Atomic layer deposited Al2O3 layer confinement: an efficient strategy to synthesize durable MOF-derived catalysts toward the oxygen evolution reaction

Abstract

Structural collapse and aggregation during the annealing process are the key obstacles for MOF-derived electrocatalysts, which will lead to a decrease in the active site density and stability of the electrocatalyst. The atomic layer deposition (ALD) technique can form dense and uniform thin films wrapping any complex 3D structure due to the self-limiting surface chemistry reactions. Herein, we developed a confinement strategy based on the ALD technique to prepare a durable Fe₂Ni MIL 88-derived electrocatalyst (NiFe/NC@Al₂O₃-2). Due to the protection of the Al₂O₃ layer deposited by the ALD technique, the as-prepared catalyst retained the original rod-like structure of MIL 88 after the annealing process. With the confinement effect of the Al₂O₃ nanolayer, the optimized NiFe/NC@Al₂O₃-2 exhibited remarkable electrocatalytic properties in the oxygen evolution reaction (OER) with low overpotentials of 270 and 391 mV at 10 and 100 mA cm⁻², respectively. Furthermore, the catalyst obtained an excellent durability over 100 hours at a high current density of 50 mA cm⁻², which is superior to those of many previously reported NiFe-based electrocatalysts. The ALD-assisted confinement strategy highlights a novel method to synthesize structure- and morphology-retained MOF-derived catalysts with excellent activity and stability at high current densities.