Nickel phthalocyanine integrated graphene architecture as bifunctional electrocatalyst for CO2 and O2 reductions

Abstract

Efficient, durable and low cost electrocatalysts for O2 and CO2 reductions are required as alternate to expensive metal based catalysts in fuel cells and in the CO2 reduction process. Herein, we describe the synthesis of reduced graphene oxide (rGO)-nickel phthalocyanine (NiPc) composite (rGO-NiPc) as a bifunctional electrocatalyst for O2 and CO2 reductions. The composite material, rGO-NiPc is coated on glassy carbon (GC) electrode (GC/rGO-NiPc) and used as a low cost efficient electrocatalyst for O2 and CO2 reductions. The results show that the addition of rGO to NiPc increases the catalytic efficiency and electrochemical charge transfer rate of NiPc. GC/rGO-NiPc provides the low potentials, +0.25 and −0.11 V (vs RHE) for O2 and CO2 reductions, respectively in 0.1 M HClO4. Kinetic interpretation based on rotating disc electrode studies provides the support for the two electron pathway for CO2 reduction to CO in 0.1 M HClO4. Product analysis by 13C NMR confirms CO as the CO2 reduction product. GC/rGO-NiPc shows a facile four electron pathway for O2 reduction which can be exploited in fuel cells, metal-air batteries, chlor-alkali electrolyzers and oxygen sensing. In addition, GC/rGO-NiPc has efficient methanol tolerance capability for O2 reduction process which is suitable to use in fuel cells. Moreover, GC/rGO-NiPc shows the high operational stability more than an hour for both O2 and CO2 reductions in 0.1 M HClO4.