Reducing hole-injection hurdles of OER electrocatalysts derived from Ru-doped FeNi metal–organic frameworks anchored with FeOOH

Abstract

Metal–organic framework (MOF)-based electrocatalysts are considered promising materials for offering the remarkable characteristics of the oxygen evolution reaction (OER) in alkaline electrolytes, whereas the strategies that enable the enhancement of OER performances and reduction of overpotentials restrict the practical assessment of water splitting. Herein, the anchoring of FeOOH nanoparticles on Ru-doped FeNi MOF surfaces was realized via facile and reliable all-solution synthesis, which enables the synergistic triggering of the formation of OER active sites associated with oxygen vacancies and ferrous cations (Fe²⁺) and further serves as a hole mediator that boosts the strong coupling between water electrolytes and catalysts, presenting an explicitly suppressed overpotential of 115 mV at a current density of 100 mA cm⁻². In addition, these heterostructure-based electrocatalysts not only demonstrate an outstanding OER catalytic performance at the anode, but further serve as cost-effective alternatives for effectively triggering the hydrogen evolution reaction (HER) at the cathode. The obtained bi-functional catalyst systems exhibit remarkable operational stability, endowing OER/HER bi-functionalities over 18 000 s at a current density of 100 mA cm⁻² with a Faraday efficiency of 94.60% and a minimal voltage requirement of 1.69 V.