(118i) Rational Synthesis, Morphology, and Propertyrelationship of Non-Precious Bi-Metallic Hybridnanocomposites for Improving Oxygen Reductionreactions

Tailored metal oxide/metal-organic frameworks (MOFs) can readily be converted to hybrid nanocomposites (HNCs) comprised of transition metals interfaced with carbon (C) matrices. To that end, this class of nanocomposites (NCs) that exhibit superior conductivity and high porosity are promising and economically viable candidates as oxygen reduction reaction (ORR) electrocatalysts. Hence, optimizing the performance of this class of material by tailoring their composition, structure, size, and morphology through an efficient synthesis process has increasingly become an active area of research. In this study, we report the use of Laser Ablation Synthesis in Solution in Tandem with Galvanic Replacement Reaction (LASiS-GRR) technique as a facile, environmentally friendly, and rapid route for the synthesis and control of complex hierarchical bimetallic Zeolitic Imidazolate Framework (ZIF) structures, and their pyrolytic post-processing to yield metal oxide/MOF-based functional HNCs as highly active ORR electrocatalysts. The LASiS-GRR technique utilizes high-energy laser plasma reactions as the rate-controlling step for the initiation of solution-phase galvanic reactions. The one-pot, two-step process introduced in this study allows tailoring of the composition, structure, size, and morphology of the Co-based MOFs encapsulated in Zn-based porous MOF (Co/ZIF- 67@Zn/ZIF-8) crystals. Pyrolytic post-processing of these crystals leads to the creation of HNCs with superior functionality for ORR electrocatalysts for anion exchange membrane fuel cells (AEMFCs). Specifically, herein, for the first time, we demonstrate the use of the LASiS-GRR technique as a one-pot rational synthesis method for synthesizing
Co/ZIF-67@Zn/ZIF-8 bi-MOFs that, upon post-pyrolytic treatments are converted into unique tailored HNCs of ZnO-interfaced ZIF-67 in carbonaceous matrices (ZnO/ZIF@C). Not only the effect of two distinct salt precursors on the particle size and morphology is investigated for the first time during LASiS, but also the superior performance and stability of these ZnO/ZIF@C HNCs as non-precious metal ORR electrocatalysts compared to commonly used Pt- and platinum-group metals (PGM)-based electrocatalysts in AEMFC applications is demonstrated.