(569cq) Investigating the Electrochemical Activity of FeMoO4 Catalyst for Alkaline Water Electrolysis

Electrochemical water splitting emerges as a pivotal strategy for sustainable hydrogen production, with alkaline water electrolysis offering a promising pathway for generating pure hydrogen. However, the efficiency of this process is hindered by the sluggish kinetics of the anodic oxygen evolution reaction (OER), necessitating the development of efficient water oxidation electrocatalysts. This research addresses the pressing need by investigating the electrochemical activity of FeMoO₄, aiming to overcome the limitations posed by costly and scarce catalysts like RuO₂ and IrO₂. Through a detailed electrochemical study, FeMoO₄ catalysts synthesized via a hydrothermal synthesis method supported over Nickel Foam (NF) were analyzed. Characterization techniques including X-ray diffraction and scanning electron microscopy were employed, revealing nanosheets agglomerated nanospheres of FeMoO₄ moieties, providing a large surface area for OER. The results demonstrate that FeMoO₄ exhibits favorable surface adsorption-desorption kinetics, attributed to its electronic structure, facilitating efficient electrocatalysis. Raman analysis post OER tests reveal a potential-driven hydrolytic dissolution process, separating [MoO₄]^2‑ from FeMoO₄ and resulting in the formation of FeO(OH) as the electroactive species. The deficient lattice stability (indicated by formation enthalpy; ΔH_f), inadequate Fe−O−Mo bonding strength, and low decomposition enthalpy (ΔH_D) within the FeMoO₄ lattice promote an easy electrocatalytic decomposition process, leading to the formation of the highly reactive FeO(OH) surface as observed in the variable temperature OER study, imposes a rate-limiting step on the formation of peroxo (O−O) bonds. Cyclic voltammetry measurements present an overpotential of 228 and 315 mV at 10 and 1000 mA/cm² respectively which is much lower than recently reported a noble metal oxide electrocatalyst like IrO₂/NF (290 mV at 10 mA/cm²), indicating its potential as a cost-effective alternative. This combined experimental and theoretical study emphasizes the crucial role of the material's electronic structure, particularly the interaction between the anionic counterpart and the active metal, in influencing OER activity.