Expeditious electrodeposition of bimetallic hydroxide/oxide as pre-catalysts for water electrolyzer applications and unveiling its phase change by operando Raman spectroscopy

Abstract

Designing noble metal-free and high electrocatalytic materials via facile and cost-effective routes has garnered great importance in the production of hydrogen. Herein, we fabricated nickel hydroxide-iron oxide (NiFe) composite material without any surfactants by an expeditious, one-step, and cost-effective electrodeposition technique. For a short deposition time of 150 s, the NiFe material (NiFe-150) was directly synthesized on Ni foam into thin nanosheets. Comprising the structural merits of hierarchical connection, open nanochannels, and superior active area, the NiFe-150 catalyst unveiled excellent catalytic activity toward oxygen evolution reaction (OER) in the alkaline medium. With the minimal overpotential of 128 mV, the NiFe-150 catalyst showed the current density of 10 mA cm(-2) and achieved 400 mA cm(-2) for 659 mV. The Tafel slope was also smaller, i.e., 45 mV dec(-1), than the other catalysts. Moreover, the NiFe-150 catalyst revealed good catalytic stability for 24 h. To gain a deep insight into the phase change, the in situ/operando Raman analysis of the NiFe-150 catalyst was performed during its real-time OER measurement and confirmed the conversion of the initial phase into metal (oxy)hydroxides. An anion-exchange membrane water electrolyzer cell was then constructed with the NiFe-150 and Pt/C catalysts as anode and cathode, respectively. The full cell also exhibited a notable water electrolysis performance by driving a high current density of similar to 1100 mA cm(-2). This study may shed light on the fabrication of cost-effective and noble-metal-free catalysts by simple, low-cost, and expeditious preparation routes for high-performance water electrolyzer.