Construction of CeO2/Co(OH)2/FeS@NF nanosheet arrays for high-performance electrocatalytic oxygen evolution/urea oxidation, and overall water/urea splitting reactions

To develop non-noble electrocatalysts with high activity and stability for oxygen evolution reaction (OER)/urea oxidation reaction (UOR) is crucial to boost the efficiency of overall water/urea splitting reaction (OWS/OUS) for H₂ production. Herein, we synthesized novel CeO₂/Co(OH)₂/FeS nanosheet arrays on nickel foam (CeO₂/Co(OH)₂/FeS@NF) through a simple two-step hydrothermal and following solvothermal routine. In this special structure, the ultra-thin 2D nanosheet morphology can adequately offer large contact area and thus abundant of active sites, facilitating significantly the mass transfer. Furthermore, the incorporation of FeS into CeO₂/Co(OH)₂ will not only modify the electron structure but also provide a number of phase interfaces, which can improve the inherent electron conductivity and promote the electron transport. More importantly, the rich oxygen vacancies (O_v) sites can vary the coordination of metal centers, modulating both the charge distribution and M−O bonding strength. As results, the CeO₂/Co(OH)₂/FeS@NF shows superior low overpotentials of 178 mV/1.30 V at 10 mA cm⁻² to OER/UOR. The activity keeps its low value of 232 mV/1.375 V even when the current density was increased to as high as 300 mA cm⁻². More importantly, the electrode of CeO₂/Co(OH)₂/FeS@NF//CeO₂/Co(OH)₂/FeS@NF just requires a low cell voltage of 1.41 V to realize OUS at a current density of 10 mA cm⁻². Specifically, we also realized solar-driven H₂ production. Plenty of H₂ bubbles were continuously generated with a high speed of 600 L h⁻¹ m⁻² on the working electrode surface once the solar panel was placed under the natural sunlight.