Significant Reduction of Anode Reaction Overpotential in Alkaline Water Electrolysis by Ultrathin NiFe-Layered Double Hydroxide in Ethanol-Added Electrolyte

Abstract

Electrochemical alkaline water electrolysis (AWE) is regarded as an effective method for producing high-purity hydrogen without relying on platinum group metal (PGM) as catalyst. However, the oxygen evolution reaction (OER), as the anode half-reaction, involves a four-electron transfer process with slow kinetics, which significantly reduces the overall reaction efficiency of AWE. Although highly efficient catalysts can accelerate the OER rate, the high overpotential of the anode still remains an important factor hindering AWE. Herein, ultrathin NiFe-layered double hydroxide (U-NiFe LDH) nanosheet arrays were synthesized and used as anode catalysts due to their robust structure, excellent flexibility, and effective interlayer anion compensation. Only 250 mV of overpotential was required for OER to reach a current density of 10 mA cm⁻² in 1 M KOH. Incorporating the additive ethanol into KOH electrolyte further reduces the required overpotential of AWE to 114 mV. The anode overpotential could be decreased by 130 mV at a current density of 100 mA cm⁻² in a three-electrode electrolysis system with U-NiFe LDH as the anode. This work provides a possible approach for the development of low-energy and green AWE technology for electrocatalytic hydrogen production.