In situ construction of Fe3O4@FeOOH for efficient electrocatalytic urea oxidation

Abstract

Substituting water oxidation half of water splitting with anodic oxidation of urea can reduce the cost of H2 production and provide an avenue for treating urea-rich wastewater. However, developing an efficient and stable electrocatalyst is necessary to overcome the indolent kinetics of the urea oxidation reaction (UOR). Accordingly, we have used the Schikorr reaction to deposit Fe3O4 particles on the nickel foam (Fe3O4/NF). Results from the various analysis indicated that under the operational conditions, Fe3O4 underwent surface reconstruction to produce a heterolayered structure wherein a catalytically active FeOOH layer encased a conducting Fe3O4. Fe3O4/NF outperformed RuO2 as a UOR catalyst and delivered a current density of 10 50 and 100 mA cm−2 at low applied potentials of 1.38 1.42 and 1.46 V, respectively, with a Tafel slope of 28 mV dec−1. At the applied potential of 1.4 V, Fe3O4/NF demonstrated a turnover frequency (TOF) of 2.8 × 10−3 s−1, highlighting its superior intrinsic activity. In addition, a symmetrical urea electrolyzer constructed using Fe3O4/NF produced the current density of 10 mA cm−2 at a cell voltage of 1.54 V.