3D Porous Ru-Doped NiCo-MOF Hollow Nanospheres for Boosting Oxygen Evolution Reaction Electrocatalysis

Developing high-performance and cost-efficient catalysts toward oxygen evolution reaction (OER) is an important but daunting task due to the sluggish kinetics hindered by the four-electron transfer process. Herein, an advanced class of ultralow Ru-doped NiCo-MOF hollow porous nanospheres (denoted as Ru@NiCo-MOF HPNs) has been reported in this work. Benefiting from the high porosity and large surface area of the metal-organic frameworks (MOFs) and optimized electronic properties by Ru doping, the as-prepared Ru@NiCo-MOF HPNs exhibit superior performance for water oxidation with the overpotential of only 284 mV to reach a current density of 10 mA·cm^-2 in alkaline electrolyte, as well as a small Tafel slope of 78.8 mV·dec^-1, outperforming the NiCo-MOF HPNs (358 mV) and commercial RuO₂ catalyst (326 mV). The incorporation of Ru in NiCo-MOF HPNs enables a stable OER activity for at least 39 h. Moreover, we have probed the interaction between the content of Ru and OER performance, impressively, Ru@NiCo-MOF HPNs with 13.5 atom % Ru doping (denoted as Ru@NiCo-MOF-4) exhibited the highest OER activity with the excellent mass activity of 310 mA·mg^-1 at an overpotential of 284 mV. Besides, a two-electrode cell with Ru@NiCo-MOF-4 as the anode and commercial Pt/C catalyst as the cathode also demonstrated outstanding electrocatalytic overall water splitting performance with a cell potential of merely 1.57 V to deliver a current density of 10 mA·cm^-2.