Template-Assisted Fabrication of ZnO/Co₃O₄ One-Dimensional Metal–Organic Framework Array Decorated with Amorphous Iron Oxide/Hydroxide Nanoparticles as an Efficient Electrocatalyst for the Oxygen Evolution Reaction

The construction of new electrocatalysts for effective and low-cost water electrolysis continues to be an important conceptual barrier for clean renewable energy technologies. Herein, we fabricate a unique approach to a stable metal–organic framework (MOF) based on zinc oxide/cobalt oxide (MOF ZnO/Co 3 O 4 ) array synthesis aided by a sacrificial template technique and followed by the decoration of three-dimensional MOF arrays using amorphous iron oxide/hydroxide (FeOOH) nanoparticles. The highly active FeOOH nanoparticles are tightly bound to the surface of the MOF ZnO/Co 3 O 4 array. These integrated heterostructures provide copious active sites, a large electrochemical surface area, an effective charge-mass transfer, and a strong integration between MOF ZnO/Co 3 O 4 and FeOOH nanoparticles. Ascribed to all such aspects, FeOOH @ MOF ZnO/Co 3 O 4 nanorods supported on nickel foam show an oxygen evolution reaction activity order of magnitude higher than that of individual entities in an alkaline solution with an overpotential of 260 mV achieved at a current density of 50 mA·cm –2 and a Tafel slope of 48 mV dec –1 . This behavior can be ascribed to the effect of amorphous FeOOH nanoparticles being tightly anchored on the MOF ZnO/Co 3 O 4 surface, which not only synergistically enriches the electrochemical surface area but also enhances the active sites. This work offers to open a new strategy to design and fabricate advanced electrode materials for the water electrolysis process.