Metal–Organic Framework‐Derived Fe/Co‐based Bifunctional Electrode for H 2 Production through Water and Urea Electrolysis

Hollow‐structured Fe x Co 2− x P, Fe x Co 3− x O 4 , 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, Fe x Co 2− 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 Fe x Co 3− x O 4 /NF and FeCo‐PBA/NF demand higher overpotentials. Remarkably, for water electrolysis, Fe x Co 2− 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 Fe x Co 2− 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 H 2 through urea electrolysis needs only 1.42 V to drive 10 mA cm −2 .