Operando Characterization of Iron Phthalocyanine Deactivation during Oxygen Reduction Reaction Using Electrochemical Tip-Enhanced Raman Spectroscopy

Abstract

Electrochemical tip-enhanced Raman spectroscopy (EC-TERS) has been implemented to investigate the structure and activity of iron(II) phthalocyanine (FePc)a model catalyst for the oxygen reduction reaction (ORR). Using EC-TERS, both reversible change and irreversible degradation to FePc have been observed during ORR. The reversible change in the Raman spectrum of FePc can be related to the FePc molecules that adapt a nonplanar geometry during catalysis. In contrast, the irreversible degradation of FePc is a consequence of FePc demetalation, leading to the subsequent formation of free base phthalocyanine. This observation affirms that FePc demetalation during ORR proceeds via a direct loss of Fe 2+ and that carbon corrosion is not the operative mechanism. Importantly, the FePc demetalation process can be correlated with a loss of ORR activity suggesting that Fe-containing sites are essential for FePc to achieve high catalytic activity. This study establishes EC-TERS as a promising technique for the operando characterization of electrocatalytic reactions at the molecular scale.

Tuning the Covering on Gold Surfaces by Grafting Amino-Aryl Films Functionalized with Fe(II) Phthalocyanine: Performance on the Electrocatalysis of Oxygen Reduction

“…ORR on gold is known to proceed only via two electrons to give peroxide [35,36], so the voltametric response corresponds to a total transfer of two electrons. On the other hand, it is important to note that modified electrodes with FePc in alkaline media catalyze the ORR preferentially via the four-electron pathway to give water, as shown in the literature [17,19,20,34,37]. Therefore, the enhancement of electron transfers kinetics (catalytic currents) due to the presence of anchored FePc is through the effect on the general mechanism of the reaction.…”

“…Today, nonprecious metal catalysts have become an excellent alternative to replace platinum. Among them are the MN4 macrocycle catalysts like Fe(II) and Co(II) phthalocyanines [17][18][19][20][21] or porphyrins [22][23][24].…”

Conversion of CO2 into Chloropropene Carbonate Catalyzed by Iron (II) Phthalocyanine Hypercrosslinked Porous Organic Polymer

“…A partial elimination of nickel in a NiPc was achieved by halogenation using NaBr followed by addition of oxone solution [ 26 ], whereas ZnPc was also partially demetaled under a mixture of pyridine and HCl at 120 °C for several hours [ 27 ]. Recently, it was observed that iron was lost in a FePc during an oxygen reaction reduction process [ 28 ]. However, when iron containing POPs were used in ORR reactions by us [ 29 ], no iron loss was observed, which proves the high metal stability of these materials.…”

In Situ and Operando Techniques for Investigating Electron Transfer in Biological Systems

“…Electrochemical tip‐enhanced Raman scattering (EC‐TERS) microscopy is an emerging technique that combines scanning probe microscopy with Raman spectroscopy under electrochemical control conditions and is therefore well suited for probing redox reactions [93,94] . However, this technique has not yet been applied to bioelectrochemical systems.…”