Component regulation on ternary FeCoNi nano-bundles as efficient electrocatalysts for driving water oxidation

Metal organic frameworks (MOFs) are considered as promising electrocatalytic materials due to their tunable porosity, functional organic ligands, and large specific surface area for oxygen evolution reaction (OER). Recently, most reported electrocatalysts focus on the establishing heterogeneous structures by thermal treatments to improve OER performance. However, the thermal treatments are accompanied by the complex synthetic process and destruction of the MOFs structure. Therefore, improving the catalytic performance of pristine MOFs remains a challenge. Here, a series of trimetallic M_aM_bM_c-MOFs (M represents metal element) were synthesized by one-pot method. Modulating the Co/Ni ratio not only adjusts the morphology of FeCoNi-MOFs, but also effectively optimizes the electronic structure. The composition-optimized FeCo_0.5Ni_2.5-MOF nano-bundles (FeCo_0.5Ni_2.5-NBs) only required a low overpotential of 273 mV to achieve the current density of 10 mA cm^-2 in alkaline solution, with a Tafel slope of 51.1 mV dec^-1, lower than other FeCoNi-MOFs and commercial RuO₂ catalyst. The two-electrode couple FeCo_0.5Ni_2.5-NBs || Pt/C achieved the cell voltage of 1.55 V, delivering current density of 10 mA cm^-2 for overall water splitting.