Ferric Oxide Nanocrystals‐Embedded Co/Fe‐MOF with Self‐Tuned d‐Band Centers for Boosting Urea‐Assisted Overall Water Splitting

Abstract A novel semiconductive Co/Fe‐MOF embedded with Fe 2 O 3 nanocrystals (Fe 2 O 3 @CoFe‐MOF) is developed as a trifunctional electrocatalyst for the urea oxidation reaction (UOR), oxygen evolution reaction (OER), and hydrogen evolution reaction for enhancing the efficiency of the hydrogen production via the urea‐assisted overall water splitting. Fe 2 O 3 @CoFe‐TPyP‐MOF comprises unsaturated metal‐nitrogen coordination sites, affording enriched defects, self‐tuned d ‐band centers, and efficient π – π interaction between different layers. Density functional theory calculation confirms that the adsorption of urea can be optimized at Fe 2 O 3 @CoFe‐TPyP‐MOF, realizing the efficient adsorption of intermediates and desorption of the final product of CO 2 and N 2 characterized by the in situ Fourier transform infrared spectroscopy. The two‐electrode urea‐assisted water splitting device‐assembled with Fe 2 O 3 @CoFe‐TPyP‐MOF illustrates a low cell voltage of 1.41 V versus the reversible hydrogen electrode at the current density of 10 mA cm −2 , attaining the hydrogen production rate of 13.13 µmol min −1 in 1 m KOH with 0.33 m urea. The in situ electrochemical Raman spectra and other basic characterizations of the used electrocatalyst uncover that Fe 2 O 3 @CoFe‐TPyP‐MOF undergoes the reversible structural reconstruction after the UOR test, while it demonstrates the irreversible reconstruction after the OER measurement. This work redounds the progress of urea‐assisted water spitting for hydrogen production.