Synergistic Ostwald Ripening Suppression and Organic Acid Ligand Engineering for Micrometer-Scale β-FeOOH Nanorod...

Nanomaterials exhibit unique physicochemical properties that differ from their bulk counterparts, while controlled nanoparticle self-assembly enables collective properties beyond discrete nanostructures. Simultaneously achieving precise nanoscale control and macroscopic structural ordering remains a significant challenge. Herein, a synergistic approach combining Ostwald ripening suppression with organic ligand engineering is presented to achieve micrometer-scale β-FeOOH nanorod arrays. Adding ZnCl₂ and octanoic acid during FeCl₃ hydrothermal hydrolysis is key. ZnCl₂ both limits nanorod growth to sub-50 nm via competitive Zn²⁺/Fe³⁺ complexation, suppressing Ostwald ripening, and promotes oriented self-assembly via [ZnCl₄]^2- complex formation, compressing the electric double layer and enhancing interactions. Octanoic acid aids assembly via surface ligand engineering, enabling large-scale ordered domains. The resulting parallel-aligned nanorod architecture exhibits enhanced stability and promotes enhanced Li⁺ diffusion/charge transfer. As a lithium-ion battery anode, this hierarchical material delivers a high capacity of 2168.9 mAh g^-1 at 1 A g^-1 after 850 cycles, exceeding most reported anodes. This work establishes a generalizable approach for bridging nanoscale precision with macroscopic organization, offering opportunities for designing advanced energy storage materials via programmable assembly.