Organic hybrid of cobalt phthalocyanine embedded graphene as an efficient catalyst for oxygen reduction reaction

Abstract

The widespread practical applications of the fuel cells are dependent on the rational development of state-of-the-art easily synthesizable or earth-abundant catalysts for oxygen reduction reaction (ORR). This work demonstrates the utilization of cobalt phthalocyanine polymer (pCoPc) encased graphene (Gr) layer with an extensive π-π interaction as a proficient and non-precious electrocatalyst for ORR. The synthesized material is characterized by UV–vis, IR, Mass, NMR, SEM, TEM and XPS techniques. The fabricated Gr-pCoPc catalyst exhibited significant enhancement in the ORR performance which is comparable to the benchmark Pt/C catalyst with a decent durability in alkaline media. More importantly, the ORR onset potential at Gr-pCoPc shifted towards the positive potential by 10 mV compared to the Pt/C catalyst. The enhancement observed in the ORR performance and stability of the Gr-pCoPc catalyst could be attributed to the combined impact created by the outstanding electronic and conductive attributes of graphene, along with the π-stacking interactions inherent in pCoPc. In comparison to prior catalysts in literature and Pt/C, Gr-pCoPc displayed a notably lower Tafel slope of 64 mV dec-1 and larger double layer capacitance, Cdl value of 9.5 mF cm−2. The RDE experiments indicated that the hybrid composite of Gr-pCoPc facilitated an effective 4-electron pathway during ORR. Gr-pCoPc catalyst is highly durable towards ORR and it retained > 92.5 % of its initial ORR activity even after 5000 repeated cycles.