Facile Synthesis of Nonprecious Bimetallic Zeolitic Imidazolate Framework-Based Hierarchical Nanocomposites as Efficient Electrocatalysts for Oxygen Reduction Reaction

Conversion of designer metal–organic frameworks (MOFs) into hybrid nanocomposites (HNCs) consisting of transition metal/metal oxides interfaced with carbon (C) matrices has emerged as a promising and economical alternative for the synthesis of oxygen reduction reaction (ORR) electrocatalysts, owing to their superior conductivity and high porosity. To that end, optimizing the performance of this class of material by tailoring its composition, structure, size, and morphology through an efficient synthesis route has become an active area of research. Specifically, this study employs Laser Ablation Synthesis in Solution in tandem with Galvanic Replacement Reaction (LASiS-GRR) technique as an environmentally friendly, facile, and rapid route for the design and synthesis of core–shell bimetallic zeolitic imidazolate framework (ZIF) heterostructures as bi-MOFs, and then uses pyrolytic postprocessing to yield hierarchical metal oxide/MOF-based functional HNCs as highly active ORR electrocatalysts. The LASiS-GRR technique employs high-energy laser plasma reactions as the rate-controlling step for initiating solution-phase galvanic reactions. The one-pot, two-step process introduced in this study enables tailoring of the composition, structure, size, and morphology of composite bi-MOFs comprising Co-based MOFs encapsulated in Zn-based porous crystals (Co/ZIF-67@Zn/ZIF-8). Pyrolytic postprocessing of these core–shell bi-MOF crystals leads to the creation of hierarchical ZnO@ZIF/C HNCs with superior ORR electrocatalytic performances under alkaline conditions. Overall, these findings not only elucidate the process by which LASiS-GRR protocols are optimized to tailor the morphology, structure, and composition of complex MOF structures but also demonstrate the superior performance and stability of the ensuing postpyrolyzed ZnO@ZIF/C HNCs as nonprecious metal-based ORR electrocatalysts, when compared to commonly used Pt- and Pt-group metal (PGM)-based electrocatalysts.