Metal–Organic Framework‐Derived Fe/Co‐based Bifunctional Electrode for H2 Production through Water and Urea Electrolysis

: Hollow-structured Fex Co2-x P, Fex Co3-x O4 , and Prussian blue analogue (FeCo-PBA) microbuilding arrays on Ni foam (NF) are derived from Co-based metal-organic frameworks (Co-MOF) using a simple room temperature and post-heat-treatment route. Among them, Fex Co2-x P/NF shows excellent bifunctional catalytic activities by demonstrating very low oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) overpotentials of 255/114 mV at a current density of 20/10 mA cm-2 respectively, whereas Fex Co3-x O4 /NF and FeCo-PBA/NF demand higher overpotentials. Remarkably, for water electrolysis, Fex Co2-x P/NF requires only 1.61 V to obtain 10 mA cm-2 . In contrast to water electrolysis, urea electrolysis reduces overpotential and simultaneously purifies the urea-rich wastewater. The urea oxidation reaction at the Fex Co2-x P/NF anode needs just 1.345 V to achieve 20 mA cm-2 , which is 140 mV less than the 1.48 V potential required for OER. Moreover, the generation of H2 through urea electrolysis needs only 1.42 V to drive 10 mA cm-2 .