (P-EPOC) of C3H8 oxidation over Pt thin films

S. SOUENTIE; L. LIZARRAGA; E.I. PAPAIOANNOU; P. VERNOUX

Niza

Encuentro; The 61st Annual Meeting of the International Society of Electrochemistry; 2010

International Society of Electrochemistry

The effect of ?permanent electrochemical promotion of catalysis? (P-EPOC) was studied for the first time in the catalytic deep oxidation of C3H8 over a thin (~150 nm) sputtered Pt film on YSZ, under excess oxygen at 350oC. Positive current application (+1V) resulted in a 5.6-fold increase of the catalytic rate, where C3H8 conversion reached 33% and the apparent Faradaic efficiency was ~330. After positive current interruption the catalytic rate remained in a highly active steady-state, determined by the total charge of the anodic polarization step, contrary to previous P-EPOC studies, where the catalyst restores its initial activity after a reasonable relaxation time. Restoration of the catalytic activity to the initial occurred only by a similar negative potential imposition. This new stable steady-state after current interruption has been interpreted by formation of stable PtOx upon anodic polarization at the Pt/YSZ interface and subsequent charge transfer at the Pt/PtOx interface, due to Fermi level equilibration. This induces the migration of O2- species from the electrolyte support to the Pt surface, due to electroneutrality, which increases the work function of Pt. Consequently, the Pt-Oads bond strength weakens and leads to enhanced catalytic activity, establishing a self-driven EPOC mechanism.