Phthalocyanine based metal-organic frame work with carbon nanoparticles as hybrid catalyst for oxygen reduction reaction

Abstract

Lot of research efforts are on way to overcome the sluggish kinetics of oxygen reduction reaction (ORR) and to replace the expensive Pt/C catalyst employed at the cathode of a fuel cell. Organic macrocycles are being investigated extensively as suitable replacement for Pt/C as their properties can be tuned easily by changing the substituents. In this regard, a novel metal-organic framework of cobalt acridinedione phthalocyanine (CoIITADPc) is synthesized in pure state with good yield. The spectroscopic characterization as well as electrochemical activity of the synthesized complex is carried out. CoIITADPc is administered on a glassy carbon electrode (GCE) and evaluated for the ORR. The scanning electron microscope (SEM) images displayed uniform distribution of CoIITADPc and hybrid composite of CoIITADPc with Ketjen black carbon nanoparticles (KB-CNP) on the electrode surface. The pristine CoIITADPc and hybrid composite electrodes are evaluated for ORR in an oxygen saturated alkaline medium, and the mechanism is understood using a rotating disk electrode (RDE). The hybrid catalyst displayed an onset potential of 0.85 V vs. reversible hydrogen electrode (RHE) which is one of the best values for the reported organic-based catalysts and is very close to Pt/C benchmark catalyst (0.9 V vs. RHE). The excellent ORR activity of the organic hybrid composite catalyst is due to the higher surface area, conductivity, ring-based or metal-based electron transfer processes as well as efficient π-π interaction. The hybrid catalyst displayed a cathodic ORR response with 4-electron transfer. In addition, the composite catalyst showed remarkable stability and has all the unique properties to replace Pt/C for practical applications.