Tannic Acid-Induced Morphological and Electronic Tuning of Metal-Organic Frameworks Toward Efficient Oxygen Evolution

초록

This study presents a novel dual-temperature synthesis strategy for cobalt, zinc, and iron-based metal-organic frameworks (MOFs) integrated with tannic acid (TA) surface modification to enhance oxygen evolution reaction (OER) performance. MOFs were synthesized at room temperature and 80 degrees C, enabling controlled crystal growth and distinct morphologies. Subsequent TA treatment effectively tuned surface chemistry without altering core crystallinity, as confirmed by PXRD, FT-IR, and XPS analyses. Surface modification introduced oxygen-containing functional groups, improved charge transfer, and increased active-site accessibility. Among the catalysts, the tannic acid-modified Fe-based MOF synthesized at 80 degrees C (TAFeM-2) exhibited outstanding OER activity, achieving an overpotential of only 254 mV at 10 mA cm-2, outperforming benchmark RuO2 (276 mV) and unmodified counterparts. Tafel slope analysis revealed faster reaction kinetics for surface-tuned MOFs, while electrochemical impedance spectroscopy indicated reduced charge-transfer resistance (12 Omega for TAFeM-2). Chronoamperometry demonstrated exceptional long-term stability, maintaining constant current density over 20 h with minimal performance loss. Post-OER characterization suggested surface oxidation to iron oxyhydroxides without significant structural degradation. This work demonstrates that combining dual-temperature synthesis with TA surface engineering yields MOF-based catalysts with superior activity, conductivity, and durability, offering a promising pathway for developing high-performance electrocatalysts for sustainable energy applications.

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