Hierarchical Co,Fe-MOF-74/Co/Carbon Cloth Hybrid Electrode: Simple Construction and Enhanced Catalytic Performance in Full Water Splitting

Abstract

Metal–organic frameworks (MOFs) have attracted much interest in electrocatalysis as promising catalysts in recent years. However, it still remains a challenge to directly use MOF-based materials as bifunctional electrocatalysts for overall water splitting. Herein, a hierarchical Co,Fe-MOF-74/Co/carbon cloth (CC) three-layer hybrid electrode is synthesized by a simple electrochemical deposition technology with subsequent solvothermal treatment. Electrochemical performance investigations show that the as-constructed Co,Fe-MOF-74/Co/CC electrode exhibits impressive electrocatalytic activity for full water splitting, which only requires a low overpotential of 226 mV@20 mA cm–2 for the oxygen evolution reaction (OER) and 94 mV@–10 mA cm–2 for the hydrogen evolution reaction (HER), respectively. Employing the as-constructed electrode as the anode and cathode in a two-electrode setup simultaneously, only 1.65 V of the voltage is needed to deliver the current density of 20 mA cm–2. The above excellent electrochemical performances should be attributed to the specific architecture, the synergistic effect of the Co and Fe species, and the superhydrophilic surface of the catalyst. More importantly, further investigations uncover that metal hydroxides and oxyhydroxides produced in situ during electrochemical tests are the veritable active species, which promote the high catalytic activity of the present catalyst.