Deposition of Fe3O4 Overlayers on Nickel-Anchored Molybdenum Oxide for Enhanced and Stable Oxygen Evolution Reaction in Alkaline Water Electrolysis

Abstract

Alkaline water electrolysis (AWE) offers a clean and economically competitive solution for large-scale hydrogen production. The efficiency of AWE is often hindered by the sluggish kinetics of the oxygen evolution reaction (OER), which involves complex proton-coupled electron transfer steps. While Ni-Fe hydroxides have emerged as effective OER catalysts, their inherently low conductivity hinders efficient charge transport in micro-meter-scale structures, which benefit from large active surface areas. To overcome this limitation, we present novel Ni-MoO₂ catalysts integrated with a Fe₃O₄ layer, synthesized via a facile co-precipitation method. The synergistic interplay between Ni nanoparticles and MoO₂ layer facilitates charge transfer from Fe₃O₄ overlayer, significantly enhancing OER activity. Additionally, the chemically stable Fe₃O₄ can mitigate the dissolution of Mo from MoO₂, contributing to long-term stability. The Fe₃O₄ overlayer effectively reduces the OER overpotential to 227 mV, a substantial improvement compared to pristine Ni-MoO₂ (272 mV). Notably, the catalyst exhibits exceptional stability, with a negligible overpotential increase of only 1 mV after 100 hours of operation at 100 mA/cm². This work not only highlights the significant enhancement of OER performance by the Fe₃O₄ overlayer but also provides valuable insights into the rational design of highly efficient and durable electrocatalysts for sustainable energy applications.