Defect‐Mediated In Situ CNT Growth in Hollow Porous Carbon From ZIF‐8/ZIF‐67 Bilayers for Efficient and Stable ORR Catalysis

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Abstract The rational design of carbon‐based electrocatalysts with hierarchical porosity, graphitic domains, and optimized active sites is crucial for advancing the oxygen reduction reaction (ORR). Herein, a bilayer core‐shell ZIF (PS@BCZ)‐derived strategy is presented that enables the in situ growth of carbon nanotubes (CNTs) and uniform embedding of cobalt nanoparticles (Co NPs) within an N‐doped hollow porous carbon matrix (CNT‐Co/N‐HPC). Sequential ZIF‐8/ZIF‐67 growth on polystyrene spheres, followed by pyrolysis, induces Zn sublimation from the ZIF‐8 layer, generating structural defects that promote CNT formation and facilitate the uniform dispersion of Co catalytic sites. Molecular dynamics simulations reveal that Zn‐induced defect environments are critical for triggering CNT growth in the presence of Co catalysts. The optimized CNT‐Co/N‐HPC(1/20) exhibited excellent ORR performance, achieving a half‐wave potential of 0.864 V (vs RHE) and a diffusion‐limited current density of 5.35 mA cm −2 in alkaline media, comparable to commercial Pt/C. The catalyst demonstrated outstanding long‐term durability (98.9% retention after 10 h, and only a slight 8 mV negative shift in half‐wave potential after 5000 potential cycles) and strong tolerance to methanol. This study elucidates the role of Zn‐induced defects in directing CNT growth and highlights a tunable ZIF‐derived strategy for engineering efficient carbon‐based ORR catalysts.

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