Electron Shuttling of Iron-Oxygen-Cobalt Bridging in Cobalt Assembled Iron Oxyhydroxide Catalyst Boosts the Urea Oxidation Stability and Activity

Abstract

Iron (Fe)-based materials hold great potential as urea oxidation reaction (UOR) catalysts, however, the deactivation of active Fe-oxyhydroxide (FeOOH) species induced by its dissolution during catalytic process under high current densities is still significant challenge. Herein, cobalt (Co) assembled FeOOH is constructed, and the formation of Iron-Oxygen-Cobalt (Fe-O-Co) bridging triggers the electron transfer from Co to Fe sites. This electron shuttling induces the low valence state of Fe active sites in FeOOH. This Co-FeOOH catalyst achieves a current density of 1000 mA cm⁻² at a low voltage of merely 1.59 V, showing a substantial improvement compared to pure FeOOH (1.97 V). Meanwhile, in the urea-assisted anion exchange membrane electrolyzer, after 24 h continuous operation at a current density of 1000 mA cm⁻², the voltage fluctuation of Co-FeOOH is merely 12.4%, significantly lower than that of FeOOH (49.9%). The in situ experiments and theoretical calculations demonstrate the electron transfer from Co to Fe sites in Fe-O-Co bridging endows the suppressive Fe-segregation, fast charge transfer of active Fe(Co)OOH phase and negative-shifted d-band center of metal active sites, boosting its UOR stability and activity.