Vertically Oriented FeNiO Nanosheet Array for Urea and Water Electrolysis at Industrial-Scale Current Density

Abstract

In addressing the challenging quest for an efficient electrocatalyst in electrochemical water splitting, we demonstrate an Fe-doped NiO nanosheet array anchored on nickel foam synthesized via a two-step process. Demonstrating exceptional performance in an alkaline electrolyte, FeNiO catalysts exhibit the oxygen evolution reaction with a low potential of 1.52 V vs RHE and the urea oxidation reaction of 1.32 V vs RHE @ 10 mA/cm 2 . The bifunctional electrolyzer generates 10 mA/cm 2 current at 1.95 V for water and 1.59 V for urea electrolysis at ambient temperature. Promisingly, the FeNiO catalyst based electrolyzer generates hydrogen at an industrial-scale current density of 400 mA/cm 2 at a cell voltage of just 1.91 V in concentrated alkaline electrolyte and elevated temperature (80 °C) due to the dimensionally stable and robust behavior of the self-supported catalyst. The activation energy for alkaline water electrolysis is found to be 52 kJ/mol. The present catalysts also demonstrate stable performance at 300 mA/cm 2 in 4 M KOH electrolyte at 50 °C for more than 20 h. The synergy induced by Fe doping into NiO activates catalytic sites, expediting charge transfer and reaction kinetics. The present research report highlights the potential of catalysts as a practical and cost-effective approach for green hydrogen production via water splitting.