Elucidating the distinct roles of metal ion doping and alloying in MOF reconstruction toward enhanced oxygen evolution reaction
Amorphous metal-organic frameworks (aMOFs), with abundant defects and unsaturated coordination sites, are ideal precursors for investigating electrocatalytic reconstruction mechanisms. However, systematic understanding of how different modulation strategies affect reconstruction pathways and final active species remains lacking. Here, an amorphous MOF constructed from 3,4,9,10-pyrene-tetracarboxylic acid (PTA) serves as a controllable precursor to compare doping and alloying effects on structural reconstruction and oxygen evolution reaction (OER) performance. Doping promotes preferential reconstruction into Fe-rich (oxy)hydroxides with more exposed active sites, whereas alloying yields Fe-Co mixed (oxy)hydroxides with limited site exposure. The doped system FeCo0.05-PTA exhibits outstanding OER activity in alkaline conditions, with overpotentials of 208 and 248 mV at 50 and 100 mA cm−2, respectively, and a low Tafel slope of 36.2 mV dec−1. In situ Fourier transform infrared spectroscopy (FTIR) captures the OOH* intermediate, confirming the adsorbate evolution mechanism. Density functional theory (DFT) calculations show the doped system has the lowest free-energy barrier (ΔG = 0.59 eV) at the rate-determining step. This study underscores the decisive role of precursor design, elucidates distinct effects of doping and alloying on reconstruction pathways and final properties of amorphous MOF-derived (oxy)hydroxides, and provides insights for designing related electrocatalysts.