Insights into the electronic structure of Fe penta-coordinated complexes. Spectroscopic examination and electrochemical analysis for the oxygen reduction and oxygen evolution reactions

César Zúñiga Loyola , Gabriel Abarca , Soledad Ureta-Zañartu , Carolina Aliaga , Jose H Zagal , Moulay Tahar Sougrati (1) , Frederic Jaouen (1) , Walter Orellana , Federico Tasca

1 ICGM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier

Fe phthalocyanine was coordinated to pyridine-modified carbon nanotubes and studied as a catalyst for the oxygen reduction (ORR) and oxygen evolution reactions (OER). X-ray Photoelectron Spectroscopy (XPS), Mössbauer, and Electron Paramagnetic Resonance spectroscopy (EPR) analysis supported that pyridine acts as an axial ligand to yield penta-coordinated catalytic active Fe sites. The impedance analyses show an increase in the double-layer capacitance (Cdl) value, corroborating the adsorption of the complexes to give FePc-Py-CNT. The evaluation of the electrocatalytic activity for the ORR was performed in both acid (0.1 M H2SO4) and basic (0.1 M KOH) media, while the evaluation of the OER activity was investigated only in alkaline medium. DFT studies revealed an increased length in the Fe-N binding of the pentacoordinate Fe-based site, leading to a decreased O2-Fe binding energy, explaining the higher ORR and OER activity of FePc-Py-CNT relative to FePc-CNT.

Domaines: Catalyse

César Zúñiga Loyola, Gabriel Abarca, Soledad Ureta-Zañartu, Carolina Aliaga, Jose H Zagal, et al.. Insights into the electronic structure of Fe penta-coordinated complexes. Spectroscopic examination and electrochemical analysis for the oxygen reduction and oxygen evolution reactions. Journal of Materials Chemistry A, 2021, 9 (42), pp.23802-23816. ⟨10.1039/D1TA05991B⟩. ⟨hal-03364957⟩