Interfacial Coupling of Gadolinium-2-methylimidazole Metal Organic Framework and 2D-g-C3N4 Nanosheet for Synergistically Enhanced Bifunctional Oxygen Electrocatalysis

Abstract

The excessive cost and scarcity of the noble-metal catalysts needed for catalyzing the bifunctional oxygen evolution and reduction reactions (OER and ORR) for metal-air batteries limit the commercialization of clean-energy technologies. In this work, gadolinium-2-methylimidazole (Gd-2-mim) metal–organic framework-functionalized 2D-graphitic carbon nitride (2D-g-C₃N₄) heterostructure (Gd-2-mim/2D-g-C₃N₄) as a bifunctional electrocatalyst is demonstrated for OER and ORR. The electrocatalyst is synthesized through mixing and coprecipitation methods. The structural, interfacial, thermal, and microstructural properties of the synthesized heterostructure are revealed through several characterizations. A stable nanoporous morphology with improved electrocatalytic active sites and enhanced specific surface area of Gd-2-mim/2D-g-C₃N₄ exhibits the highest onset potential (0.85 V) and lowest charge transfer resistance (R_ct = 96.2 Ω) for ORR and lowest overpotential (59 mV @10 mA cm^–2) for OER with the highest turnover frequency (TOF = 0.42 s^–1). A plausible bifunctional mechanism is portrayed based on the electrocatalytic reaction kinetics. The catalyst is capable of substituting the state-of-the-art electrocatalysts Pt/C and RuO₂ for ORR and OER respectively.