Electrochemical reconstruction of metal–organic gels into crystalline oxy-hydroxide heterostructures for efficient oxygen evolution electrocatalysis

Abstract

Metal–organic gels (MOGs) are emerging soft materials with distinct metal active centers, multifunctional ligands and hierarchical porous structures, showing promising potential in the field of electrocatalysis. However, the reconfiguration of MOGs during the electrocatalytic process remains underexplored, with current studies in early developmental stages. To deeply investigate the application of MOG materials in electrocatalysis, the compositional transformations and structural changes under an electrochemical activation method were studied in detail, leading to high-performance OER pre-electrocatalysts. XRD and HRTEM results demonstrate the complete reconfiguration of amorphous Fe₅Ni₅-MOG into crystalline NiOOH/FeOOH heterostructures. The synergistic effect of the bimetallic center and the rich NiOOH–FeOOH interface in the reconstituted Re-Fe₅Ni₅-MOG exhibit excellent OER activity in alkaline electrolytes, with low overpotentials (205 mV at 10 mA cm⁻²) and a Tafel slope of 58 mV dec⁻¹. In situ characterization during the electrocatalytic process reveals the gradual transformation of the metal center into metal hydroxyl oxides upon increasing the voltage to 1.55 V. DFT analysis suggests that in the Fe–Ni double site reaction pathway, active substances preferentially adsorb on the Fe site before the Ni sites.