Electrocatalysis of cathodic oxygen reduction by metal phthalocyanines

Metallophthalocyanine-based molecular materials as catalysts for electrochemical reactions

“…In a study involving heat treated 4(Ph)FeP [415] and deposited by thick layers on glassy carbon, the amount of hydrogen peroxide decomposed, compared to the amount of oxygen and hydrogen peroxide reduced, was so small that chemical decomposition was ruled out. van den Brink et al [413] have found that for vacuum deposited layers of FePc the first reduction wave scan was very different from subsequent scans, indicating that some reorganization of the deposited layers took place (this phenomenon is not observed on From ref. [414] with permission from Elsevier.…”

“…This interaction prevents peroxide from desorbing as a two-electron reduction product. So essentially these studies show that adsorbed hydrogen peroxide is an intermediate formed from FeN4-OOH on Fe(II) sites and can be released into the solution at more negative potentials as found experimentally [366,413].…”

“…Indeed for some metal chelates van Veen and van Baar have shown that their catalytic activity for hydrogen peroxide decomposition is directly proportional to their activity for O 2 reduction [412]. It was suggested for FePc and 4␤(SO 3 − )FePc that dioxygen can bind to the Fe center and to a highly electronegative nitrogens in the ring, which will avoid the desorption of hydrogen peroxide before it is reduced [241,369,410,413]. This dual site mechanism would aid charge injection via back-bonding from the macrocycle into antibonding orbitals of O 2 or bound hydrogen peroxide, causing the destabilization and further rupture of the O-O bond [414].…”

Electrochemical reduction of oxygen with iron phthalocyanine in neutral media

“…It has been reported that iron phthalocyanine (FePc) has the ability to promote direct 4e -oxygen reduction to water, while CoPc promotes O 2 reduction to H 2 O 2 by a 2e -pathway [27][28][29]. This 4e -pathway is more desirable as it avoids the production of hydrogen peroxide which can damage the electrode structure.…”

A new method of preparing a rotating ring-disc electrode for the study of carbon supported catalysts

“…With respect to the selectivity, this behaviour is the same as that of vacuum evaporated CoPc and FePc films in alkaline solution [9,10], although the FePc/BRX electrode here produces relatively more H,O,; the activity in alkaline solution is higher.…”