Synergism effect of CeO2 and Fe3O4 derived from MIL-88 regulating the surface reconstruction to achieve high-performance for overall water splitting

Electrochemical water electrolysis has become a prominent strategy to produce H2 and O2 from renewable sources. Herein, the unique CeO2/Fe3O4-0.2 composite with spindle morphology was synthesized through a hydrothermal and high-temperature calcination method. The CeO2 exhibit a variable chemical valence of Ce4+/Ce3+ and generate much oxygen vacancies through redox reactions. The synergy effect between Fe3O4 and CeO2 leads to increase the number of active sites, accelerate the charge transfer process, and enhance the interface between the electrode and electrolyte. The CeO2/Fe3O4-0.2 displays a low overpotential of 305 mV for oxygen evolution reaction (OER) and 73 mV for the hydrogen evolution reaction (HER) at 10 mA cm-2 in 1 M KOH. Additionally, this composite catalyst exhibits outstanding durability and only a slight potential change observed over 100 h for OER. The cell voltage of electrolysis electrolyzer using CeO2/Fe3O4-0.2 as both anode and cathode is 1.56 V to drive 10 mA cm-2. This research effort delivers a complete advantage for the development of cost-effective and highly active bifunctional catalysts for overall water splitting.